| 1. |
- Alexandersson, Erik, et al.
(författare)
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Transcriptional regulation of aquaporins in accessions of Arabidopsis in response to drought stress.
- 2010
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Ingår i: Plant Journal. - 1365-313X. ; 61, s. 650-660
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Tidskriftsartikel (refereegranskat)abstract
- Summary Aquaporins facilitate water transport over cellular membranes and are therefore believed to play an important role in water homeostasis. In higher plants aquaporin-like proteins, also called major intrinsic proteins (MIPs), are divided into 5 subfamilies. We have previously shown that MIP transcription in Arabidopsis thaliana generally is down-regulated in leaves upon drought stress, apart from two members of the Plasma membrane Intrinsic Protein (PIP) subfamily, AtPIP1;4 and AtPIP2;5, which are up-regulated. In order to assess if this regulation is general or accession-specific we monitored gene expression of all PIPs in five Arabidopsis accessions. Overall drought regulation of PIPs was well conserved for all five accessions tested suggesting a general and fundamental physiological role of this drought response. In addition, significant differences among accessions were identified for transcripts of three PIP genes. Principal component analysis showed that most of the PIP transcriptional variation during drought stress could be explained by one variable linked to leaf water content. Promoter-GUS constructs of AtPIP1;4, AtPIP2;5 and also AtPIP2;6, which is unresponsive to drought stress, had distinct expression patterns concentrated to the base of the leaf petioles and parts of the flowers. The presence of drought stress response elements within the 1.6 kb promoter regions of AtPIP1;4 and AtPIP2;5, was demonstrated by comparing transcription of the promoter reporter construct and the endogenous gene upon drought stress. Analysis by ATTED-II and other web-based bioinformatical tools showed that several of the MIPs down-regulated upon drought are strongly co-expressed, whereas AtPIP1;4, AtPIP2;5 and AtPIP2;6 are not co-expressed.
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| 2. |
- Carlsbecker, Annelie, et al.
(författare)
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The MADS-box gene DAL1 is a potential mediator of the juvenile-to-adult transition in Norway spruce (Picea abies)
- 2004
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Ingår i: The Plant Journal. ; 40:4, s. 546-557
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Tidskriftsartikel (refereegranskat)abstract
- Progression through the plant life cycle involves changes in many essential features, most notably in the capacity to reproduce. The transition from juvenile vegetative and non-reproductive to an adult reproductive phase is gradual and can take many years; in the conifer Norway spruce, Picea abiea, typically 20-25 years. We present a detailed analysis of the activities of three regulatory genes with potential roles in the transition in Norway spruce: DAL1, a MADS-box gene related to the AGL6 group of genes from angiosperms, and the two LEAFY-related genes PaLFY and PaNLY. DAL1 activity is initiated in the shoots of juvenile trees at an age of 3-5 years, and then increases with age, whereas both LFY genes are active throughout the juvenile phase. The activity of DAL1 further shows a spatial pattern along the stem of the tree that parallels a similar gradient in physiolpoical and morphological features associated with maturation to the adult phase. Constitutive expression of DAL1 in transgenic Arabidopsis plants caused a dramatic attenuation of both juvenile and adult growth phases;flowers forming immediately after the embryogenic phase of development in severely affected plants. Taken together, our resulsts support the notion that DAL1 may have a regulatory role in the juvenile-to-adult transition in Norway spruce.
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| 3. |
- Escobar, Matthew, et al.
(författare)
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Reorganization of the alternative pathways of the Arabidopsis respiratory chain by nitrogen supply: opposing effects of ammonium and nitrate
- 2006
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Ingår i: Plant Journal. - 1365-313X. ; 45:5, s. 775-788
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial oxidative phosphorylation system in plants possesses a variety of alternative pathways that decrease respiratory ATP production. These alternative pathways are mediated by three classes of bypass proteins: the type II NAD(P) H dehydrogenases (which circumvent complex I of the electron transport chain), the alternative oxidases (AOXs; which circumvent complexes III and IV) and the uncoupling proteins ( which circumvent ATP synthase). We have monitored the expression of all genes encoding respiratory bypass proteins in Arabidopsis thaliana growing with different sources of inorganic nitrogen (N). Resupply of nitrate (NO3-) to N-limited seedling cultures caused a decrease in the transcript abundance of several type II NAD(P) H dehydrogenase and AOX genes, while resupply of ammonium (NH4+) led to broad increases in expression in the same gene families. Similar results were observed upon switching between nitrate and ammonium in the absence of N stress. Nitrate signalling was found to be mediated primarily by the nitrate ion itself, whereas ammonium regulation was dependent upon assimilation and affected by changes in apoplastic pH. Corresponding alterations in alternative respiratory pathway capacities were apparent in seedlings supplied with either nitrate or ammonium as an N source and in mitochondria purified from the seedlings. Specifically, AOX capacity and protein abundance, as well as calcium-dependent external NADH oxidation, were substantially elevated after growth on ammonium. The increased capacity of respiratory bypass pathways after switching from nitrate to ammonium was correlated to an overall respiratory increase.
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| 4. |
- Gustavsson, Niklas, et al.
(författare)
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A peptide methionine sulfoxide reductase highly expressed in photosynthetic tissue in Arabidopsis thaliana can protect the chaperone-like activity of a chloroplast-localized small heat shock protein.
- 2002
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Ingår i: Plant Journal. - 1365-313X. ; 29:5, s. 545-553
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of methionine residues in proteins to methionine sulfoxides occurs frequently and protein repair by reduction of the methionine sulfoxides is mediated by an enzyme, peptide methionine sulfoxide reductase (PMSR, EC 1.8.4.6), universally present in the genomes of all so far sequenced organisms. Recently, five PMSR-like genes were identified in Arabidopsis thaliana, including one plastidic isoform, chloroplast localised plastidial peptide methionine sulfoxide reductase (pPMSR) that was chloroplast-localized and highly expressed in actively photosynthesizing tissue (Sadanandom A et al., 2000). However, no endogenous substrate to the pPMSR was identified. Here we report that a set of highly conserved methionine residues in Hsp21, a chloroplast-localized small heat shock protein, can become sulfoxidized and thereafter reduced back to methionines by this pPMSR. The pPMSR activity was evaluated using recombinantly expressed pPMSR and Hsp21 from Arabidopsis thaliana and a direct detection of methionine sulfoxides in Hsp21 by mass spectrometry. The pPMSR-catalyzed reduction of Hsp21 methionine sulfoxides occurred on a minute time-scale, was ultimately DTT-dependent and led to recovery of Hsp21 conformation and chaperone-like activity, both of which are lost upon methionine sulfoxidation (Härndahl et al., 2001). These data indicate that one important function of pPMSR may be to prevent inactivation of Hsp21 by methionine sulfoxidation, since small heat shock proteins are crucial for cellular resistance to oxidative stress.
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| 5. |
- Hunt, L, et al.
(författare)
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Phospholipase C is required for the control of stomatal aperture by ABA
- 2003
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Ingår i: Plant Journal. - 1365-313X. ; 34:1, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- The calcium-releasing second messenger inositol 1,4,5-trisphosphate is involved in the regulation of stomatal aperture by ABA. In other signalling pathways, inositol 1,4,5-trisphosphate is generated by the action of phospholipase C. We have studied the importance of phospholipase C in guard cell ABA-signalling pathways. Immunolocalisation of a calcium-activated phospholipase C confirmed the presence of phospholipase C in tobacco guard cells. Transgenic tobacco plants with considerably reduced levels of phospholipase C in their guard cells were only partially able to regulate their stomatal apertures in response to ABA. These results suggest that phospholipase C is involved in the amplification of the calcium signal responsible for reductions in stomatal aperture in response to ABA. As full ABA-induced inhibition of stomatal opening was not observed, our results support a role for the action of other calcium-releasing second messengers in the guard cell ABA-signalling pathway. It is not known whether these different calcium-releasing second messengers act in the same or parallel ABA-signalling pathways.
