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1.
  • Ahlfors, Reetta, et al. (författare)
  • Arabidopsis RADICAL-INDUCED CELL DEATH1 belongs to the WWE protein-protein interaction domain protein family and modulates abscisic acid, ethylene, and methyl jasmonate responses.
  • 2004
  • Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 16:7, s. 1925-37
  • Tidskriftsartikel (refereegranskat)abstract
    • Experiments with several Arabidopsis thaliana mutants have revealed a web of interactions between hormonal signaling. Here, we show that the Arabidopsis mutant radical-induced cell death1 (rcd1), although hypersensitive to apoplastic superoxide and ozone, is more resistant to chloroplastic superoxide formation, exhibits reduced sensitivity to abscisic acid, ethylene, and methyl jasmonate, and has altered expression of several hormonally regulated genes. Furthermore, rcd1 has higher stomatal conductance than the wild type. The rcd1-1 mutation was mapped to the gene At1g32230 where it disrupts an intron splice site resulting in a truncated protein. RCD1 belongs to the (ADP-ribosyl)transferase domain–containing subfamily of the WWE protein–protein interaction domain protein family. The results suggest that RCD1 could act as an integrative node in hormonal signaling and in the regulation of several stress-responsive genes.
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2.
  • Bollhoner, Benjamin, et al. (författare)
  • Xylem cell death : emerging understanding of regulation and function
  • 2012
  • Ingår i: Journal of Experimental Botany. - : Oxford University Press. - 0022-0957 .- 1460-2431. ; 63:3, s. 1081-1094
  • Forskningsöversikt (refereegranskat)abstract
    • Evolutionary, as well as genetic, evidence suggests that vascular development evolved originally as a cell death programme that allowed enhanced movement of water in the extinct protracheophytes, and that secondary wall formation in the water-conducting cells evolved afterwards, providing mechanical support for effective long-distance transport of water. The extant vascular plants possess a common regulatory network to coordinate the different phases of xylem maturation, including secondary wall formation, cell death, and finally autolysis of the cell contents, by the action of recently identified NAC domain transcription factors. Consequently, xylem cell death is an inseparable part of the xylem maturation programme, making it difficult to uncouple cell death mechanistically from secondary wall formation, and thus identify the key factors specifically involved in regulation of cell death. Current knowledge suggests that the necessary components for xylem cell death are produced early during xylem differentiation, and cell death is prevented through the action of inhibitors and storage of hydrolytic enzymes in inactive forms in compartments such as the vacuole. Bursting of the central vacuole triggers autolytic hydrolysis of the cell contents, which ultimately leads to cell death. This cascade of events varies between the different xylem cell types. The water-transporting tracheary elements rely on a rapid cell death programme, with hydrolysis of cell contents taking place for the most part, if not entirely, after vacuolar bursting, while the xylem fibres disintegrate cellular contents at a slower pace, well before cell death. This review includes a detailed description of cell morphology, function of plant growth regulators, such as ethylene and thermospermine, and the action of hydrolytic nucleases and proteases during cell death of the different xylem cell types.
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3.
  • Bollhöner, Benjamin, 1980-, et al. (författare)
  • Post mortem function of AtMC9 in xylem vessel elements
  • 2013
  • Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 200:2, s. 498-510
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell death of xylem elements is manifested by rupture of the tonoplast and subsequent autolysis of the cellular contents. Metacaspases have been implicated in various forms of plant cell death but regulation and execution of xylem cell death by metacaspases remains unknown. Analysis of the type II metacaspase gene family in Arabidopsis thaliana supported the function of METACASPASE 9 (AtMC9) in xylem cell death. Progression of xylem cell death was analysed in protoxylem vessel elements of 3-d-old atmc9 mutant roots using reporter gene analysis and electron microscopy. Protoxylem cell death was normally initiated in atmc9 mutant lines, but detailed electron microscopic analyses revealed a role for AtMC9 in clearance of the cell contents post mortem, that is after tonoplast rupture. Subcellular localization of fluorescent AtMC9 reporter fusions supported a post mortem role for AtMC9. Further, probe-based activity profiling suggested a function of AtMC9 on activities of papain-like cysteine proteases. Our data demonstrate that the function of AtMC9 in xylem cell death is to degrade vessel cell contents after vacuolar rupture. We further provide evidence on a proteolytic cascade in post mortem autolysis of xylem vessel elements and suggest that AtMC9 is part of this cascade.
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4.
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5.
  • Bollhöner, Benjamin, 1980- (författare)
  • Significance of hydrolytic enzymes expressed during xylem cell death
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Xylem is an inherent feature of all vascular plants and functions in water transport and mechanical support. In order to efficiently transport water, xylem cells are reinforced by secondary walls before they undergo programmed cell death and their cell contents are removed by autolysis to create a hollow tube. During their differentiation, xylem cells express various hydrolytic enzymes, such as proteases, nucleases and lipases, but only in a few examples has their role in xylem cell death been characterized. This thesis focuses on the regulatory aspects of xylem cell death and the autolytic cell clearance in vessel elements and fibers of hybrid aspen (Populus tremula L. x tremuloides Michx.) and in vessel elements of Arabidopsis thaliana. Using comparative transcriptomic analysis, candidate genes for fiber-specific cell death processes were identified. Further, a hypothesis is presented on the regulation of thermospermine levels in the vasculature by a negative feedback-loop involving auxin and the class III Homeodomain-Leucine Zipper (HD-ZIP III) transcription factor HOMEOBOX8 (PtHB8). The role of the Arabidopsis METACASPASE9 (AtMC9) in xylem cell death was characterized using molecular tools, such as reporter lines and fluorescent fusion proteins, and electron microscopy (TEM). This showed that cell death initiation is not controlled by AtMC9. Instead, evidence is presented for the involvement of AtMC9 in the post mortem autolysis of vessel elements that follows tonoplast rupture and leads to the formation of the hollow conduit. Cell death-associated genes were further observed to be expressed during the emergence of lateral roots in Arabidopsis thaliana. This led to the discovery that cells overlying a lateral root primordium undergo cell death, which was demonstrated by detection of DNA degradation and TEM analysis. It is concluded that cell death facilitates emergence of lateral roots through the overlying tissues in a concerted manner with cell wall remodelling. Together, these findings show that although individual hydrolytic enzymes may be dispensable for plant growth and development, their common regulators are the tool for understanding their function and importance.
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6.
  • Bollhöner, Benjamin, et al. (författare)
  • The function of two type II metacaspases in woody tissues of Populus trees
  • 2018
  • Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 217:4, s. 1551-1565
  • Tidskriftsartikel (refereegranskat)abstract
    • Metacaspases (MCs) are cysteine proteases that are implicated in programmed cell death of plants. AtMC9 (Arabidopsis thaliana Metacaspase9) is a member of the Arabidopsis MC family that controls the rapid autolysis of the xylem vessel elements, but its downstream targets in xylem remain uncharacterized. PttMC13 and PttMC14 were identified as AtMC9 homologs in hybrid aspen (Populustremulaxtremuloides). A proteomic analysis was conducted in xylem tissues of transgenic hybrid aspen trees which carried either an overexpression or an RNA interference construct for PttMC13 and PttMC14. The proteomic analysis revealed modulation of levels of both previously known targets of metacaspases, such as Tudor staphylococcal nuclease, heat shock proteins and 14-3-3 proteins, as well as novel proteins, such as homologs of the PUTATIVE ASPARTIC PROTEASE3 (PASPA3) and the cysteine protease RD21 by PttMC13 and PttMC14. We identified here the pathways and processes that are modulated by PttMC13 and PttMC14 in xylem tissues. In particular, the results indicate involvement of PttMC13 and/or PttMC14 in downstream proteolytic processes and cell death of xylem elements. This work provides a valuable reference dataset on xylem-specific metacaspase functions for future functional and biochemical analyses.
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7.
