| 1. |
- Baral, Anirban
(författare)
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The TGN/EE SNARE protein SYP61 and the ubiquitin ligase ATL31 cooperatively regulate plant responses to carbon/nitrogen conditions in Arabidopsis
- 2022
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 34, s. 1354-1374
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Tidskriftsartikel (refereegranskat)abstract
- The TGN/EE SNARE protein SYP61 plays a critical role in plant carbon/nitrogen nutrient stress responses and is ubiquitinated in response to low carbon/high nitrogen conditions.Ubiquitination is a post-translational modification involving the reversible attachment of the small protein ubiquitin to a target protein. Ubiquitination is involved in numerous cellular processes, including the membrane trafficking of cargo proteins. However, the ubiquitination of the trafficking machinery components and their involvement in environmental responses are not well understood. Here, we report that the Arabidopsis thalianatrans-Golgi network/early endosome localized SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein SYP61 interacts with the transmembrane ubiquitin ligase ATL31, a key regulator of resistance to disrupted carbon (C)/nitrogen/(N)-nutrient conditions. SYP61 is a key component of membrane trafficking in Arabidopsis. The subcellular localization of ATL31 was disrupted in knockdown mutants of SYP61, and the insensitivity of ATL31-overexpressing plants to high C/low N-stress was repressed in these mutants, suggesting that SYP61 and ATL31 cooperatively function in plant responses to nutrient stress. SYP61 is ubiquitinated in plants, and its ubiquitination level is upregulated under low C/high N-nutrient conditions. These findings provide important insights into the ubiquitin signaling and membrane trafficking machinery in plants.
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| 2. |
- Blaschek, Leonard, et al.
(författare)
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Different combinations of laccase paralogs nonredundantly control the amount and composition of lignin in specific cell types and cell wall layers in Arabidopsis
- 2023
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 35:2, s. 889-909
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Tidskriftsartikel (refereegranskat)abstract
- Vascular plants reinforce the cell walls of the different xylem cell types with lignin phenolic polymers. Distinct lignin chemistries differ between each cell wall layer and each cell type to support their specific functions. Yet the mechanisms controlling the tight spatial localization of specific lignin chemistries remain unclear. Current hypotheses focus on control by monomer biosynthesis and/or export, while cell wall polymerization is viewed as random and nonlimiting. Here, we show that combinations of multiple individual laccases (LACs) are nonredundantly and specifically required to set the lignin chemistry in different cell types and their distinct cell wall layers. We dissected the roles of Arabidopsis thaliana LAC4, 5, 10, 12, and 17 by generating quadruple and quintuple loss-of-function mutants. Loss of these LACs in different combinations led to specific changes in lignin chemistry affecting both residue ring structures and/or aliphatic tails in specific cell types and cell wall layers. Moreover, we showed that LAC-mediated lignification has distinct functions in specific cell types, waterproofing fibers, and strengthening vessels. Altogether, we propose that the spatial control of lignin chemistry depends on different combinations of LACs with nonredundant activities immobilized in specific cell types and cell wall layers.
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| 3. |
- Bozhkov, Peter
(författare)
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Focus on biomolecular condensates
- 2023
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Ingår i: Plant Cell. - 1040-4651 .- 1532-298X. ; 35, s. 3155-3157
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Tidskriftsartikel (refereegranskat)
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| 4. |
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| 5. |
- Doyle, Siamsa, et al.
(författare)
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Cell biology of the leaf epidermis: fate specification, morphogenesis, and coordination
- 2022
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 34, s. 209-227
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Forskningsöversikt (refereegranskat)abstract
- As the outermost layer of plants, the epidermis serves as a critical interface between plants and the environment. During leaf development, the differentiation of specialized epidermal cell types, including stomatal guard cells, pavement cells, and trichomes, occurs simultaneously, each providing unique and pivotal functions for plant growth and survival. Decades of molecular-genetic and physiological studies have unraveled key players and hormone signaling specifying epidermal differentiation. However, most studies focus on only one cell type at a time, and how these distinct cell types coordinate as a unit is far from well-comprehended. Here we provide a review on the current knowledge of regulatory mechanisms underpinning the fate specification, differentiation, morphogenesis, and positioning of these specialized cell types. Emphasis is given to their shared developmental origins, fate flexibility, as well as cell cycle and hormonal controls. Furthermore, we discuss computational modeling approaches to integrate how mechanical properties of individual epidermal cell types and entire tissue/organ properties mutually influence each other. We hope to illuminate the underlying mechanisms coordinating the cell differentiation that ultimately generate a functional leaf epidermis.