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| 6. |
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| 7. |
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| 8. |
- Michalecka, Agnieszka, et al.
(författare)
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Identification of a mitochondrial external NADPH dehydrogenase by overexpression in transgenic Nicotiana sylvestris
- 2004
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Ingår i: Plant Journal. - 1365-313X. ; 37:3, s. 415-425
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Tidskriftsartikel (refereegranskat)abstract
- The plant respiratory chain contains a complex setup of non-energy conserving NAD(P)H dehydrogenases, the physiological consequences of which are highly unclear. An expression construct for the potato (Solanum tuberosum L., cv. Desiree) ndb1 gene, a homologue of bacterial and fungal type II NAD(P)H dehydrogenases, was introduced into Nicotiana sylvestris. Transgenic lines with high transcript and protein levels for St-NDB1 had up to threefold increased activity of external NADPH dehydrogenase in isolated mitochondria as compared to the wild type (WT). In two lines, the external NADPH dehydrogenase activity was instead 10-fold decreased, indicating that the corresponding N. sylvestris gene had been suppressed. Activities of external and internal rotenone-insensitive NADH dehydrogenases were unchanged in the transgenic lines. The results demonstrate that the St-ndb1 encodes an external dehydrogenase specific for NADPH and dependent on calcium for activity. Transgenic lines overexpressing St-ndb1 had specifically increased protein levels for alternative oxidase and uncoupling protein, as compared to the WT and one co-suppressing line. This indicates cross-talk in the expressional control, or metabolic conditions influencing it, for the different categories of energy-dissipating proteins that bypass oxidative phosphorylation. The potential effects of external NADPH oxidation on other cellular processes are discussed.
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| 9. |
- Saavedra, Laura, et al.
(författare)
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PIPKs are essential for rhizoid elongation and caulonemal cell development in the moss Physcomitrella patens
- 2011
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 67:4, s. 635-647
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Tidskriftsartikel (refereegranskat)abstract
- PtdIns-4,5-bisphosphate is a lipid messenger of eukaryotic cells that plays a critical role in processes such as cytoskeleton organization, intracellular vesicular trafficking, secretion, cell motility, regulation of ion channels and nuclear signalling pathways. The enzymes responsible for the synthesis of PtdIns(4,5)P(2) are phosphatidylinositol phosphate kinases (PIPKs). The moss Physcomitrella patens contains two PIPKs, PpPIPK1 and PpPIPK2. To study their physiological role, both genes were disrupted by targeted homologous recombination and as a result mutant plants with lower PtdIns(4,5)P(2) levels were obtained. A strong phenotype for pipk1, but not for pipk2 single knockout lines, was obtained. The pipk1 knockout lines were impaired in rhizoid and caulonemal cell elongation, whereas pipk1-2 double knockout lines showed dramatic defects in protonemal and gametophore morphology manifested by the absence of rapidly elongating caulonemal cells in the protonemal tissue, leafy gametophores with very short rhizoids, and loss of sporophyte production. pipk1 complemented by overexpression of PpPIPK1 fully restored the wild-type phenotype whereas overexpression of the inactive PpPIPK1E885A did not. Overexpression of PpPIPK2 in the pipk1-2 double knockout did not restore the wild-type phenotype demonstrating that PpPIPK1 and PpPIPK2 are not functionally redundant. In vivo imaging of the cytoskeleton network revealed that the shortened caulonemal cells in the pipk1 mutants was the result of the absence of the apicobasal gradient of cortical F-actin cables normally observed in wild-type caulonemal cells. Our data indicate that both PpPIPKs play a crucial role in the development of the moss P. patens, and particularly in the regulation of tip growth.
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| 10. |
- Schussler, Manuela Desiree, et al.
(författare)
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The effects of the loss of TIP1;1 and TIP1;2 aquaporins in Arabidopsis thaliana
- 2008
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Ingår i: Plant Journal. - 1365-313X. ; 56:5, s. 756-767
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Tidskriftsartikel (refereegranskat)abstract
- Loss of aquaporin TIP1;1 in Arabidopsis has been suggested to result in early senescence and plant death. This was based on the fact that a partial reduction of TIP1;1 by RNA interference (RNAi) led to gradual phenotypes, ranging from indistinguishable from wild type to lethality, depending on the degree of downregulation of the target messenger, and displaying pleiotropic effects in primary metabolism and cell signalling. A hypothesis was put forward to suggest that TIP1;1, apart from its transport function, may play an essential role in vesicle routing. Here we identify an Arabidopsis transposon insertion line tip1;1-1 that is completely devoid of TIP1;1 protein, as demonstrated by western blotting and immunolocalization using an isoform-specific antibody. Strikingly, the complete absence of the protein did not result in any significant effect on metabolism or elemental composition of the plants. Microarray analysis did not indicate increased expression of other aquaporins to compensate for the lack of TIP1;1 in tip1;1-1. We further developed a double mutant of TIPs in Arabidopsis, lacking both TIP1;1 and its closest paralog TIP1;2. Arabidopsis mutants lacking both TIP1;1 and TIP1;2 showed a minor increase in anthocyanin content, and a reduction in catalase activity, but showed no changes in water status. In contrast to earlier reports, plants lacking TIP1;1 and TIP1;2 aquaporins are alive and thriving. We suggest that RNAi directed towards TIP1;1 may have resulted in off-target gene silencing, a notion that is potentially interesting for various studies analysing gene function by RNAi.
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| 11. |
- Sjodin, Andreas, et al.
(författare)
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UPSC-BASE - Populus transcriptomics online
- 2006
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Ingår i: The Plant Journal. - Oxford : Blackwell. - 0960-7412 .- 1365-313X. ; 48:5, s. 806-817
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Tidskriftsartikel (refereegranskat)abstract
- The increasing accessibility and use of microarrays in transcriptomics has accentuated the need for purpose-designed storage and analysis tools. Here we present UPSC-BASE, a database for analysis and storage of Populus DNA microarray data. A microarray analysis pipeline has also been established to allow consistent and efficient analysis (from small to large scale) of samples in various experimental designs. A range of optimized experimental protocols is provided for each step in generating the data. Within UPSC-BASE, researchers can perform standard and advanced microarray analysis procedures in a user-friendly environment. Background corrections, normalizations, quality-control tools, visualizations, hypothesis tests and export tools are provided without requirements for expert-level knowledge. Although the database has been developed primarily for handling Populus DNA microarrays, most of the tools are generic and can be used for other types of microarray. UPSC-BASE is also a repository of Populus microarray information, providing data from 21 experiments on a total of 407 microarray hybridizations in the public domain of the database. There are also an additional 10 experiments containing 347 hybridizations, where the automatically analysed data are searchable.
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| 12. |
- Stöhr, Christine, et al.
(författare)
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An agarose gel electrophoresis method for the separation of arabinogalactan proteins.
- 1996
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Ingår i: Plant Journal. - 1365-313X. ; 10:5, s. 943-948
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Tidskriftsartikel (refereegranskat)abstract
- A method for resolving plasma membrane associated arabinogalactan proteins (AGPs) has been developed. Plasma membranes purified by aqueous polymer two‐phase partitioning were first subjected to Triton X‐114 fractionation. The resulting water phase contained all detectable plasma membrane‐bound AGPs. Plasma membrane AGPs were then resolved in an SDS‐agarose gel electrophoresis system (SDS‐AGE). For separating plasma membrane AGP species of the same apparent molecular weight but with different net charge, a two‐dimensional electrophoresis system was used, utilizing isoelectric focusing in an immobilized pH gradient in the first dimension and SDS‐AGE in the second dimension. These methods enabled the separation of individual plasma membrane AGPs. In comparison, SDS‐PAGE methods left AGPs as unresolved high molecular‐weight smears. The methods described here may help to establish some basic features of AGPs, such as the number, organization, and protein and carbohydrate characteristics of plasma membrane AGPs, as well as the relationship between plasma membrane and extracellular AGPs.