  • Chantreau, Maxime, et al. (författare)
  • Spatio-temporal regulation of lignification
  • 2022
  • Ingår i: Advances in Botanical Research. - : Elsevier. - 0065-2296. ; 104, s. 271-316
  • Forskningsöversikt (refereegranskat)abstract
    • Lignin is a poly-aromatic polymer found in plant cell walls. This polymer, mainly composed of three phenylpropanoid units, confers exceptional properties to the cell wall such as hydrophobicity, mechanical strength, or resistance against stresses. Thereby the cell wall deposition of lignin represents often the main molecular event that defines the biological function(s) of the lignified cell or tissue. The time and localization of lignin deposition as well as the composition of the polymer can be considered as the three essential components of the polymer that will define the biological function of the lignified tissue. In this review, we will cover the localizations, types and functions of lignin found in various part of land plants. Then, for the various lignified tissues, the mechanisms controlling the developmental deposition of lignin such as transcriptional regulation, intercellular coordinated control of lignification or posttranslational modification of proteins will be discussed. Finally, a focus will be made on the environmental cues that influence the lignification during radial tree growth, as well as the plant responses that these signals trigger in the regulation of lignification.
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8.
  • Chen, Zhi-Qiang, et al. (författare)
  • Genetic architecture behind developmental and seasonal control of tree growth and wood properties in Norway spruce
  • 2022
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 13
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetic control of tree growth and wood formation varies depending on the age of the tree and the time of the year. Single-locus, multi-locus, and multi-trait genome-wide association studies (GWAS) were conducted on 34 growth and wood property traits in 1,303 Norway spruce individuals using exome capture to cover similar to 130K single-nucleotide polymorphisms (SNPs). GWAS identified associations to the different wood traits in a total of 85 gene models, and several of these were validated in a progenitor population. A multilocus GWAS model identified more SNPs associated with the studied traits than single-locus or multivariate models. Changes in tree age and annual season influenced the genetic architecture of growth and wood properties in unique ways, manifested by non-overlapping SNP loci. In addition to completely novel candidate genes, SNPs were located in genes previously associated with wood formation, such as cellulose synthases and a NAC transcription factor, but that have not been earlier linked to seasonal or age-dependent regulation of wood properties. Interestingly, SNPs associated with the width of the year rings were identified in homologs of Arabidopsis thaliana BARELY ANY MERISTEM 1 and rice BIG GRAIN 1, which have been previously shown to control cell division and biomass production. The results provide toots for future Norway spruce breeding and functional studies.
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9.
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10.
  • Courtois-Moreau, Charleen L, et al. (författare)
  • A unique program for cell death in xylem fibers of Populus stem
  • 2009
  • Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 58:2, s. 260-274
  • Tidskriftsartikel (refereegranskat)abstract
    • Maturation of the xylem elements involves extensive deposition of secondary cell-wall material and autolytic processes resulting in cell death. We describe here a unique type of cell-death program in xylem fibers of hybrid aspen (Populus tremula x P. tremuloides) stems, including gradual degradative processes in both the nucleus and cytoplasm concurrently with the phase of active cell-wall deposition. Nuclear DNA integrity, as determined by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and Comet (single-cell gel electrophoresis) assays, was compromised early during fiber maturation. In addition, degradation of the cytoplasmic contents, as detected by electron microscopy of samples fixed by high-pressure freezing/freeze substitution (HPF-FS), was gradual and resulted in complete loss of the cytoplasmic contents well before the loss of vacuolar integrity, which is considered to be the moment of death. This type of cell death differs significantly from that seen in xylem vessels. The loss of vacuolar integrity, which is thought to initiate cell degradative processes in the xylem vessels, is one of the last processes to occur before the final autolysis of the remaining cell contents in xylem fibers. High-resolution microarray analysis in the vascular tissues of Populus stem, combined with in silico analysis of publicly available data repositories, suggests the involvement of several previously uncharacterized transcription factors, ethylene, sphingolipids and light signaling as well as autophagy in the control of fiber cell death.
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11.
  • Courtois-Moreau, Charleen, Laetitia, 1978- (författare)
  • Programmed Cell Death in Xylem Development
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Concerns about climate changes and scarcity of fossil fuels are rising. Hence wood is becoming an attractive source of renewable energy and raw material and these new dimensions have prompted increasing interest in wood formation in trees, in both the scientific community and wider public. In this thesis, the focus is on a key process in wood development: programmed cell death (PCD) in the development of xylem elements. Since secondary cell wall formation is dependent, inter alia, upon the life time of xylem elements, the qualitative features of wood will be affected by PCD in xylem, about which there is little information. This thesis focuses on the anatomical, morphological and transcriptional features of PCD during xylem development in both the stem of hybrid aspen, Populus tremula (L.) x tremuloides (Michx.) and the hypocotyl of the herbaceous model system Arabidopsis thaliana (L. Heynh.). In Populus, the progressive removal of organelles from the cytoplasm before the time of death (vacuolar bursts) and the slowness of the cell death process, illustrated by DNA fragmentation assays (such as TUNEL and Comet assays), have been ascertained in the xylem fibres by microscopic analyses. Furthermore, candidate genes for the regulation of fibre cell death were identified either from a Populus EST library obtained from woody tissues undergoing fibre cell death or from microarray experiments in Populus stem, and further assessed in an in silico comparative transcriptomic analysis of Arabidopsis thaliana. These candidate genes were either putative novel regulators of fibre cell death or members of previously described families of cell death-related genes, such as autophagy-related genes. The induction of the latter and the previous microscopic observations suggest the importance of autophagy in the degradation of the cytoplasmic contents specifically in the xylem fibres. Vacuolar bursts in the vessels were the only previously described triggers of PCD in the xylem, which induce the very rapid degradation of the nuclei and surrounding cytoplasmic contents, therefore unravelling a unique previously unrecorded type of PCD in the xylem fibres, principally involving autophagy. Arabidopsis is an attractive alternative model plant for exploring some aspects of wood formation, such as the characterisation of negative regulators of PCD. Therefore, the anatomy of Arabidopsis hypocotyls was also investigated and the ACAULIS5 (ACL5) gene, encoding an enzyme involved in polyamine biosynthesis, was identified as a key regulator of xylem specification, specifically in the vessel elements, though its negative effect on the cell death process. Taken together, PCD in xylem development seems to be a highly specific process, involving unique cell death morphology and molecular machinery. In addition, the technical challenges posed by the complexity of the woody tissues examined highlighted the need for specific methods for assessing PCD and related phenomena in wood.
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12.
  • Escamez, Sacha, et al. (författare)
  • A collection of genetically engineered Populus trees reveals wood biomass traits that predict glucose yield from enzymatic hydrolysis
  • 2017
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Wood represents a promising source of sugars to produce bio-based renewables, including biofuels. However, breaking down lignocellulose requires costly pretreatments because lignocellulose is recalcitrant to enzymatic saccharification. Increasing saccharification potential would greatly contribute to make wood a competitive alternative to petroleum, but this requires improving wood properties. To identify wood biomass traits associated with saccharification, we analyzed a total of 65 traits related to wood chemistry, anatomy and structure, biomass production and saccharification in 40 genetically engineered Populus tree lines. These lines exhibited broad variation in quantitative traits, allowing for multivariate analyses and mathematical modeling. Modeling revealed that seven wood biomass traits associated in a predictive manner with saccharification of glucose after pretreatment. Four of these seven traits were also negatively associated with biomass production, suggesting a trade-off between saccharification potential and total biomass, which has previously been observed to offset the overall sugar yield from whole trees. We therefore estimated the "total-wood glucose yield" (TWG) from whole trees and found 22 biomass traits predictive of TWG after pretreatment. Both saccharification and TWG were associated with low abundant, often overlooked matrix polysaccharides such as arabinose and rhamnose which possibly represent new markers for improved Populus feedstocks.
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13.
  • Escamez, Sacha, 1987-, et al. (författare)
  • Cell Death in Cells Overlying Lateral Root Primordia Facilitates Organ Growth in Arabidopsis
  • 2020
  • Ingår i: Current Biology. - : Elsevier. - 0960-9822 .- 1879-0445. ; 30:3, s. 455-464
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant organ growth is widely accepted to be determined by cell division and cell expansion, but, unlike that in animals, the contribution of cell elimination has rarely been recognized. We investigated this paradigm during Arabidopsis lateral root formation, when the lateral root primordia (LRP) must traverse three overlying cell layers within the parent root. A subset of LRP-overlying cells displayed the induction of marker genes for cell types undergoing developmental cell death, and their cell death was detected by electron, confocal, and light sheet microscopy techniques. LRP growth was delayed in cell-deathdeficient mutants lacking the positive cell death regulator ORESARA1/ANAC092 (ORE1). LRP growth was restored in ore1-2 knockout plants by genetically inducing cell elimination in cells overlying the LRP or by physically killing LRP-overlying cells by ablation with optical tweezers. Our results support that, in addition to previously discovered mechanisms, cell elimination contributes to regulating lateral root emergence.