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| 6. |
- Dziasek, Katarzyna, et al.
(författare)
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Bypassing reproductive barriers in hybrid seeds using chemically induced epimutagenesis
- 2021
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 34, s. 989-1001
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Tidskriftsartikel (refereegranskat)abstract
- Genome-wide loss of DNA methylation induced by 5-Azacytidine allows interploidy and interspecific hybridization barriers to be bypassed in Arabidopsis and Capsella.The triploid block, which prevents interploidy hybridizations in flowering plants, is characterized by a failure in endosperm development, arrest in embryogenesis, and seed collapse. Many genetic components of triploid seed lethality have been successfully identified in the model plant Arabidopsis thaliana, most notably the paternally expressed genes (PEGs), which are upregulated in tetraploid endosperm with paternal excess. Previous studies have shown that the paternal epigenome is a key determinant of the triploid block response, as the loss of DNA methylation in diploid pollen suppresses the triploid block almost completely. Here, we demonstrate that triploid seed collapse is bypassed in Arabidopsis plants treated with the DNA methyltransferase inhibitor 5-Azacytidine during seed germination and early growth. We identified strong suppressor lines showing stable transgenerational inheritance of hypomethylation in the CG context, as well as normalized expression of PEGs in triploid seeds. Importantly, differentially methylated loci segregate in the progeny of "epimutagenized" plants, which may allow epialleles involved in the triploid block response to be identified in future studies. Finally, we demonstrate that chemically induced epimutagenesis facilitates hybridization between different Capsella species, thus potentially emerging as a strategy for producing triploids and interspecific hybrids with high agronomic interest.
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| 7. |
- Hicks, Glenn
(författare)
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Endosidin20 Targets the Cellulose Synthase Catalytic Domain to Inhibit Cellulose Biosynthesis
- 2020
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 32, s. 2141-2157
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Tidskriftsartikel (refereegranskat)abstract
- The cellulose synthase inhibitor Endosidin20 is an excellent tool for manipulating cellulose synthesis in order to produce cellulose products with desired properties and to control weeds. Plant cellulose is synthesized by rosette-structured cellulose synthase (CESA) complexes (CSCs). Each CSC is composed of multiple subunits of CESAs representing three different isoforms. Individual CESA proteins contain conserved catalytic domains for catalyzing cellulose synthesis, other domains such as plant-conserved sequences, and class-specific regions that are thought to facilitate complex assembly and CSC trafficking. Because of the current lack of atomic-resolution structures for plant CSCs or CESAs, the molecular mechanism through which CESA catalyzes cellulose synthesis and whether its catalytic activity influences efficient CSC transport at the subcellular level remain unknown. Here, by performing chemical genetic analyses, biochemical assays, structural modeling, and molecular docking, we demonstrate that Endosidin20 (ES20) targets the catalytic site of CESA6 in Arabidopsis (Arabidopsis thaliana). Chemical genetic analysis revealed important amino acids that potentially participate in the catalytic activity of plant CESA6, in addition to previously identified conserved motifs across kingdoms. Using high spatiotemporal resolution live cell imaging, we found that inhibiting the catalytic activity of CESA6 by ES20 treatment reduced the efficiency of CSC transport to the plasma membrane. Our results demonstrate that ES20 is a chemical inhibitor of CESA activity and trafficking that represents a powerful tool for studying cellulose synthesis in plants.
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| 8. |
- Hoffmann, Gesa, et al.