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| 13. |
- Svensson, Staffan, et al.
(författare)
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Light-dependent gene expression for proteins in the respiratory chain of potato mitochondria
- 2001
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Ingår i: Plant Journal. - 1365-313X. ; 28:1, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- Expression of genes for respiratory chain dehydrogenases was investigated in potato (Solanum tuberosum L. cv. Desiree) leaves. The recently characterized nda1 and ndb1 genes, homologues to genes encoding the non-proton pumping respiratory chain NADH-dehydrogenases of Escherichia coli and yeast, were compared to genes encoding catalytic subunits of the proton-pumping NADH dehydrogenase (complex I). As leaves develop from young to mature, the nda1 transcript level increases, accompanied by an elevation in immunodetected NDA protein and internal rotenone-insensitive NADH oxidation. The other investigated transcripts, proteins and NAD(P)H oxidation activities were essentially unchanged. A variation in transcript level, specific for nda1, is seen at different times of the day with highest expression in the morning. This variation also influences the apparent developmental induction. Further, the nda1 mRNA in leaves specifically and completely disappears during dark treatment, with a rapid re-induction when plants are returned to light. Corresponding immunodetected NDA protein is specifically decreased in mitochondria isolated from dark-treated plants, accompanied by a lower capacity for internal rotenone-insensitive NADH oxidation. Complete light dependence and diurnal changes in expression have previously not been reported for genes encoding respiratory chain proteins. Qualitatively similar to NDA, the alternative oxidase showed developmental induction and light dependence. In addition to the specific change in nda1, a general, slower down-regulation in darkness was seen for the other NAD(P)H dehydrogenase genes. The nda1 expression during development, and in response to light, indicates a specific role of the encoded enzyme in the photosynthetically associated mitochondrial metabolism.
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| 14. |
- Engdahl, Sheila, et al.
(författare)
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Association of the NADPH : protochlorophyllide oxidoreductase (POR) with isolated etioplast inner membranes from wheat
- 2001
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Ingår i: The Plant Journal. - Oxford : Blackwell. - 0960-7412 .- 1365-313X. ; 27:4, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- Membrane association of NADPH:protochlorophyllide oxidoreductase (POR, EC: 1.6.99.1) with isolated prolamellar bodies (PLBs) and prothylakoids (PTs) from wheat etioplasts was investigated. in vitro-expressed radiolabelled POR, with or without transit peptide, was used to characterize membrane association conditions. Proper association of POR with PLBs and PTs did not require the presequence, whereas NADPH and hydrolysable ATP were vital for the process. After treating the membranes with thermolysin, sodium hydroxide or carbonate, a firm attachment of the POR protein to the membrane was found. Although the PLBs and PTs differ significantly in their relative amount of POR in vivo, no major differences in POR association capacity could be observed between the two membrane systems when exogenous NADPH was added, Experiments run with only an endogenous NADPH source almost abolished association of POR with both PLBs and PTs. In addition, POR protein carrying a mutation in the putative nucleotide-binding site (ALA06) was unable to bind to the inner membranes in the presence of NADPH, which further demonstrates that the co-factor is essential for proper membrane association. POR protein carrying a mutation in the substrate-binding site (ALA24) showed less binding to the membranes as compared to the wild type. The results presented here introduce studies of a novel area of protein-membrane interaction, namely the association of proteins with a paracrystalline membrane structure, the PLB.
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| 15. |
- Hertzberg, Magnus, et al.
(författare)
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cDNA microarray analysis of small tissue samples using a cDNA tag target amplification protocol
- 2001
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 25:5, s. 585-591
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Tidskriftsartikel (refereegranskat)abstract
- Microarray technology is becoming an important comprehensive tool to study gene expression in plants. However, the use of this technology is limited by the large amount of sample tissue needed for microarray analysis. Generally, 50-200 mug of total RNA and 1-2 mug of mRNA is required for each hybridisation, which is equivalent to 50-100 mg of plant tissue. This requirement for large amounts of starting material severely constrains the use of microarrays for transcript profiling in specific tissues and cell types during plant development. Here we report on a robust and reliable target amplification method that enables transcript profiling from sub-mg amounts of plant tissue. Using 0.1 mug of total RNA we show that twofold expression differences are possible to distinguish with 99% confidence. We also demonstrate the application of this method in an analysis of secondary phloem development in hybrid aspen using defined tissue sections, corresponding to 2-4 cell layers with a fresh weight of similar to 0.5 mg.
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| 16. |
- Reidt, W., et al.
(författare)
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Gene regulation during late embryogenesis : the RY motif of maturation-specific gene promoters is a direct target of the FUS3 gene product
- 2000
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 21:5, s. 401-408
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Tidskriftsartikel (refereegranskat)abstract
- The Arabidopsis mutants fus3 and abi3 show pleiotropic effects during embryogenesis including reduced levels of transcripts encoding embryo-specific seed proteins. To investigate the interaction between the BO-domain-containing transcription factors FUSS and ABI3 with the RY cis-motif, conserved in many seed-specific promoters, a promoter analysis as well as band-shift experiments were performed. The analysis of promoter mutants revealed the structural requirements for the function of the RY cis-element. It is shown that both the nucleotide sequence and the alternation of purin and pyrimidin nucleotides (RY character) are essential for the activity of the motif. Further, it was shown that FUSS and ABI3 can act independently of each other in controlling promoter activity and that the RY cis-motif is a target for both transcription factors. For FUSS, which is so far the smallest known member of the B3-domain family, a physical interaction with the RY motif was established. The functional and biochemical data demonstrate that the regulators FUSS and ABI3 are essential components of a regulatory network acting in concert through the RY-promoter element to control gene expression during late embryogenesis and seed development.
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| 17. |
- Kindgren, Peter, et al.
(författare)
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The plastid redox insensitive 2 mutant of Arabidopsis is impaired in PEP activity and high light-dependent plastid redox signalling to the nucleus
- 2012
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 70:2, s. 279-291
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Tidskriftsartikel (refereegranskat)abstract
- The photosynthetic apparatus is composed of proteins encoded by genes from both the nuclear and the chloroplastic genomes. The activities of the nuclear and chloroplast genomes must therefore be closely coordinated through intracellular signalling. The plastids produce multiple retrograde signals at different times of their development, and in response to changes in the environment. These signals regulate the expression of nuclear-encoded photosynthesis genes to match the current status of the plastids. Using forward genetics we identified PLASTID REDOX INSENSITIVE 2 (PRIN2), a chloroplast component involved in redox-mediated retrograde signalling. The allelic mutants prin2-1 and prin2-2 demonstrated a misregulation of photosynthesis-associated nuclear gene expression in response to excess light, and an inhibition of photosynthetic electron transport. As a consequence of the misregulation of LHCB1.1 and LHCB2.4, the prin2 mutants displayed a high irradiance-sensitive phenotype with significant photoinactivation of photosystem II, indicated by a reduced variable to maximal fluorescence ratio (Fv/Fm). PRIN2 is localized to the nucleoids, and plastid transcriptome analyses demonstrated that PRIN2 is required for full expression of genes transcribed by the plastid-encoded RNA polymerase (PEP). Similarly to the prin2 mutants, the ys1 mutant with impaired PEP activity also demonstrated a misregulation of LHCB1.1 and LHCB2.4 expression in response to excess light, suggesting a direct role for PEP activity in redox-mediated retrograde signalling. Taken together, our results indicate that PRIN2 is part of the PEP machinery, and that the PEP complex responds to photosynthetic electron transport and generates a retrograde signal, enabling the plant to synchronize the expression of photosynthetic genes from both the nuclear and plastidic genomes.
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| 18. |
- Andersson-Gunneras, S., et al.