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14.
  • Escamez, Sacha, et al. (författare)
  • Contribution of cellular autolysis to tissular functions during plant development
  • 2017
  • Ingår i: Current opinion in plant biology. - : CURRENT BIOLOGY LTD. - 1369-5266 .- 1879-0356. ; 35, s. 124-130
  • Forskningsöversikt (refereegranskat)abstract
    • Plant development requires specific cells to be eliminated in a predictable and genetically regulated manner referred to as programmed cell death (PCD). However, the target cells do not merely die but they also undergo autolysis to degrade their cellular corpses. Recent progress in understanding developmental cell elimination suggests that distinct proteins execute PCD sensu stricto and autolysis. In addition, cell death alone and cell dismantlement can fulfill different functions. Hence, it appears biologically meaningful to distinguish between the modules of PCD and autolysis during plant development.
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15.
  • Escamez, Sacha, 1987-, et al. (författare)
  • Extracellular peptide Kratos restricts cell death during vascular development and stress in Arabidopsis
  • 2019
  • Ingår i: Journal of Experimental Botany. - : Oxford University Press. - 0022-0957 .- 1460-2431. ; 70:7, s. 2199-2210
  • Tidskriftsartikel (refereegranskat)abstract
    • During plant vascular development, xylem tracheary elements (TEs) form water-conducting, empty pipes by genetically regulated cell death. Cell death is prevented from spreading to non-TEs by unidentified intercellular mechanisms, downstream of METACASPASE9 (MC9)-mediated regulation of autophagy in TEs. Here, we identified differentially abundant extracellular peptides in vascular-differentiating wild-type and MC9-down-regulated Arabidopsis cell suspensions. A peptide named Kratos rescued the abnormally high ectopic non-TE death resulting from either MC9 knockout or TE-specific overexpression of the ATG5 autophagy protein during experimentally induced vascular differentiation in Arabidopsis cotyledons. Kratos also reduced cell death following mechanical damage and extracellular ROS production in Arabidopsis leaves. Stress-induced but not vascular non-TE cell death was enhanced by another identified peptide, named Bia. Bia is therefore reminiscent of several known plant cell death-inducing peptides acting as damage-associated molecular patterns. In contrast, Kratos plays a novel extracellular cell survival role in the context of development and during stress response.
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16.
  • Escamez, Sacha, 1987-, et al. (författare)
  • Genetic markers and tree properties predicting wood biorefining potential in aspen (Populus tremula) bioenergy feedstock
  • 2023
  • Ingår i: Biotechnology for Biofuels and Bioproducts. - : BioMed Central Ltd. - 2731-3654. ; 16:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Wood represents the majority of the biomass on land and constitutes a renewable source of biofuels and other bioproducts. However, wood is recalcitrant to bioconversion, raising a need for feedstock improvement in production of, for instance, biofuels. We investigated the properties of wood that affect bioconversion, as well as the underlying genetics, to help identify superior tree feedstocks for biorefining. Results: We recorded 65 wood-related and growth traits in a population of 113 natural aspen genotypes from Sweden (https://doi.org/10.5061/dryad.gtht76hrd). These traits included three growth and field performance traits, 20 traits for wood chemical composition, 17 traits for wood anatomy and structure, and 25 wood saccharification traits as indicators of bioconversion potential. Glucose release after saccharification with acidic pretreatment correlated positively with tree stem height and diameter and the carbohydrate content of the wood, and negatively with the content of lignin and the hemicellulose sugar units. Most of these traits displayed extensive natural variation within the aspen population and high broad-sense heritability, supporting their potential in genetic improvement of feedstocks towards improved bioconversion. Finally, a genome-wide association study (GWAS) revealed 13 genetic loci for saccharification yield (on a whole-tree-biomass basis), with six of them intersecting with associations for either height or stem diameter of the trees. Conclusions: The simple growth traits of stem height and diameter were identified as good predictors of wood saccharification yield in aspen trees. GWAS elucidated the underlying genetics, revealing putative genetic markers for bioconversion of bioenergy tree feedstocks. © 2023, The Author(s).
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17.
  • Escamez, Sacha, 1987-, et al. (författare)
  • METACASPASE9 modulates autophagy to confine cell death tothe target cells during Arabidopsis vascular xylem differentiation
  • 2016
  • Ingår i: Biology Open. - : The Company of Biologists ltd. - 2046-6390. ; 5:2, s. 122-129
  • Tidskriftsartikel (refereegranskat)abstract
    • We uncovered that the level of autophagy in plant cells undergoingprogrammed cell death determines the fate of the surrounding cells.Our approach consisted of using Arabidopsis thaliana cell culturescapable of differentiating into two different cell types: vasculartracheary elements (TEs) that undergo programmed cell death(PCD) and protoplast autolysis, and parenchymatic non-TEs thatremain alive. The TE cell type displayed higher levels of autophagywhen expression of the TE-specific METACASPASE9 (MC9) wasreduced using RNAi (MC9-RNAi). Misregulation of autophagy in theMC9-RNAi TEs coincided with ectopic death of the non-TEs, implyingthe existence of an autophagy-dependent intercellular signallingfrom within the TEs towards the non-TEs. Viability of the non-TEswas restored when AUTOPHAGY2 (ATG2) was downregulatedspecifically in MC9-RNAi TEs, demonstrating the importance ofautophagy in the spatial confinement of cell death. Our resultssuggest that other eukaryotic cells undergoing PCD might also needto tightly regulate their level of autophagy to avoid detrimentalconsequences for the surrounding cells.
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18.
  • Escamez, Sacha, et al. (författare)
  • Programmes of cell death and autolysis in tracheary elements : when a suicidal cell arranges its own corpse removal
  • 2014
  • Ingår i: Journal of Experimental Botany. - : Oxford University Press. - 0022-0957 .- 1460-2431. ; 65:5, s. 1313-1321
  • Forskningsöversikt (refereegranskat)abstract
    • Differentiation of tracheary elements (TEs) is finalized by programmed cell death (PCD) and autolysis. This review integrates TE differentiation, PCD, and autolysis in a biological and evolutionary context.Tracheary element (TE) differentiation represents a unique system to study plant developmental programmed cell death (PCD). TE PCD occurs after deposition of the secondary cell walls when an unknown signal induces tonoplast rupture and the arrest of cytoplasmic streaming. TE PCD is tightly followed by autolysis of the protoplast and partial hydrolysis of the primary cell walls. This review integrates TE differentiation, programmed cell death (PCD), and autolysis in a biological and evolutionary context. The collective evidence from the evolutionary and molecular studies suggests that TE differentiation consists primarily of a programme for cell death and autolysis under the direct control of the transcriptional master switches VASCULAR NAC DOMAIN 6 (VND6) and VND7. In this scenario, secondary cell walls represent a later innovation to improve the water transport capacity of TEs which necessitates transcriptional regulators downstream of VND6 and VND7. One of the most fascinating features of TEs is that they need to prepare their own corpse removal by expression and accumulation of hydrolases that are released from the vacuole after TE cell death. Therefore, TE differentiation involves, in addition to PCD, a programmed autolysis which is initiated before cell death and executed post-mortem. It has recently become clear that TE PCD and autolysis are separate processes with separate molecular regulation. Therefore, the importance of distinguishing between the cell death programme per se and autolysis in all plant PCD research and of careful description of the morphological, biochemical, and molecular sequences in each of these processes, is advocated.
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19.
  • Escamez, Sacha, 1987-, et al. (författare)
  • Quick histochemical staining methods to detect cell death in xylem elements of plant tissues
  • 2017. - 1
  • Ingår i: Xylem. - New York : Humana Press. - 9781493967209 - 9781493967223 ; , s. 27-36
  • Bokkapitel (refereegranskat)abstract
    • Histochemical assays of xylem cell death cannot take advantage of the conventional methods for detection of cell death, such as staining with propidium iodide or trypan/Evans blue or the TUNEL staining. This chapter presents two alternative histochemical methods that can be used to detect xylem cell death quickly and reliably using light microscopy. The first method is a viability stain that can be used to detect cell death of different types of xylem elements in basically any plant species. The second method reveals cell death in xylem vessel elements based on their functionality in transport of water and small water-soluble stains.