(författare)
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Arabidopsis RNA processing body components LSM1 and DCP5 aid in the evasion of translational repression during Cauliflower mosaic virus infection
- 2022
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Ingår i: The Plant Cell. - : Oxford University Press. - 1040-4651 .- 1532-298X. ; 34:8, s. 3128-3147
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Tidskriftsartikel (refereegranskat)abstract
- Viral infections impose extraordinary RNA stress, triggering cellular RNA surveillance pathways such as RNA decapping, nonsense-mediated decay, and RNA silencing. Viruses need to maneuver among these pathways to establish infection and succeed in producing high amounts of viral proteins. Processing bodies (PBs) are integral to RNA triage in eukaryotic cells, with several distinct RNA quality control pathways converging for selective RNA regulation. In this study, we investigated the role of Arabidopsis thaliana PBs during Cauliflower mosaic virus (CaMV) infection. We found that several PB components are co-opted into viral factories that support virus multiplication. This pro-viral role was not associated with RNA decay pathways but instead, we established that PB components are helpers in viral RNA translation. While CaMV is normally resilient to RNA silencing, dysfunctions in PB components expose the virus to this pathway, which is similar to previous observations for transgenes. Transgenes, however, undergo RNA quality control-dependent RNA degradation and transcriptional silencing, whereas CaMV RNA remains stable but becomes translationally repressed through decreased ribosome association, revealing a unique dependence among PBs, RNA silencing, and translational repression. Together, our study shows that PB components are co-opted by the virus to maintain efficient translation, a mechanism not associated with canonical PB functions.
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| 9. |
- Hoffmann, Gesa, et al.
(författare)
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Cauliflower mosaic virus protein P6 is a multivalent node for RNA granule proteins and interferes with stress granule responses during plant infection
- 2023
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Ingår i: The Plant Cell. - : Oxford University Press. - 1040-4651 .- 1532-298X. ; 35:9, s. 3363-3382
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Tidskriftsartikel (refereegranskat)abstract
- Biomolecular condensation is a multipurpose cellular process that viruses use ubiquitously during their multiplication. Cauliflower mosaic virus replication complexes are condensates that differ from those of most viruses, as they are nonmembranous assemblies that consist of RNA and protein, mainly the viral protein P6. Although these viral factories (VFs) were described half a century ago, with many observations that followed since, functional details of the condensation process and the properties and relevance of VFs have remained enigmatic. Here, we studied these issues in Arabidopsis thaliana and Nicotiana benthamiana. We observed a large dynamic mobility range of host proteins within VFs, while the viral matrix protein P6 is immobile, as it represents the central node of these condensates. We identified the stress granule (SG) nucleating factors G3BP7 and UBP1 family members as components of VFs. Similarly, as SG components localize to VFs during infection, ectopic P6 localizes to SGs and reduces their assembly after stress. Intriguingly, it appears that soluble rather than condensed P6 suppresses SG formation and mediates other essential P6 functions, suggesting that the increased condensation over the infection time-course may accompany a progressive shift in selected P6 functions. Together, this study highlights VFs as dynamic condensates and P6 as a complex modulator of SG responses.
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| 10. |
- Kimura, Sachie, et al.
(författare)
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CRK2 and C-terminal phosphorylation of NADPH oxidase RBOHD regulate reactive oxygen species production in arabidopsis
- 2020
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Ingår i: Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 32:4, s. 1063-1080
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Tidskriftsartikel (refereegranskat)abstract
- Reactive oxygen species (ROS) are important messengers in eukaryotic organisms, and their production is tightly controlled. Active extracellular ROS production by NADPH oxidases in plants is triggered by receptor-like protein kinase-dependent signaling networks. Here, we show that CYSTEINE-RICH RLK2 (CRK2) kinase activity is required for plant growth and CRK2 exists in a preformed complex with the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) in Arabidopsis (Arabidopsis thaliana). Functional CRK2 is required for the full elicitor-induced ROS burst, and consequently the crk2 mutant is impaired in defense against the bacterial pathogen Pseudomonas syringae pv tomato DC3000. Our work demonstrates that CRK2 regulates plant innate immunity. We identified in vitro CRK2-dependent phosphorylation sites in the C-terminal region of RBOHD. Phosphorylation of S703 RBOHD is enhanced upon flg22 treatment, and substitution of S703 with Ala reduced ROS production in Arabidopsis. Phylogenetic analysis suggests that phospho-sites in the C-terminal region of RBOHD are conserved throughout the plant lineage and between animals and plants. We propose that regulation of NADPH oxidase activity by phosphorylation of the C-terminal region might be an ancient mechanism and that CRK2 is an important element in regulating microbe-associated molecular pattern-triggered ROS production.
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