(författare)
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Biosynthesis of cellulose-enriched tension wood in Populus : global analysis of transcripts and metabolites identifies biochemical and developmental regulators in secondary wall biosynthesis
- 2006
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Ingår i: The Plant Journal. - Malden : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 45:2, s. 144-165
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Tidskriftsartikel (refereegranskat)abstract
- Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) x tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon
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| 19. |
- Andersson-Gunnerås, Sara, et al.
(författare)
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Asymmetric expression of a poplar ACC oxidase controls ethylene production during gravitational induction of tension wood
- 2003
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Ingår i: The Plant Journal. - : Blackwell Publishing. - 0960-7412 .- 1365-313X. ; 34:3, s. 339-349
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Tidskriftsartikel (refereegranskat)abstract
- Ethylene is produced in wood-forming tissues, and when applied exogenously, it has been shown to cause profound effects on the pattern and rate of wood development. However, the molecular regulation of ethylene biosynthesis during wood formation is poorly understood. We have characterised an abundant 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene (PttACO1) in the wood-forming tissues of Populus tremula (L.) × P. tremuloides (Michx). PttACO1 is primarily expressed in developing secondary xylem, and is specifically upregulated during secondary wall formation. Nevertheless, according to GC–MS analysis combined with tangential cryosectioning, the distribution of ACC was found to be fairly uniform across the cambial-region tissues. Gravitational stimulation, which causes tension wood to form on the upper side of the stem, resulted in a strong induction of PttACO1 expression and ACC oxidase activity in the tension wood-forming tissues. The ACC levels increased in parallel to the PttACO1 expression. However, the increase on the upper (tension wood) side was only minor, whereas large amounts of both ACC and its hydrolysable conjugates accumulated on the lower (opposite) side of the stem. This suggests that the relatively low level of ACC on the tension wood side is a result of its conversion to ethylene by the highly upregulated PttACO1, and the concurrent accumulation of ACC on the opposite side of the wood is because of the low PttACO1 levels. We conclude that PttACO1 and ACC oxidase activity, but not ACC availability, are important in the control of the asymmetric ethylene production within the poplar stem when tension wood is induced by gravitational stimulation.
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| 20. |
- Andersson, Jenny, et al.
(författare)
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Absence of the Lhcb1 and Lhcb2 proteins of the light-harvesting complex of photosystem II - effects on photosynthesis, grana stacking and fitness
- 2003
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 35:3, s. 350-361
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed Arabidopsis thaliana plants that are virtually devoid of the major light-harvesting complex, LHC II. This was accomplished by introducing the Lhcb2.1 coding region in the antisense orientation into the genome by Agrobacterium-mediated transformation. Lhcb1 and Lhcb2 were absent, while Lhcb3, a protein present in LHC II associated with photosystem (PS) II, was retained. Plants had a pale green appearance and showed reduced chlorophyll content and an elevated chlorophyll a/b ratio. The content of PS II reaction centres was unchanged on a leaf area basis, but there was evidence for increases in the relative levels of other light harvesting proteins, notably CP26, associated with PS II, and Lhca4, associated with PS I. Electron microscopy showed the presence of grana. Photosynthetic rates at saturating irradiance were the same in wild-type and antisense plants, but there was a 10-15% reduction in quantum yield that reflected the decrease in light absorption by the leaf. The antisense plants were not able to perform state transitions, and their capacity for non-photochemical quenching was reduced. There was no difference in growth between wild-type and antisense plants under controlled climate conditions, but the antisense plants performed worse compared to the wild type in the field, with decreases in seed production of up to 70%.
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| 21. |
- Bellec, Y., et al.
(författare)
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Pasticcino2 is a protein tyrosine phosphatase-like involved in cell proliferation and differentiation in Arabidopsis
- 2002
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Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 32:5, s. 713-722
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Tidskriftsartikel (refereegranskat)abstract
- The pasticcino2 (pas2) mutant shows impaired embryo and seedling development associated with cell dedifferentiation and proliferation. This process is specifically enhanced in presence of cytokinins leading to callus-like structure of the apical part of the seedling. Cell proliferation concerns localized and stochastic nodules of dividing cells. In absence of cytokinins, cell proliferation leads to small calli on stems but, most often, cell proliferation is associated with post-genital organ fusion. The PAS2 gene was identified by positional cloning. PAS2 expression was found in every plant organ and was not regulated by PAS1 and PAS3 genes. PAS2 encodes the Arabidopsis member of the protein tyrosine phosphatase-like (Ptpl) family, a new PTP family originally described in mice and humans and characterized by a mutated PTP active site. This family of proteins has a yeast homolog that is essential for cell viability. The absence of yeast PAS2 homolog can be functionally replaced by the Arabidopsis PAS2 protein, demonstrating that PAS2 function is conserved between higher and lower eukaryotes.
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| 22. |
- Benlloch, Reyes, et al.
(författare)
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Integrating long-day flowering signals : a LEAFY binding site is essential for proper photoperiodic activation of APETALA1
- 2011
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Ingår i: The Plant Journal. - Oxford : Blackwell. - 0960-7412 .- 1365-313X. ; 67:6, s. 1094-1102
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Tidskriftsartikel (refereegranskat)abstract
- The transition to flowering in Arabidopsis is characterized by the sharp and localized upregulation of APETALA1 (AP1) transcription in the newly formed floral primordia. Both the flower meristem-identity gene LEAFY (LFY) and the photoperiod pathway involving the FLOWERING LOCUS T (FT) and FD genes contribute to this upregulation. These pathways have been proposed to act independently but their respective contributions and mode of interaction have remained elusive. To address these questions, we studied the AP1 regulatory region. Combining in vitro and in vivo approaches, we identified which of the three putative LFY binding sites present in the AP1 promoter is essential for its activation by LFY. Interestingly, we found that this site is also important for the correct photoperiodic-dependent upregulation of AP1. In contrast, a previously proposed putative FD-binding site appears dispensable and unable to bind FD and we found no evidence for FD binding to other sites in the AP1 promoter, suggesting that the FT/FD-dependent activation of AP1 might be indirect. Altogether, our data give new insight into the interaction between the FT and LFY pathways in the upregulation of AP1 transcription under long-day conditions.
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| 23. |
- Björklund, Simon, et al.
(författare)
-
Cross-talk between gibberellin and auxin in development of Populus wood: gibberellin stimulates polar auxin transport and has a common transcriptome with auxin
- 2007
-
Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 52:3, s. 499-511
-
Tidskriftsartikel (refereegranskat)abstract
- Both indole acetic acid (IAA) and gibberellins (GAs) stimulate cell and organ growth. We have examined GA/IAA cross-talk in cambial growth of hybrid aspen (Populus tremulaxtremuloides). Decapitated trees were fed with IAA and GA, alone and in combination. Endogenous hormone levels after feeding were measured, by mass spectrometry, in the stem tissues below the point of application. These stem tissues with defined hormone balances were also used for global transcriptome analysis, and the abundance of selected transcripts was measured by real-time reverse-transcription polymerase chain reaction. By feeding isotope-labeled IAA, we demonstrated that GA increases auxin levels in the stem by stimulating polar auxin transport. This finding adds a new dimension to the concept that the endogenous GA/IAA balance in plants is determined by cross-talk between the two hormones. We also show that GA has a common transcriptome with auxin, including many transcripts related to cell growth. This finding provides molecular support to physiological experiments demonstrating that either hormone can induce growth if the other hormone is absent/deficient because of mutations or experimental treatments. It also highlights the potential for extensive cross-talk between GA- and auxin-induced responses in vegetative growth of the intact plant. The role of endogenous IAA and GA in wood development is discussed.
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| 24. |
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| 25. |
- Bylesjö, Max, et al.