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20.
  • Escamez, Sacha, 1987- (författare)
  • Xylem cells cooperate in the control of lignification and cell death during plant vascular development
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The evolutionary success of land plants was fostered by the acquisition of the xylem vascular tissue which conducts water and minerals upwards from the roots. The xylem tissue of flowering plants is composed of three main types of cells: the sap-conducting tracheary elements (TE), the fibres which provide mechanical support and the parenchyma cells which provide metabolic support to the tissue. Both the TEs and the fibres deposit thick polysaccharidic secondary cell walls (SCWs), reinforced by a rigid phenolic polymer called lignin. The cell walls of TEs form efficient water conducting hollow tubes after the TEs have undergone programmed cell death (PCD) and complete protoplast degradation as a part of their differentiation. The work presented in this thesis studied the regulation of TE PCD by characterizing the function of the candidate PCD regulator METACASPASE 9 (MC9) in Arabidopsis thaliana xylogenic cell suspensions. These cell suspensions can be externally induced to differentiate into a mix of TEs and parenchymatic non-TE cells, thus representing an ideal system to study the cellular processes of TE PCD. In this system, TEs with reduced expression of MC9 were shown to have increased levels of autophagy and to trigger the ectopic death of the non-TE cells. The viability of the non-TE cells could be restored by down-regulating autophagy specifically in the TEs with reduced MC9 expression. Therefore, this work showed that MC9 must tightly regulate the level of autophagy during TE PCD in order to prevent the TEs from becoming harmful to the non-TEs. Hence, this work demonstrated the existence of a cellular cooperation between the TEs and the surrounding parenchymatic cells during TE PCD. The potential cooperation between the TEs and the neighbouring parenchyma during the biosynthesis of lignin was also investigated. The cupin domain containing protein PIRIN2 was found to regulate TE lignification in a non-cell autonomous manner in Arabidopsis thaliana. More precisely, PIRIN2 was shown to function as an antagonist of positive transcriptional regulators of lignin biosynthetic genes in xylem parenchyma cells. Part of the transcriptional regulation by PIRIN2 involves chromatin modifications, which represent a new type of regulation of lignin biosynthesis. Because xylem constitutes the wood in tree species, this newly discovered regulation of non-cell autonomous lignification represents a potential target to modify lignin biosynthesis in order to overcome the recalcitrance of the woody biomass for the production of biofuels.
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21.
  • Fracheboud, Yvan, et al. (författare)
  • The control of autumn senescence in European aspen
  • 2009
  • Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 149:4, s. 1982-1991
  • Tidskriftsartikel (refereegranskat)abstract
    • The initiation, progression, and natural variation of autumn senescence in European aspen (Populus tremula) was investigated by monitoring chlorophyll degradation in (1) trees growing in natural stands and (2) cloned trees growing in a greenhouse under various light regimes. The main trigger for the initiation of autumn senescence in aspen is the shortening photoperiod, but there was a large degree of variation in the onset of senescence, both within local populations and among trees originating from different populations, where it correlated with the latitude of their respective origins. The variation for onset of senescence with a population was much larger than the variation of bud set. Once started, autumn senescence was accelerated by low temperature and longer nights, and clones that started to senescence late had a faster senescence. Bud set and autumn senescence appeared to be under the control of two independent critical photoperiods, but senescence could not be initiated until a certain time after bud set, suggesting that bud set and growth arrest are important for the trees to acquire competence to respond to the photoperiodic trigger to undergo autumn senescence. A timetable of events related to bud set and autumn senescence is presented.
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22.
  • Gandla, Madhavi Latha, et al. (författare)
  • Overexpression of vesicle-associated membrane protein PttVAP27-17 as a tool to improve biomass production and the overall saccharification yields in Populus trees
  • 2021
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 14:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Bioconversion of wood into bioproducts and biofuels is hindered by the recalcitrance of woody raw material to bioprocesses such as enzymatic saccharification. Targeted modification of the chemical composition of the feedstock can improve saccharification but this gain is often abrogated by concomitant reduction in tree growth. Results In this study, we report on transgenic hybrid aspen (Populus tremula x tremuloides) lines that showed potential to increase biomass production both in the greenhouse and after 5 years of growth in the field. The transgenic lines carried an overexpression construct for Populus tremula x tremuloides vesicle-associated membrane protein (VAMP)-associated protein PttVAP27-17 that was selected from a gene-mining program for novel regulators of wood formation. Analytical-scale enzymatic saccharification without any pretreatment revealed for all greenhouse-grown transgenic lines, compared to the wild type, a 20-44% increase in the glucose yield per dry weight after enzymatic saccharification, even though it was statistically significant only for one line. The glucose yield after enzymatic saccharification with a prior hydrothermal pretreatment step with sulfuric acid was not increased in the greenhouse-grown transgenic trees on a dry-weight basis, but increased by 26-50% when calculated on a whole biomass basis in comparison to the wild-type control. Tendencies to increased glucose yields by up to 24% were present on a whole tree biomass basis after acidic pretreatment and enzymatic saccharification also in the transgenic trees grown for 5 years on the field when compared to the wild-type control. Conclusions The results demonstrate the usefulness of gene-mining programs to identify novel genes with the potential to improve biofuel production in tree biotechnology programs. Furthermore, multi-omic analyses, including transcriptomic, proteomic and metabolomic analyses, performed here provide a toolbox for future studies on the function of VAP27 proteins in plants.
  •  
23.
  • Giacomello, Stefania, et al. (författare)
  • High spatial resolution profiling in tree species
  • 2019
  • Ingår i: Annual Plant Reviews Online. - : Wiley. - 2639-3832. ; 2:1, s. 329-359
  • Tidskriftsartikel (refereegranskat)abstract
    • Until recently, the majority of genomics assays have been performed on bulk tissue samples containing multiple cell types. Tissues such as the wood formation zone in trees contain a complex mix of cell types organised in three-dimensional space. Moreover, cells within the wood formation zone represent a continual developmental progression from meristematic cambial initials through to cell death. This spatiotemporal developmental gradient and cell type information are not assayed by bulk samples. New and improved sampling methods coupled to next-generation sequencing assays are enabling the generation of high spatial resolution and single-cell transcriptomics data, offering unprecedented insight into the biology of unique cell types and cell developmental programs.We overview the application of these approaches to the study of wood development, in particular, and highlight challenges associated with the analysis of such data.
  •  
24.
  • Jokipii-Lukkari, Soile, et al. (författare)
  • NorWood : a gene expression resource for evo-devo studies of conifer wood development
  • 2017
  • Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 216:2, s. 482-494
  • Tidskriftsartikel (refereegranskat)abstract
    • The secondary xylem of conifers is composed mainly of tracheids that differ anatomically and chemically from angiosperm xylem cells. There is currently no high-spatial-resolution data available profiling gene expression during wood formation for any coniferous species, which limits insight into tracheid development.RNA-sequencing data from replicated, high-spatial-resolution section series throughout the cambial and woody tissues of Picea abies were used to generate the NorWood.conGenIE.org web resource, which facilitates exploration of the associated gene expression profiles and co-expression networks.Integration within PlantGenIE.org enabled a comparative regulomics analysis, revealing divergent co-expression networks between P. abies and the two angiosperm species Arabidopsis thaliana and Populus tremula for the secondary cell wall (SCW) master regulator NAC Class IIB transcription factors. The SCW cellulose synthase genes (CesAs) were located in the neighbourhoods of the NAC factors in A. thaliana and P. tremula, but not in P. abies. The NorWood co-expression network enabled identification of potential SCW CesA regulators in P. abies.The NorWood web resource represents a powerful community tool for generating evo-devo insights into the divergence of wood formation between angiosperms and gymnosperms and for advancing understanding of the regulation of wood development in P. abies.
  •  
25.
  • Jokipii-Lukkari, Soile, et al. (författare)
  • Transcriptional Roadmap to Seasonal Variation in Wood Formation of Norway Spruce
  • 2018
  • Ingår i: Plant Physiology. - : American Society of Plant Biologists. - 0032-0889 .- 1532-2548. ; 176:4, s. 2851-2870
  • Tidskriftsartikel (refereegranskat)abstract
    • Seasonal cues influence several aspects of the secondary growth of tree stems, including cambial activity, wood chemistry, and transition to latewood formation. We investigated seasonal changes in cambial activity, secondary cell wall formation, and tracheid cell death in woody tissues of Norway spruce (Picea abies) throughout one seasonal cycle. RNA sequencing was performed simultaneously in both the xylem and cambium/phloem tissues of the stem. Principal component analysis revealed gradual shifts in the transcriptomes that followed a chronological order throughout the season. A notable remodeling of the transcriptome was observed in the winter, with many genes having maximal expression during the coldest months of the year. A highly coexpressed set of monolignol biosynthesis genes showed high expression during the period of secondary cell wall formation as well as a second peak in midwinter. This midwinter peak in expression did not trigger lignin deposition, as determined by pyrolysis-gas chromatography/mass spectrometry. Coexpression consensus network analyses suggested the involvement of transcription factors belonging to the ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES and MYELOBLASTOSIS-HOMEOBOX families in the seasonal control of secondary cell wall formation of tracheids. Interestingly, the lifetime of the latewood tracheids stretched beyond the winter dormancy period, correlating with a lack of cell death-related gene expression. Our transcriptomic analyses combined with phylogenetic and microscopic analyses also identified the cellulose and lignin biosynthetic genes and putative regulators for latewood formation and tracheid cell death in Norway spruce, providing a toolbox for further physiological and functional assays of these important phase transitions.
  •  
26.
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27.
  • Keech, Olivier, et al. (författare)
  • The different fate of mitochondria and chloroplasts during dark-induced senescence in Arabidopsis leaves
  • 2007
  • Ingår i: Plant, Cell and Environment. - Oxford : Blackwell Scientific Publications Ltd. - 0140-7791 .- 1365-3040. ; 30:12, s. 1523-1534
  • Tidskriftsartikel (refereegranskat)abstract
    • Senescence is an active process allowing the reallocation of valuable nutrients from the senescing organ towards storage and/or growing tissues. Using Arabidopsis thaliana leaves from both whole darkened plants (DPs) and individually darkened leaves (IDLs), we investigated the fate of mitochondria and chloroplasts during dark-induced leaf senescence. Combining in vivo visualization of fates of the two organelles by three-dimensional reconstructions of abaxial parts of leaves with functional measurements of photosynthesis and respiration, we showed that the two experimental systems displayed major differences during 6 d of dark treatment. In whole DPs, organelles were largely retained in both epidermal and mesophyll cells. However, while the photosynthetic capacity was maintained, the capacity of mitochondrial respiration decreased. In contrast, IDLs showed a rapid decline in photosynthetic capacity while maintaining a high capacity for mitochondrial respiration throughout the treatment. In addition, we noticed an unequal degradation of organelles in the different cell types of the senescing leaf. From these data, we suggest that metabolism in leaves of the whole DPs enters a ‘stand-by mode’ to preserve the photosynthetic machinery for as long as possible. However, in IDLs, mitochondria actively provide energy and carbon skeletons for the degradation of cell constituents, facilitating the retrieval of nutrients. Finally, the heterogeneity of the degradation processes involved during senescence is discussed with regard to the fate of mitochondria and chloroplasts in the different cell types.
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28.
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29.
  • Lakehal, Abdellah, et al. (författare)
  • ETHYLENE RESPONSE FACTOR 115 integrates jasmonate and cytokinin signaling machineries to repress adventitious rooting in Arabidopsis
  • 2020
  • Ingår i: New Phytologist. - : Wiley-Blackwell Publishing Inc.. - 0028-646X .- 1469-8137. ; 228, s. 1611-1626
  • Tidskriftsartikel (refereegranskat)abstract
    • Adventitious root initiation (ARI) is ade novoorganogenesis program and a key adaptive trait in plants. Several hormones regulate ARI but the underlying genetic architecture that integrates the hormonal crosstalk governing this process remains largely elusive. In this study, we use genetics, genome editing, transcriptomics, hormone profiling and cell biological approaches to demonstrate a crucial role played by the APETALA2/ETHYLENE RESPONSE FACTOR 115 transcription factor. We demonstrate that ERF115 functions as a repressor of ARI by activating the cytokinin (CK) signaling machinery. We also demonstrate thatERF115is transcriptionally activated by jasmonate (JA), an oxylipin-derived phytohormone, which represses ARI in NINJA-dependent and independent manners. Our data indicate that NINJA-dependent JA signaling in pericycle cells blocks early events of ARI. Altogether, our results reveal a previously unreported molecular network involving cooperative crosstalk between JA and CK machineries that represses ARI.
  •  
30.
  • Menard, Delphine, et al. (författare)
  • Life beyond death : the formation of xylem sap conduits
  • 2015
  • Ingår i: Plant programmed cell death. - Cham : Springer. - 9783319210339 - 9783319210322 - 9783319352015 ; , s. 55-76
  • Bokkapitel (refereegranskat)abstract
    • Xylem is the vascular tissue conducting water and minerals in plants. The conduction of the hydro-mineral sap in this tissue is enabled by specific conduit cells named tracheary elements (TEs). These vascular cells undergo a distinct differentiation programme which requires programmed cell death (PCD) to functionalise the cell for sap conduction: PCD empties the cell lumen leaving a hollow corpse delimited only by its cell wall to form the future vascular cylinder. In contrast to many other cell types, PCD initiates the 'physiological life' of TEs to enable the cell to conduct the hydro-mineral sap. This central role of PCD appeared as the first distinct differentiation event of TE ancestor cells during plant evolution. Breakthrough studies combining real-time live-cell imaging and TE differentiation in cell suspension cultures enabled to define the temporal succession of the pre-mortem TE differentiation events - cellulose and hemicellulose depositions in the secondary cell wall - and the post-mortem events including cell wall lignification and the clearing of the residual protoplast. The coordination between these different events and the exact timing of PCD is controlled by specific signalling molecules. 
  •  
31.
  • Milhinhos, Ana, et al. (författare)
  • ACAULIS5 Is Required for Cytokinin Accumulation and Function During Secondary Growth of Populus Trees
  • 2020
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • In the primary root and young hypocotyl of Arabidopsis, ACAULIS5 promotes translation of SUPPRESSOR OF ACAULIS51 (SAC51) and thereby inhibits cytokinin biosynthesis and vascular cell division. In this study, the relationships between ACAULIS5, SAC51 and cytokinin biosynthesis were investigated during secondary growth of Populus stems. Overexpression of ACAULIS5 from the constitutive 35S promoter in hybrid aspen (Populus tremula x Populus tremuloides) trees suppressed the expression level of ACAULIS5, which resulted in low levels of the physiologically active cytokinin bases as well as their direct riboside precursors in the transgenic lines. Low ACAULIS5 expression and low cytokinin levels of the transgenic trees coincided with low cambial activity of the stem. ACAULIS5 therefore, contrary to its function in young seedlings in Arabidopsis, stimulates cytokinin accumulation and cambial activity during secondary growth of the stem. This function is not derived from maturing secondary xylem tissues as transgenic suppression of ACAULIS5 levels in these tissues did not influence secondary growth. Interestingly, evidence was obtained for increased activity of the anticlinal division of the cambial initials under conditions of low ACAULIS5 expression and low cytokinin accumulation. We propose that ACAULIS5 integrates auxin and cytokinin signaling to promote extensive secondary growth of tree stems.
  •  
32.
  • Milhinhos, Ana, et al. (författare)
  • Thermospermine levels are controlled by an auxin-dependent feedback loop mechanism in Populus xylem
  • 2013
  • Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 75:4, s. 685-698
  • Tidskriftsartikel (refereegranskat)abstract
    • Polyamines are small polycationic amines that are widespread in living organisms. Thermospermine, synthesized by thermospermine synthase ACAULIS5 (ACL5), was recently shown to be an endogenous plant polyamine. Thermospermine is critical for proper vascular development and xylem cell specification, but it is not known how thermospermine homeostasis is controlled in the xylem. We present data in the Populus model system supporting the existence of a negative feedback control of thermospermine levels in stem xylem tissues, the main site of thermospermine biosynthesis. While over-expression of the ACL5 homologue in Populus, POPACAULIS5, resulted in strong up-regulation of ACL5 expression and thermospermine accumulation in leaves, the corresponding levels in the secondary xylem tissues of the stem were similar or lower than those in the wild-type. POPACAULIS5 over-expression had a negative effect on accumulation of indole-3-acetic acid, while exogenous auxin had a positive effect on POPACAULIS5 expression, thus promoting thermospermine accumulation. Further, over-expression of POPACAULIS5 negatively affected expression of the classIII homeodomain leucine zipper (HD-ZipIII) transcription factor gene PttHB8, a homologue of AtHB8, while up-regulation of PttHB8 positively affected POPACAULIS5 expression. These results indicate that excessive accumulation of thermospermine is prevented by a negative feedback control of POPACAULIS5 transcript levels through suppression of indole-3-acetic acid levels, and that PttHB8 is involved in the control of POPACAULIS5 expression. We propose that this negative feedback loop functions to maintain steady-state levels of thermospermine, which is required for proper xylem development, and that it is dependent on the presence of high concentrations of endogenous indole-3-acetic acid, such as those present in the secondary xylem tissues.