(författare)
-
Data integration in plant biology the O2PLS method for combined modeling of transcript and metabolite data
- 2007
-
Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 52:6, s. 1181-1191
-
Tidskriftsartikel (refereegranskat)abstract
- The technological advances in the instrumentation employed in life sciences have enabled the collection of a virtually unlimited quantity of data from multiple sources. By gathering data from several analytical platforms, with the aim of parallel monitoring of, e.g. transcriptomic, metabolomic or proteomic events, one hopes to answer and understand biological questions and observations. This 'systems biology' approach typically involves advanced statistics to facilitate the interpretation of the data. In the present study, we demonstrate that the O2PLS multivariate regression method can be used for combining 'omics' types of data. With this methodology, systematic variation that overlaps across analytical platforms can be separated from platform-specific systematic variation. A study of Populus tremula x Populus tremuloides, investigating short-day-induced effects at transcript and metabolite levels, is employed to demonstrate the benefits of the methodology. We show how the models can be validated and interpreted to identify biologically relevant events, and discuss the results in relation to a pairwise univariate correlation approach and principal component analysis.
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| 26. |
- Carlsson, Jenny, et al.
(författare)
-
Microarray analysis reveals altered expression of a large number of nuclear genes in developing cytoplasmic male sterile Brassica napus flowers
- 2007
-
Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 49:3, s. 452-462
-
Tidskriftsartikel (refereegranskat)abstract
- To gain new insights into the mechanism underlying cytoplasmic male sterility (CMS), we compared the nuclear gene expression profiles of flowers of a Brassica napus CMS line with that of the fertile B. napus maintainer line using Arabidopsis thaliana flower-specific cDNA microarrays. The CMS line used has a B. napus nuclear genome, but has a rearranged mitochondrial (mt) genome consisting of both B. napus and A. thaliana DNA. Gene expression profiling revealed that a large number of genes differed in expression between the two lines. For example, nuclear genes coding for proteins that are involved in protein import into organelles, genes expressed in stamens and pollen, as well as genes implicated in either cell-wall remodeling or architecture, were repressed in the CMS line compared with B. napus. These results show that the mt genome of the CMS line strongly influences nuclear gene expression, and thus reveal the importance of retrograde signalling between the mitochondria and the nucleus. Furthermore, flowers of the CMS line are characterized by a replacement of stamens with carpelloid organs, and thus partially resemble the APETALA3 (AP3) and PISTILLATA (PI) mutants. In accordance with this phenotype, AP3 expression was downregulated in the stamens, shortly before these organs developed carpelloid characteristics, even though it was initiated correctly. Repression of PI succeeded that of AP3 and might be a consequence of a loss of AP3 activity. These results suggest that AP3 expression in stamens depends on proper mt function and a correct nuclear-mt interaction, and that mt alterations cause the male sterility phenotype of the CMS line.
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| 27. |
- 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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| 28. |
- Creusot, F., et al.
(författare)
-
The CIC YAC library: Sizing of the clones and determination of clones carrying repeated DNA sequences.
- 1995
-
Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 8:5, s. 763-770
-
Tidskriftsartikel (refereegranskat)abstract
- A new Arabidopsis thaliana (ecotype Columbia) genomic library has been constructed in Yeast Artificial Chromosomes: the CIC library (for CEPH, INRA and CNRS). Optimization of plant culture conditions and protoplast preparation allowed the recovery of large amounts of viable protoplasts. Mechanical shearing of DNA was minimized by isolation of DNA from protoplasts embedded in agarose. Cloning of large inserts was favored by including two successive size fractionation steps (after partial EcoRI digestion and after ligation with the vector arms), which selected DNA fragments larger than 350 kb. The library consists of 1152 clones with an average insert size of 420 kb. Clones carrying chloroplast DNA and various nuclear repeated sequences have been identified. Twenty-one per cent of the clones are found to contain chloroplast DNA. Therefore, the library represents around four nuclear genome equivalents. The clones containing 5S rDNA genes, 18S-25S rDNA sequences and the 180 bp paracentromeric repeated element account for 3.6%, 8.9% and 5.8%, respectively. Only one clone was found to carry the 160 bp paracentromeric repeated element. Given the smaller size of clones carrying Arabidopsis repeated DNA, the average size of remaining clones is around 480 kb. The library was screened by PCR amplification using pairs of primers corresponding to sequences dispersed in the genome. Seventy out of 76 pairs of primers identified from one to seven YAC clones. Thus at least 92% of the genome is represented in the CIC library. The survey of the library for clones containing unlinked DNA sequences indicates that the proportion of chimeric clones is lower than 10%.
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| 29. |
- Crocco, Carlos D, et al.
(författare)
-
AtBBX21 and COP1 genetically interact in the regulation of shade avoidance.
- 2010
-
Ingår i: The Plant journal. - 1365-313X. ; 64:4, s. 551-62
-
Tidskriftsartikel (refereegranskat)abstract
- Plants grown at high densities perceive the reduction in the ratio of red (R) to far-red (FR) light as a warning of competition. This light signal triggers morphological responses such as hypocotyl and stem elongation, and acceleration of flowering, which are known collectively as the shade-avoidance syndrome (SAS). Mutations in the photomorphogenic repressor COP1 suppress the SAS, but how COP1 modulates these responses is uncertain. We identified a new mutant with altered responses to natural shade, named lhus (long hypocotyl under shade). lhus seedlings have longer hypocotyls than wild-type under a low R:FR ratio, but not under sunlight or darkness. The lhus phenotype is due to a mutation affecting a B-box zinc finger transcription factor encoded by At1g75540, a gene previously reported as AtBBX21 that interacts with COP1 to control de-etiolation. Mutations in genes encoding other members of this protein family also result in impaired SAS regulation. Under short-term canopy shade, LHUS/BBX21 acts as positive regulator of SAS genes such as PAR1, HFR1, PIL1 and ATHB2. In contrast, global expression analysis of wild-type and lhus/bbx21 seedlings revealed that a large number of genes involved in hormonal signalling pathways are negatively regulated by LHUS/BBX21 in response to long-term canopy shade, and this observation fits well with the phenotype of lhus/bbx21 seedlings grown under a low R:FR ratio. Moreover, the bbx21 bbx22 double mutation restored the SAS in the cop1 background. We propose that LHUS/BBX21 and other B-box-containing proteins, such as BBX22, act downstream of COP1, and play a central role in early and long-term adjustment of the SAS in natural environments.
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| 30. |
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| 31. |
- Delarue, M., et al.
(författare)
-
Sur2 mutations of Arabidopsis thaliana define a new locus involved in the control of auxin homeostasis
- 1998
-
Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 14:5, s. 603-611
-
Tidskriftsartikel (refereegranskat)abstract
- A new auxin homeostasis gene in Arabidopsis called SUR2 has been identified. This gene, mapped to the bottom of chromosome 4, is defined by two recessive nuclear mutants designated superroot2 (sur2), which display several abnormalities reminiscent of auxin effects. A number of these characteristics are similar to the phenotype of the previously described auxin-overproducing mutant superroot1 (sur1); however, several lines of evidences reveal that the SUR2 gene defines a new key point in the regulation of endogenous auxin concentrations. The phenotype of the sur1 sur2 double mutant is additive. Analysis by gas chromatography coupled to mass spectrometry indicated increased levels of free indole-3-acetic acid correlated with a decreased level of bound auxin in the sur2 mutant. These results suggest that SUR2 may be involved in the control of auxin conjugation.
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| 32. |
- Endo, Satoshi, et al.
(författare)
-
Transient transformation and RNA silencing in Zinnia tracheary element differentiating cell cultures.
- 2008
-
Ingår i: The Plant journal : for cell and molecular biology. - 1365-313X. ; 53:5, s. 864-75
-
Tidskriftsartikel (refereegranskat)abstract
- The Zinnia elegans cell culture system is a robust and physiologically relevant in vitro system for the study of xylem formation. Freshly isolated mesophyll cells of Zinnia can be hormonally induced to semisynchronously transdifferentiate into tracheary elements (TEs). Although the system has proven to be valuable, its utility is diminished by the lack of an efficient transformation protocol. We herein present a novel method to introduce DNA/RNA efficiently into Zinnia cells by electroporation-based transient transformation. Using reporter gene plasmids, we optimized the system for efficiency of transformation and ability for the transformed cells to transdifferentiate into TEs. Optimal conditions included a partial digestion of the cell walls by pectolyase, a low voltage and high capacitance electrical pulse and an optimal medium to maintain cell viability during transformation. Beyond the simple expression of a reporter protein in Zinnia cells, we extended our protocol to subcellular protein targeting, simultaneous co-expression of several reporter proteins and promoter-activity monitoring during TE differentiation. Most importantly, we tested the system for double-stranded RNA (dsRNA)-induced RNA silencing. By introducing in vitro-synthesized dsRNAs, we were able to phenocopy the Arabidopsis cellulose synthase (CesA) mutants that had defects in secondary cell-wall synthesis. Suppressing the expression ofZinnia CesA homologues resulted in an increase of abnormal TEs with aberrant secondary walls. Our electroporation-based transient transformation protocol provides the suite of tools long required for functional analysis and developmental studies at single cell levels.
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| 33. |
- Ezcurra, Inés, et al.
(författare)
-
Transactivation of the Brassica napus napin promoter by ABI3 requires interaction of the conserved B2 and B3 domains of ABI3 with different cis-elements : B2 mediates activation through an ABRE, whereas B3 interacts with an RY/G-box
- 2000
-
Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 24:1, s. 57-66
-
Tidskriftsartikel (refereegranskat)abstract
- The transcriptional activator ABI3 is a key regulator of gene expression during embryo maturation in crucifers. In monocots, the related VP1 protein regulates the Em promoter synergistically with abscisic acid (ABA). We identified cis-elements in the Brassica napus napin napA promoter mediating regulation by ABI3 and ABA, by analyzing substitution mutation constructs of napA in transgenic tobacco plantlets ectopically expressing ABI3. In transient analysis using particle bombardment of tobacco leaf sections, a tetramer of the distB ABRE (abscisic acid-responsive element) mediated transactivation by ABI3 and ABI3-dependent response to ABA, whereas a tetramer of the composite RY/G complex, containing RY repeats and a G-box, mediated only ABA-independent transactivation by ABI3. Deletion of the conserved B2 and B3 domains of ABI3 abolished transactivation of napA by ABI3. The two domains of ABI3 interact with different cis-elements: B2 is necessary for ABA-independent and ABA-dependent activations through the distB ABRE, whereas B3 interacts with the RY/G complex. Thus B2 mediates the interaction of ABI3 with the protein complex at the ABRE. The regulation of napA by ABI3 differs from Em regulation by VP1, in that the B3 domain of ABI3 is essential for the ABA-dependent regulation of napA.
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| 34. |
- Fischer, Urs
(författare)
-
The heterozygous abp1/ABP1 insertional mutant has defects in functions requiring polar auxin transport and in regulation of early auxin-regulated genes
- 2011
-
Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 65, s. 282-294
-
Tidskriftsartikel (refereegranskat)abstract
- P>AUXIN-BINDING PROTEIN 1 (ABP1) is not easily accessible for molecular studies because the homozygous T-DNA insertion mutant is embryo-lethal. We found that the heterozygous abp1/ABP1 insertion mutant has defects in auxin physiology-related responses: higher root slanting angles, longer hypocotyls, agravitropic roots and hypocotyls, aphototropic hypocotyls, and decreased apical dominance. Heterozygous plants flowered earlier than wild-type plants under short-day conditions. The length of the main root, the lateral root density and the hypocotyl length were little altered in the mutant in response to auxin. Compared to wild-type plants, transcription of early auxin-regulated genes (IAA2, IAA11, IAA13, IAA14, IAA19, IAA20, SAUR9, SAUR15, SAUR23, GH3.5 and ABP1) was less strongly up-regulated in the mutant by 0.1, 1 and 10 mu m IAA. Surprisingly, ABP1 was itself an early auxin-up-regulated gene. IAA uptake into the mutant seedlings during auxin treatments was indistinguishable from wild-type. Basipetal auxin transport in young roots was slower in the mutant, indicating a PIN2/EIR1 defect, while acropetal transport was indistinguishable from wild-type. In the eir1 background, three of the early auxin-regulated genes tested (IAA2, IAA13 and ABP1) were more strongly induced by 1 mu m IAA in comparison to wild-type, but eight of them were less up-regulated in comparison to wild-type. Similar but not identical disturbances in regulation of early auxin-regulated genes indicate tight functional linkage of ABP1 and auxin transport regulation. We hypothesize that ABP1 is involved in the regulation of polar auxin transport, and thus affects local auxin concentration and early auxin gene regulation. In turn, ABP1 itself is under the transcriptional control of auxin.
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| 35. |
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| 36. |
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| 37. |
- Garcia, Christel, et al.
(författare)
-
The chloroplast protein CPSAR1, dually localized in the stroma and the inner envelope membrane, is involved in thylakoid biogenesis.
- 2010
-
Ingår i: The Plant journal. - 1365-313X. ; 63:1, s. 73-85
-
Tidskriftsartikel (refereegranskat)abstract
- Thylakoid biogenesis is a crucial step for plant development involving the combined action of many cellular actors. CPSAR1 is shown here to be required for the normal organization of mature thylakoid stacks, and ultimately for embryo development. CPSAR1 is a chloroplast protein that has a dual localization in the stroma and the inner envelope membrane, according to microscopy studies and subfractionation analysis. CPSAR1 is close to the Obg nucleotide binding protein subfamily and displays GTPase activity, as demonstrated by in vitro assays. Disruption of the CPSAR1 gene via T-DNA insertion results in the arrest of embryo development. In addition, transmission electron microscopy analysis indicates that mutant embryos are unable to develop thylakoid membranes, and remain white. Unstacked membrane structures resembling single lamellae accumulate in the stroma, and do not assemble into mature thylakoid stacks. CPSAR1 RNA interference induces partially developed thylakoids leading to pale-green embryos. Altogether, the presented data demonstrate that CPSAR1 is a protein essential for the formation of normal thylakoid membranes, and suggest a possible involvement in the initiation of vesicles from the inner envelope membrane for the transfer of lipids to the thylakoids.
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| 38. |
- Garcia-Cerdan, Jose G., et al.
(författare)
-
The PsbW protein stabilizes the supramolecular organization of photosystem II in higher plants
- 2011
-
Ingår i: The Plant Journal. - : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 65:3, s. 368-381
-
Tidskriftsartikel (refereegranskat)abstract
- PsbW, a 6.1-kDa low-molecular-weight protein, is exclusive to photosynthetic eukaryotes, and associates with the photosystem II (PSII) protein complex. In vivo and in vitro comparison of Arabidopsis thaliana wild-type plants with T-DNA insertion knock-out mutants completely lacking the PsbW protein, or with antisense inhibition plants exhibiting decreased levels of PsbW, demonstrated that the loss of PsbW destabilizes the supramolecular organization of PSII. No PSII-LHCII supercomplexes could be detected or isolated in the absence of the PsbW protein. These changes in macro-organization were accompanied by a minor decrease in the chlorophyll fluorescence parameter F-V/F-M, a strongly decreased PSII core protein phosphorylation and a modification of the redox state of the plastoquinone (PQ) pool in dark-adapted leaves. In addition, the absence of PsbW protein led to faster redox changes in the PQ pool, i.e. transitions from state 1 to state 2, as measured by changes in stationary fluorescence (F-S) kinetics, compared with the wild type. Despite these dramatic effects on macromolecular structure, the transgenic plants exhibited no significant phenotype under normal growth conditions. We suggest that the PsbW protein is located close to the minor antenna of the PSII complex, and is important for the contact and stability between several PSII-LHCII supercomplexes.