  •  
33.
  •  
34.
  • Minina, Alyona, et al. (författare)
  • Metacaspases versus caspases in development and cell fate regulation
  • 2017
  • Ingår i: Cell Death and Differentiation. - : Nature Publishing Group. - 1350-9047 .- 1476-5403. ; 24:8, s. 1314-1325
  • Forskningsöversikt (refereegranskat)abstract
    • Initially found to be critically involved in inflammation and apoptosis, caspases have since then been implicated in the regulation of various signaling pathways in animals. How caspases and caspase-mediated processes evolved is a topic of great interest and hot debate. In fact, caspases are just the tip of the iceberg, representing a relatively small group of mostly animal-specific enzymes within a broad family of structurally related cysteine proteases (family C14 of CD clan) found in all kingdoms of life. Apart from caspases, this family encompasses para-and metacaspases, and all three groups of proteases exhibit significant variation in biochemistry and function in vivo. Notably, metacaspases are present in all eukaryotic lineages with a remarkable absence in animals. Thus, metacaspases and caspases must have adapted to operate under distinct cellular and physiological settings. Here we discuss biochemical properties and biological functions of metacaspases in comparison to caspases, with a major focus on the regulation of developmental aspects in plants versus animals.
  •  
35.
  • Moreau, Charleen, et al. (författare)
  • A genomic approach to investigate developmental cell death in woody tissues of Populus trees
  • 2005
  • Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 6:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Poplar ( Populus sp.) has emerged as the main model system for molecular and genetic studies of forest trees. A Populus expressed sequence tag ( EST) database (POPULUSDB) was previously created from 19 cDNA libraries each originating from different Populus tree tissues, and opened to the public in September 2004. We used this dataset for in silico transcript profiling of a particular process in the woody tissues of the Populus stem: the programmed death of xylem fibers. Results: One EST library in POPULUSDB originates from woody tissues of the Populus stem where xylem fibers undergo cell death. Analysis of EST abundances and library distribution within the POPULUSDB revealed a large number of previously uncharacterized transcripts that were unique in this library and possibly related to the death of xylem fibers. The in silico analysis was complemented by a microarray analysis utilizing a novel Populus cDNA array with a unigene set of 25,000 sequences. Conclusions: In silico analysis, combined with the microarray analysis, revealed the usefulness of non-normalized EST libraries in elucidating transcriptional regulation of previously uncharacterized physiological processes. The data suggested the involvement of two novel extracellular serine proteases, nodulin-like proteins and an Arabidopsis thaliana OPEN STOMATA 1 (AtOST1) homolog in signaling fiber-cell death, as well as mechanisms responsible for hormonal control, nutrient remobilization, regulation of vacuolar integrity and autolysis of the dying fibers.
  •  
36.
  • Muñiz, Luis, et al. (författare)
  • ACAULIS5 controls Arabidopsis xylem specification through the prevention of premature cell death
  • 2008
  • Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 135:15, s. 2573-2582
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell size and secondary cell wall patterning are crucial for the proper functioning of xylem vessel elements in the vascular tissues of plants. Through detailed anatomical characterization of Arabidopsis thaliana hypocotyls, we observed that mutations in the putative spermine biosynthetic gene ACL5 severely affected xylem specification: the xylem vessel elements of the acl5 mutant were small and mainly of the spiral type, and the normally predominant pitted vessels as well as the xylem fibers were completely missing. The cell-specific expression of ACL5 in the early developing vessel elements, as detected by in situ hybridization and reporter gene analyses, suggested that the observed xylem vessel defects were caused directly by the acl5 mutation. Exogenous spermine prolonged xylem element differentiation and stimulated cell expansion and cell wall elaboration in xylogenic cell cultures of Zinnia elegans, suggesting that ACL5 prevents premature death of the developing vessel elements to allow complete expansion and secondary cell wall patterning. This was further supported by our observations that the vessel elements of acl5 seemed to initiate the cell death program too early and that the xylem defects associated with acl5 could be largely phenocopied by induction of premature, diphtheria toxin-mediated cell death in the ACL5-expressing vessel elements. We therefore provide, for the first time, mechanistic evidence for the function of ACL5 in xylem specification through its action on the duration of xylem element differentiation.
  •  
37.
  • Nickolov, Kaloian, et al. (författare)
  • Regulation of PaRBOH1-mediated ROS production in Norway spruce by Ca2+ binding and phosphorylation
  • 2022
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 13
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant respiratory burst oxidase homologs (RBOHs) are plasma membrane-localized NADPH oxidases that generate superoxide anion radicals, which then dismutate to H2O2, into the apoplast using cytoplasmic NADPH as an electron donor. PaRBOH1 is the most highly expressed RBOH gene in developing xylem as well as in a lignin-forming cell culture of Norway spruce (Picea abies L. Karst.). Since no previous information about regulation of gymnosperm RBOHs exist, our aim was to resolve how PaRBOH1 is regulated with a focus on phosphorylation. The N-terminal part of PaRBOH1 was found to contain several putative phosphorylation sites and a four-times repeated motif with similarities to the Botrytis-induced kinase 1 target site in Arabidopsis AtRBOHD. Phosphorylation was indicated for six of the sites in in vitro kinase assays using 15 amino-acid-long peptides for each of the predicted phosphotarget site in the presence of protein extracts of developing xylem. Serine and threonine residues showing positive response in the peptide assays were individually mutated to alanine (kinase-inactive) or to aspartate (phosphomimic), and the wild type PaRBOH1 and the mutated constructs transfected to human kidney embryogenic (HEK293T) cells with a low endogenous level of extracellular ROS production. ROS-producing assays with HEK cells showed that Ca2+ and phosphorylation synergistically activate the enzyme and identified several serine and threonine residues that are likely to be phosphorylated including a novel phosphorylation site not characterized in other plant species. These were further investigated with a phosphoproteomic study. Results of Norway spruce, the first gymnosperm species studied in relation to RBOH regulation, show that regulation of RBOH activity is conserved among seed plants.
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38.
  • Nilsson, Robert, et al. (författare)
  • Metacaspase Substrate Screening using Filter Aided Sample Preparation
  • 2011
  • Ingår i: HUPO-2011: 10th World Congress of the Human Proteome Organization (HUPO): Geneva, Switzerland, September 3rd-7th, 2011: Proceedings-Posters.
  • Konferensbidrag (refereegranskat)abstract
    • Background Metacaspases are proteases essential for programmed cell death (apoptosis) in plants, though most of their substrates remain unknown (1). The activity of metacaspases is a key issue in understanding wood (dead xylem cells) formation in trees. Here, we performed a substrate screening using a recombinant metacaspase that have an expression profile associated with the programmed cell death during wood formation in poplar. Methods Substrate preparation was initiated by total protein extraction from xylem tissue of plants down-regulated (RNA interference) in the expression of the metacaspase gene. Proper conditions intended for screening of the enzyme substrates were achieved by combinations of enzyme and substrate ultrafiltration. Utilizing the low pH activation of the enzyme allowed prompt activation and minute monitoring of newly formed peptides. Peptides were analysed by LC-MSMS using a nano-LC system coupled to a Synapt G2 mass spectrometer. Additional extractions including wild-type plants were performed to support detected substrate processing. Results The results revealed an enzyme active at low temperature (< 7 °C) with properties fitting criteria for cold-adapted enzymes. High specific activity was detected at low temperature and degradation products from the enzyme were formed after 30 min incubation at room temperature. Conclusions Our preliminary data suggest a substrate that has global responses that would clarify the metacaspase involvement in programmed cell death and wood formation. 1.Sundstrom, J. F., Vaculova, A., Smertenko, A. P., Savenkov, E. I., Golovko, A., Minina, E., Tiwari, B. S., Rodriguez-Nieto, S., Zamyatnin, A. A., Valineva, T., Saarikettu, J., Frilander, M. J., Suarez, M. F., Zavialov, A., Stahl, U., Hussey, P. J., Silvennoinen, O., Sundberg, E., Zhivotovsky, B., and Bozhkov, P. V. (2009) Tudor staphylococcal nuclease is an evolutionarily conserved component of the programmed cell death degradome. Nat. Cell Biol. 11, 1347-U198.
  •  
39.
  • Nystedt, Björn, et al. (författare)
  • The Norway spruce genome sequence and conifer genome evolution
  • 2013
  • Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 497:7451, s. 579-584
  • Tidskriftsartikel (refereegranskat)abstract
    • Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinus sylvestris, Abies sibirica, Juniperus communis, Taxus baccata and Gnetum gnemon reveals that the transposable element diversity is shared among extant conifers. Expression of 24-nucleotide small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants. We further identify numerous long (>10,000 base pairs) introns, gene-like fragments, uncharacterized long non-coding RNAs and short RNAs. This opens up new genomic avenues for conifer forestry and breeding.
  •  
40.
  • Obudulu, Ogonna, et al. (författare)
  • A multi-omics approach reveals function of Secretory Carrier-Associated Membrane Proteins in wood formation of​ ​​Populus​​ ​trees
  • 2018
  • Ingår i: BMC Genomics. - : Springer Publishing Company. - 1471-2164. ; 19
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Secretory Carrier-Associated Membrane Proteins (SCAMPs) are highly conserved 32–38 kDa proteins that are involved in membrane trafficking. A systems approach was taken to elucidate function of SCAMPs in wood formation of Populus trees. Phenotypic and multi-omics analyses were performed in woody tissues of transgenic Populus trees carrying an RNAi construct for Populus tremula x tremuloides SCAMP3 (PttSCAMP3;Potri.019G104000).Results: The woody tissues of the transgenic trees displayed increased amounts of both polysaccharides and lignin oligomers, indicating increased deposition of both the carbohydrate and lignin components of the secondary cell walls. This coincided with a tendency towards increased wood density as well as significantly increased thickness of the suberized cork in the transgenic lines. Multivariate OnPLS (orthogonal projections to latent structures) modeling of five different omics datasets (the transcriptome, proteome, GC-MS metabolome, LC-MS metabolome and pyrolysis-GC/MS metabolome) collected from the secondary xylem tissues of the stem revealed systemic variation in the different variables in the transgenic lines, including changes that correlated with the changes in the secondary cell wall composition. The OnPLS model also identified a rather large number of proteins that were more abundant in the transgenic lines than in the wild type. Several of these were related to secretion and/or endocytosis as well as both primary and secondary cell wall biosynthesis.Conclusions: Populus SCAMP proteins were shown to influence accumulation of secondary cell wall components, including polysaccharides and phenolic compounds, in the woody tissues of Populus tree stems. Our multi-omics analyses combined with the OnPLS modelling suggest that this function is mediated by changes in membrane trafficking to fine-tune the abundance of cell wall precursors and/or proteins involved in cell wall biosynthesis and transport. The data provides a multi-level source of information for future studies on the function of the SCAMP proteins in plant stem tissues.
  •  
41.
  • Overmyer, Kirk, et al. (författare)
  • Complex phenotypic profiles leading to ozone sensitivity in Arabidopsis thaliana mutants
  • 2008
  • Ingår i: Plant, Cell and Environment. - : John Wiley & Sons. - 0140-7791 .- 1365-3040. ; 31:9, s. 1237-1249
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetically tractable model plants offer the possibility of defining the plant O3 response at the molecular level. To this end, we have isolated a collection of ozone (O3)‐sensitive mutants of Arabidopsis thaliana. Mutant phenotypes and genetics were characterized. Additionally, parameters associated with O3 sensitivity were analysed, including stomatal conductance, sensitivity to and accumulation of reactive oxygen species, antioxidants, stress gene‐expression and the accumulation of stress hormones. Each mutant has a unique phenotypic profile, with O3 sensitivity caused by a unique set of alterations in these systems. O3 sensitivity in these mutants is not caused by gross deficiencies in the antioxidant pathways tested here. The rcd3 mutant exhibits misregulated stomata. All mutants exhibited changes in stress hormones consistent with the known hormonal roles in defence and cell death regulation. One mutant, dubbed re‐8, is an allele of the classic leaf development mutant reticulata and exhibits phenotypes dependent on light conditions. This study shows that O3 sensitivity can be determined by deficiencies in multiple interacting plant systems and provides genetic evidence linking these systems.
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42.
  • Overmyer, Kirk, et al. (författare)
  • Ozone-induced programmed cell death in the Arabidopsis radical-induced cell death1 mutant.
  • 2005
  • Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 137:3, s. 1092-104
  • Tidskriftsartikel (refereegranskat)abstract
    • Short, high-concentration peaks of the atmospheric pollutant ozone (O3) cause the formation of cell death lesions on the leaves of sensitive plants. Numerous similarities between the plant responses to O3 and pathogens suggest that O3 triggers hypersensitive response-like programmed cell death (PCD). We examined O3 and superoxide-induced cell death in the O3-sensitive radical-induced cell death1 (rcd1) mutant. Dying cells in O3-exposed rcd1 exhibited several of the typical morphological characteristics of the hypersensitive response and PCD. Double-mutant analyses indicated a requirement for salicylic acid and the function of the cyclic nucleotide-gated ion channel AtCNGC2 in cell death. Furthermore, a requirement for ATPases, kinases, transcription, Ca2+ flux, caspase-like proteolytic activity, and also one or more phenylmethylsulfonyl fluoride-sensitive protease activities was shown for the development of cell death lesions in rcd1. Furthermore, mitogen-activated protein kinases showed differential activation patterns in rcd1 and Columbia. Taken together, these results directly demonstrate the induction of PCD by O3.
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43.
  • Pesquet, Edouard, 1975-, et al. (författare)
  • Ethylene stimulates tracheary element differentiation in Zinnia elegans cell cultures
  • 2011
  • Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 190:1, s. 138-149
  • Tidskriftsartikel (refereegranskat)abstract
    • • The exact role of ethylene in xylogenesis remains unclear, but the Zinnia elegans cell culture system provides an excellent model with which to study its role during the differentiation of tracheary elements (TEs) in vitro. • Here, we analysed ethylene homeostasis and function during Z. elegans TE differentiation using biochemical, molecular and pharmacological methods. • Ethylene evolution was confined to specific stages of TE differentiation. It was found to peak at the time of TE maturation and to correlate with the activity of the ethylene biosynthetic 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase. The ethylene precursor ACC was exported and accumulated to high concentrations in the extracellular medium, which also displayed a high capacity to convert ACC into ethylene. The effects of adding inhibitors of the ethylene biosynthetic ACC synthase and ACC oxidase enzymes to the TE cultures demonstrated for the first time strict dependence of TE differentiation on ethylene biosynthesis and a stimulatory effect of ethylene on the rate of TE differentiation. • In a whole-plant context, our results suggest that ethylene synthesis occurs in the apoplast of the xylem elements and that ethylene participates, in a paracrine manner, in the control of the cambial stem cell pool size during secondary xylem formation.
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44.
  • Pesquet, Edouard, et al. (författare)
  • Non-Cell-Autonomous Postmortem Lignification of Tracheary Elements in Zinnia elegans
  • 2013
  • Ingår i: The Plant Cell. - : American Society of Plant Biologists. - 1040-4651 .- 1532-298X. ; 25:4, s. 1314-1328
  • Tidskriftsartikel (refereegranskat)abstract
    • Postmortem lignification of xylem tracheary elements (TEs) has been debated for decades. Here, we provide evidence in Zinnia elegans TE cell cultures, using pharmacological inhibitors and in intact Z. elegans plants using Fourier transform infrared microspectroscopy, that TE lignification occurs postmortem (i.e., after TE programmed cell death). In situ RT-PCR verified expression of the lignin monomer biosynthetic cinnamoyl CoA reductase and cinnamyl alcohol dehydrogenase in not only the lignifying TEs but also in the unlignified non-TE cells of Z. elegans TE cell cultures and in living, parenchymatic xylem cells that surround TEs in stems. These cells were also shown to have the capacity to synthesize and transport lignin monomers and reactive oxygen species to the cell walls of dead TEs. Differential gene expression analysis in Z. elegans TE cell cultures and concomitant functional analysis in Arabidopsis thaliana resulted in identification of several genes that were expressed in the non-TE cells and that affected lignin chemistry on the basis of pyrolysis-gas chromatography/mass spectrometry analysis. These data suggest that living, parenchymatic xylem cells contribute to TE lignification in a non-cellautonomous manner, thus enabling the postmortem lignification of TEs.