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| 39. |
- Gorzsás, András, et al.
(författare)
-
Cell specific chemotyping and multivariate imaging by combined FT-IR microspectroscopy and OPLS analysis reveals the chemical landscape of secondary xylem
- 2011
-
Ingår i: The Plant Journal. - : Blackwell Publishing Ltd. - 0960-7412 .- 1365-313X. ; 66:5, s. 903-914
-
Tidskriftsartikel (refereegranskat)abstract
- Fourier-transform infrared (FT-IR) spectroscopy combined with microscopy enables acquiring chemical information from native plant cell walls with high spatial resolution. Combined with a 64 x 64 focal plane array (FPA) detector 4096 spectra from a 0.3 x 0.3 mm image can be simultaneously obtained, where each spectrum represents a compositional and structural "fingerprint" of all cell wall components. For optimal use and analysis of such large amount of information, multivariate approaches are preferred. Here, FT-IR microspectroscopy with FPA detection is combined with orthogonal projections to latent structures discriminant analysis (OPLS-DA). This allows for 1) the extraction of spectra from specific cell types, 2) identification and characterization of different chemotypes using the full spectral information, and 3) further visualising the pattern of identified chemotypes by multivariate imaging. As proof of concept, the chemotypes of Populus tremula xylem cell types are described. The approach revealed unknown features about chemical plasticity and patterns of lignin composition in wood fibers that would have remained hidden in the dataset with traditional data analysis. The applicability of the method on Arabidopsis xylem, and its usefulness in mutant chemotyping is also demonstrated. The methodological approach is not limited to xylem tissues but can be applied to any plant organ/tissue also using other microspectroscopy techniques such as Raman- and UV-microspectroscopy.
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| 40. |
- Gorzsas, Andras, et al.
(författare)
-
Cell-specific chemotyping and multivariate imaging by combined FT-IR microspectroscopy and orthogonal projections to latent structures (OPLS) analysis reveals the chemical landscape of secondary xylem
- 2011
-
Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 66, s. 903-914
-
Tidskriftsartikel (refereegranskat)abstract
- P>Fourier-transform infrared (FT-IR) spectroscopy combined with microscopy enables chemical information to be acquired from native plant cell walls with high spatial resolution. Combined with a 64 x 64 focal plane array (FPA) detector, 4096 spectra can be simultaneously obtained from a 0.3 x 0.3 mm image; each spectrum represents a compositional and structural 'fingerprint' of all cell wall components. For optimal use and analysis of such a large amount of information, multivariate approaches are preferred. Here, FT-IR microspectroscopy with FPA detection is combined with orthogonal projections to latent structures discriminant analysis (OPLS-DA). This allows for: (i) the extraction of spectra from single cell types, (ii) identification and characterization of different chemotypes using the full spectral information, and (iii) further visualization of the pattern of identified chemotypes by multivariate imaging. As proof of concept, the chemotypes of Populus tremula xylem cell types are described. The approach revealed unknown features about chemical plasticity and patterns of lignin composition in wood fibers that would have remained hidden in the dataset with traditional data analysis. The applicability of the method to Arabidopsis xylem and its usefulness in mutant chemotyping is also demonstrated. The methodological approach is not limited to xylem tissues but can be applied to any plant organ/tissue also using other techniques such as Raman and UV microspectroscopy.
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| 41. |
- Goulas, Estelle, et al.
(författare)
-
The chloroplast lumen and stromal proteomes of Arabidopsis thaliana show differential sensitivity to short- and long-term exposure to low temperature.
- 2006
-
Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 47:5, s. 720-34
-
Tidskriftsartikel (refereegranskat)abstract
- Cold acclimation and over-wintering by herbaceous plants are energetically expensive and are dependent on functional plastid metabolism. To understand how the stroma and the lumen proteomes adapt to low temperatures, we have taken a proteomic approach (difference gel electrophoresis) to identify proteins that changed in abundance in Arabidopsis chloroplasts during cold shock (1 day), and short- (10 days) and long-term (40 days) acclimation to 5°C. We show that cold shock (1 day) results in minimal change in the plastid proteomes, while short-term (10 days) acclimation results in major changes in the stromal but few changes in the lumen proteome. Long-term acclimation (40 days) results in modulation of the proteomes of both compartments, with new proteins appearing in the lumen and further modulations in protein abundance occurring in the stroma. We identify 43 differentially displayed proteins that participate in photosynthesis, other plastid metabolic functions, hormone biosynthesis and stress sensing and signal transduction. These findings not only provide new insights into the cold response and acclimation of Arabidopsis, but also demonstrate the importance of studying changes in protein abundance within the relevant cellular compartment.
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| 42. |
- Grimberg, Åsa, et al.
(författare)
-
Cofactome analyses reveal enhanced flux of carbon into oil for potential biofuel production
- 2011
-
Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 67, s. 1018-1028
-
Tidskriftsartikel (refereegranskat)abstract
- To identify the underlying molecular basis of carbon partitioning between starch and oil we conducted 454 pyrosequencing, followed by custom microarrays to profile gene expression throughout endosperm development, of two closely related oat cultivars that differ in oil content at the expense of starch as determined by several approaches including non-invasive magnetic resonance imaging. Comparative transcriptome analysis in conjunction with metabolic profiling displays a close coordination between energy metabolism and carbon partitioning pathways, with increased demands for energy and reducing equivalents in kernels with a higher oil content. These studies further expand the repertoire of networks regulating carbon partitioning to those involved in metabolism of cofactors, suggesting that an elevated supply of cofactors, here called cofactomes, contribute to the allocation of higher carbon pools for production of oils and storage proteins. These data highlight a close association between cofactomes and carbon partitioning, thereby providing a biotechnological target for conversion of starch to oil.
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| 43. |
- Hanson, Johannes, 1969-, et al.
(författare)
-
The sucrose regulated transcription factor bZIP11 affects amino acid metabolism by regulating the expression of ASPARAGINE SYNTHETASE1 and PROLINE DEHYDROGENASE2
- 2008
-
Ingår i: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 53:6, s. 935-949
-
Tidskriftsartikel (refereegranskat)abstract
- Translation of the transcription factor bZIP11 is repressed by sucrose in a process that involves a highly conserved peptide encoded by the 5' leaders of bZIP11 and other plant basic region leucine zipper (bZip) genes. It is likely that a specific signaling pathway operating at physiological sucrose concentrations controls metabolism via a feedback mechanism. In this paper bZIP11 target processes are identified using transiently increased nuclear bZIP11 levels and genome-wide expression analysis. bZIP11 affects the expression of hundreds of genes with proposed functions in biochemical pathways and signal transduction. The expression levels of approximately 80% of the genes tested are not affected by bZIP11 promoter-mediated overexpression of bZIP11. This suggests that <20% of the identified genes appear to be physiologically relevant targets of bZIP11. ASPARAGINE SYNTHETASE1 and PROLINE DEHYDROGENASE2 are among the rapidly activated bZIP11 targets, whose induction is independent of protein translation. Transient expression experiments in Arabidopsis protoplasts show that the bZIP11-dependent activation of the ASPARAGINE SYNTHETASE1 gene is dependent on a G-box element present in the promoter. Increased bZIP11 expression leads to decreased proline and increased phenylalanine levels. A model is proposed in which sugar signals control amino acid levels via the bZIP11 transcription factor.
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| 44. |
- Hörnblad, Emma, et al.