  •  
45.
  • Pesquet, Edouard, et al. (författare)
  • Unravelling ethylene biosynthesis and its role during tracheary element formation in Zinnia elegans
  • 2007
  • Ingår i: Advances in plant ethylene research. - Dordrecht : Springer Netherlands. - 9781402060137 - 9781402060144 ; , s. 147-149
  • Konferensbidrag (refereegranskat)abstract
    • Xylem is the plant vascular tissue responsible for raw sap conduction. It comprises two main types of cells that are derived from differentiating cambium: tracheary elements (TEs) and fibres that have conducting and mechanical role, respectively. Xylem formation is a developmental process and is under strict hormonal control involving a stew of phytohormones including auxin, cytokinin and ethylene.
  •  
46.
  • Pitsili, Eugenia, et al. (författare)
  • A phloem-localized Arabidopsis metacaspase (AtMC3) improves drought tolerance
  • 2023
  • Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 239, s. 1281-1299
  • Tidskriftsartikel (refereegranskat)abstract
    • Increasing drought phenomena pose a serious threat to agricultural productivity. Although plants have multiple ways to respond to the complexity of drought stress, the underlying mechanisms of stress sensing and signaling remain unclear. The role of the vasculature, in particular the phloem, in facilitating inter-organ communication is critical and poorly understood. Combining genetic, proteomic and physiological approaches, we investigated the role of AtMC3, a phloem-specific member of the metacaspase family, in osmotic stress responses in Arabidopsis thaliana. Analyses of the proteome in plants with altered AtMC3 levels revealed differential abundance of proteins related to osmotic stress pointing into a role of the protein in water-stress-related responses. Overexpression of AtMC3 conferred drought tolerance by enhancing the differentiation of specific vascular tissues and maintaining higher levels of vascular-mediated transportation, while plants lacking the protein showed an impaired response to drought and inability to respond effectively to the hormone abscisic acid. Overall, our data highlight the importance of AtMC3 and vascular plasticity in fine-tuning early drought responses at the whole plant level without affecting growth or yield.
  •  
47.
  • Renström, Anna, et al. (författare)
  • The effect of nitrogen source and levels on hybrid aspen tree physiology and wood formation
  • 2024
  • Ingår i: Physiologia Plantarum. - : John Wiley & Sons. - 0031-9317 .- 1399-3054. ; 176:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitrogen can be taken up by trees in the form of nitrate, ammonium and amino acids, but the influence of the different forms on tree growth and development is poorly understood in angiosperm species like Populus. We studied the effects of both organic and inorganic forms of nitrogen on growth and wood formation of hybrid aspen trees in experimental conditions that allowed growth under four distinct steady-state nitrogen levels. Increased nitrogen availability had a positive influence on biomass accumulation and the radial dimensions of both xylem vessels and fibers, and a negative influence on wood density. An optimal level of nitrogen availability was identified where increases in biomass accumulation outweighed decreases in wood density. None of these responses depended on the source of nitrogen except for shoot biomass accumulation, which was stimulated more by treatments complemented with nitrate than by ammonium alone or the organic source arginine. The most striking difference between the nitrogen sources was the effect on lignin composition, whereby the abundance of H-type lignin increased only in the presence of nitrate. The differential effect of nitrate is possibly related to the well-known role of nitrate as a signaling compound. RNA-sequencing revealed that while the lignin-biosynthetic genes did not significantly (FDR <0.01) respond to added NO3- , the expression of several laccases, catalysing lignin polymerization, was dependent on N-availability. These results reveal a unique role of nitrate in wood formation and contribute to the knowledge basis for decision-making in utilizing hybrid aspen as a bioresource.
  •  
48.
  • Serk, Henrik, 1980-, et al. (författare)
  • Cooperative lignification of xylem tracheary elements
  • 2015
  • Ingår i: Plant Signalling & Behavior. - : Taylor & Francis Group. - 1559-2316 .- 1559-2324. ; 10:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of xylem tracheary elements (TEs) – the hydro-mineral sap conducting cells - has been an evolutionary breakthrough to enable long distance nutrition and upright growth of vascular land plants. To allow sap conduction, TEs form hollow laterally reinforced cylinders by combining programmed cell death and secondary cell wall formation. To ensure their structural resistance for sap conduction, TE cell walls are reinforced with the phenolic polymer lignin, which is deposited after TE cell death by the cooperative supply of monomers and other substrates from the surrounding living cells.
  •  
49.
  • Seyfferth, Carolin, et al. (författare)
  • Ethylene-Related Gene Expression Networks in Wood Formation
  • 2018
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • Thickening of tree stems is the result of secondary growth, accomplished by the meristematic activity of the vascular cambium. Secondary growth of the stem entails developmental cascades resulting in the formation of secondary phloem outwards and secondary xylem (i.e., wood) inwards of the stem. Signaling and transcriptional reprogramming by the phytohormone ethylene modifies cambial growth and cell differentiation, but the molecular link between ethylene and secondary growth remains unknown. We addressed this shortcoming by analyzing expression profiles and co-expression networks of ethylene pathway genes using the AspWood transcriptome database which covers all stages of secondary growth in aspen (Populus tremula) stems. ACC synthase expression suggests that the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is synthesized during xylem expansion and xylem cell maturation. Ethylene-mediated transcriptional reprogramming occurs during all stages of secondary growth, as deduced from AspWood expression profiles of ethylene-responsive genes. A network centrality analysis of the AspWood dataset identified EIN3D and 11 ERFs as hubs. No overlap was found between the co-expressed genes of the EIN3 and ERF hubs, suggesting target diversification and hence independent roles for these transcription factor families during normal wood formation. The EIN3D hub was part of a large co-expression gene module, which contained 16 transcription factors, among them several new candidates that have not been earlier connected to wood formation and a VND-INTERACTING 2 (VNI2) homolog. We experimentally demonstrated Populus EIN3D function in ethylene signaling in Arabidopsis thaliana. The ERF hubs ERF118 and ERF119 were connected on the basis of their expression pattern and gene co-expression module composition to xylem cell expansion and secondary cell wall formation, respectively. We hereby establish data resources for ethylene-responsive genes and potential targets for EIN3D and ERF transcription factors in Populus stem tissues, which can help to understand the range of ethylene targeted biological processes during secondary growth.
  •  
50.
  • Seyfferth, Carolin, et al. (författare)
  • Ethylene Signaling Is Required for Fully Functional Tension Wood in Hybrid Aspen
  • 2019
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Tension wood (TW) in hybrid aspen trees forms on the upper side of displaced stems to generate a strain that leads to uplifting of the stem. TW is characterized by increased cambial growth, reduced vessel frequency and diameter, and the presence of gelatinous, cellulose-rich (G-)fibers with its microfibrils oriented parallel to the fiber cell axis. Knowledge remains limited about the molecular regulators required for the development of this special xylem tissue with its characteristic morphological, anatomical, and chemical features. In this study, we use transgenic, ethylene-insensitive (ETI) hybrid aspen trees together with time-lapse imaging to show that functional ethylene signaling is required for full uplifting of inclined stems. X-ray diffraction and Raman microspectroscopy of TW in ETI trees indicate that, although G-fibers form, the cellulose microfibril angle in the G-fiber S-layer is decreased, and the chemical composition of S- and G-layers is altered than in wild-type TW. The characteristic asymmetric growth and reduction of vessel density is suppressed during TW formation in ETI trees. A genome-wide transcriptome profiling reveals ethylene-dependent genes in TW, related to cell division, cell wall composition, vessel differentiation, microtubule orientation, and hormone crosstalk. Our results demonstrate that ethylene regulates transcriptional responses related to the amount of G-fiber formation and their properties (chemistry and cellulose microfibril angle) during TW formation. The quantitative and qualitative changes in G-fibers are likely to contribute to uplifting of stems that are displaced from their original position.
  •  
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