(författare)
-
The Arabidopsis IRX10 and IRX10-LIKE glycosyltransferases are critical for glucuronoxylan biosynthesis during secondary cell wall formation
- 2009
-
Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 57, s. 718-731
-
Tidskriftsartikel (refereegranskat)abstract
- Arabidopsis IRX10 and IRX10-LIKE (IRX10-L) proteins are closely related members of the GT47 glycosyltransferase family. Single gene knock-outs of IRX10 or IRX10-L result in plants with either a weak or no mutant phenotype. However irx10 irx10-L double mutants are severely affected in their development, with a reduced rosette size and infrequent formation of a small infertile inflorescence. Plants homozygous for irx10 and heterozygous for irx10-L have an intermediate phenotype exhibiting a short inflorescence compared with the wild type, and an almost complete loss of fertility. Stem sections of the irx10 homozygous irx10-L heterozygous or irx10 irx10-L double mutants show decreased secondary cell-wall formation. NMR analysis shows that signals derived from the reducing end structure of glucuronoxylan were detected in the irx10 single mutant, and in the irx10 homozygous irx10-L heterozygous combination, but that the degree of polymerization of the xylan backbone was reduced compared with the wild type. Additionally, xylans from irx10 stem tissues have an almost complete loss of the GlcUA side chain, whereas the level of 4-O-Me-GlcUA was similar to that in wild type. Deletion of the predicted signal peptide from the N terminus of IRX10 or IRX10-L results in an inability to rescue the irx10 irx10-L double mutant phenotype. These findings demonstrate that IRX10 and IRX10-L perform a critical function in the synthesis of glucuronoxylan during secondary cell-wall formation, and that this activity is associated with the formation of the xylan backbone structure. This contrasts with the proposed function of the tobacco NpGUT1, which is closely related to the Arabidopsis IRX10 and IRX10-L proteins, in rhamnogalacturonan II biosynthesis.
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| 45. |
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| 46. |
- LIDHOLM, J, et al.
(författare)
-
A FUNCTIONAL PROMOTER SHIFT OF A CHLOROPLAST GENE - A TRANSCRIPTIONAL FUSION BETWEEN A NOVEL PSBA GENE COPY AND THE TRNK(UUU) GENE IN PINUS-CONTORTA
- 1992
-
Ingår i: The Plant Journal. - 0960-7412 .- 1365-313X. ; 2:6, s. 875-886
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Tidskriftsartikel (refereegranskat)abstract
- A comparative transcription analysis of the chloroplast trnK-psbA-trnH region of the two pine species Pinus contorta and Pinus sylvestris is reported. The chloroplast genome of P. contorta has previously been shown to contain a duplicated psbA gene copy integrated closely upstream of the split trnK gene. This rearrangement has resulted in the gene order psbAI-trnK-psbAII-trnH, where psbAII is the ancestral psbA gene copy. In P. sylvestris, a species which lacks the psbA duplication, transcription of the trnK gene originates from a position 291 bp upstream of the trnK 5' exon, adjacent to a canonical promoter structure. In P. contorta, the corresponding promoter structure has been separated from the trnK gene by the insertion of psbAI, and has, in addition, been partially deleted. Analysis of the transcriptional organization of the trnK-psbA-trnH region of the two pine species revealed that the trnK gene in P. contorta is transcriptionally fused to the inserted psbA/gene copy. As a result, trnK is under the control of the psbA promoter in this species and has therefore acquired psbA-like expression characteristics. In P. sylvestris, accumulation of trnK transcripts is not significantly higher in light-grown than in dark-grown seedlings. In contrast, the level of trnK transcripts in P. contorta is approximately 12-fold higher in the light than in the dark. When light-grown seedlings of the two pine species were compared, an approximately 20-fold higher level of trnK RNAs was found in P. contorta. In both pine species, evidence was obtained for trnK-psbA and psbA-trnH co-transcription.
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| 47. |
- Ljung, Karin
(författare)
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A role for ABCB19-mediated polar auxin transport in seedling photomorphogenesis mediated by cryptochrome 1 and phytochrome B
- 2010
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Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 62, s. 179-191
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Tidskriftsartikel (refereegranskat)abstract
- P>During seedling establishment, blue and red light suppress hypocotyl growth through the cryptochrome 1 (cry1) and phytochrome B (phyB) photosensory pathways, respectively. How these photosensory pathways integrate with growth control mechanisms to achieve the appropriate degree of stem elongation was investigated by combining cry1 and phyB photoreceptor mutations with genetic manipulations of a multidrug resistance-like membrane protein known as ABCB19 that influenced auxin distribution within the plant, as evidenced by a combination of reporter gene assays and direct auxin measurements. Auxin signaling and ABCB19 protein levels, hypocotyl growth rates, and apical hook opening were measured in mutant and wild-type seedlings exposed to a range of red and blue light conditions. Ectopic/overexpression of ABCB19 (B19OE) greatly increased auxin in the hypocotyl, which reduced the sensitivity of hypocotyl growth specifically to blue light in long-term assays and red light in high-resolution, short-term assays. Loss of ABCB19 partially suppressed the cry1 hypocotyl growth phenotype in blue light. Hypocotyl growth of B19OE seedlings in red light was very similar to phyB mutants. Altered auxin distribution in B19OE seedlings also affected the opening of the apical hook. The cry1 and phyB photoreceptor mutations both increased ABCB19 protein levels at the plasma membrane, as measured by confocal microscopy. The B19OE plant proved to be a useful tool for determining aspects of the mechanism by which light, acting through cry1 or phyB, influences the auxin transport process to control hypocotyl growth during de-etiolation.
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| 48. |
- Ljung, Karin
(författare)
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Auxin transport into cotyledons and cotyledon growth depends similarly on the ABCB19 multidrug resistance-like transporter
- 2009
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Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 60, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- ABCB19 of Arabidopsis thaliana (formerly known as MDR1 and PGP19) belongs to the Multidrug Resistance-like (MDR) or B group of the ATP-binding cassette (ABC) transporter superfamily, and mediates polar auxin transport in stems and roots. Here we have investigated the role of ABCB19 and auxin distribution in cotyledon development. During embryogenesis, confocal microscopy showed ABCB19 protein to be present in cotyledons during their main growth phase, but not later. Analysis of ProDR5:GFP expression patterns showed a significantly diminished and restricted auxin distribution pattern in abcb19 cotyledons. Nonetheless, development of abcb19 embryonic cotyledons was very similar to that of wild-type. Post-germination, ABCB19 was present in the plasma membrane of cotyledon epidermal, mesophyll and petiole cells during blade expansion. Post-germination cotyledon blade expansion in abcb19 was 65% slower than in wild-type, although the epidermal cell area was reduced by only 17%. The growth rate reduction quantitatively correlated with reduced auxin levels rather than auxin sensitivity as indicated by quantitative ProDR5:GUS assays and direct auxin measurements, and may be explained by the 50% reduction in the import of auxin through the petioles of abcb19 cotyledons during the period of maximum expansion. Taken together, these data indicate that cotyledon expansion during the establishment of photoautotrophic growth depends on ABCB19-mediated auxin import.
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| 49. |
- Ljung, Karin
(författare)
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Phytochrome interacting factors 4 and 5 control seedling growth in changing light conditions by directly controlling auxin signaling
- 2012
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Ingår i: Plant Journal. - 0960-7412 .- 1365-313X. ; 71, s. 699-711
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Tidskriftsartikel (refereegranskat)abstract
- Plant growth is strongly influenced by the presence of neighbors that compete for light resources. In response to vegetational shading shade-intolerant plants such as Arabidopsis display a suite of developmental responses known as the shade-avoidance syndrome (SAS). The phytochrome B (phyB) photoreceptor is the major light sensor to mediate this adaptive response. Control of the SAS occurs in part with phyB, which controls protein abundance of phytochrome-interacting factors 4 and 5 (PIF4 and PIF5) directly. The shade-avoidance response also requires rapid biosynthesis of auxin and its transport to promote elongation growth. The identification of genome-wide PIF5-binding sites during shade avoidance revealed that this bHLH transcription factor regulates the expression of a subset of previously identified SAS genes. Moreover our study suggests that PIF4 and PIF5 regulate elongation growth by controlling directly the expression of genes that code for auxin biosynthesis and auxin signaling components.
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| 50. |
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