| 1. |
- Muñiz, Luis, et al.
(författare)
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ACAULIS5 controls Arabidopsis xylem specification through the prevention of premature cell death
- 2008
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 135:15, s. 2573-2582
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Tidskriftsartikel (refereegranskat)abstract
- Cell size and secondary cell wall patterning are crucial for the proper functioning of xylem vessel elements in the vascular tissues of plants. Through detailed anatomical characterization of Arabidopsis thaliana hypocotyls, we observed that mutations in the putative spermine biosynthetic gene ACL5 severely affected xylem specification: the xylem vessel elements of the acl5 mutant were small and mainly of the spiral type, and the normally predominant pitted vessels as well as the xylem fibers were completely missing. The cell-specific expression of ACL5 in the early developing vessel elements, as detected by in situ hybridization and reporter gene analyses, suggested that the observed xylem vessel defects were caused directly by the acl5 mutation. Exogenous spermine prolonged xylem element differentiation and stimulated cell expansion and cell wall elaboration in xylogenic cell cultures of Zinnia elegans, suggesting that ACL5 prevents premature death of the developing vessel elements to allow complete expansion and secondary cell wall patterning. This was further supported by our observations that the vessel elements of acl5 seemed to initiate the cell death program too early and that the xylem defects associated with acl5 could be largely phenocopied by induction of premature, diphtheria toxin-mediated cell death in the ACL5-expressing vessel elements. We therefore provide, for the first time, mechanistic evidence for the function of ACL5 in xylem specification through its action on the duration of xylem element differentiation.
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| 2. |
- Vera-Sirera, Francisco, et al.
(författare)
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A bHLH-Based Feedback Loop Restricts Vascular Cell Proliferation in Plants
- 2015
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Ingår i: Developmental Cell. - : Elsevier BV. - 1534-5807 .- 1878-1551. ; 35:4, s. 432-443
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Tidskriftsartikel (refereegranskat)abstract
- Control of tissue dimensions in multicellular organisms requires the precise quantitative regulation of mitotic activity. In plants, where cells are immobile, tissue size is achieved through control of both cell division orientation and mitotic rate. The bHLH transcription factor heterodimer formed by TARGET OF MONOPTEROS5 (TMO5) and LONESOME HIGHWAY (LHVV) is a central regulator of vascular width-increasing divisions. An important unanswered question is how its activity is limited to specify vascular tissue dimensions. Here we identify a regulatory network that restricts TMO5/LHW activity. We show that thermospermine synthase ACAULIS5 antagonizes TMO5/LHW activity by promoting the accumulation of SAC51-LIKE (SACL) bHLH transcription factors. SACL proteins heterodimerize with LHW therefore likely competing with TMO5/LHW interactions prevent activation of TMO5/LHW target genes, and suppress the over-proliferation caused by excess TMO5/LHW activity. These findings connect two thus-far disparate pathways and provide a mechanistic understanding of the quantitative control of vascular tissue growth.
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| 3. |
- Vera-Sirera, Francisco, et al.
(författare)
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Role of polyamines in plant vascular development
- 2010
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 48:7, s. 534-539
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Tidskriftsartikel (refereegranskat)abstract
- Several pieces of evidence suggest a role for polyamines in the regulation of plant vascular development. For instance, polyamine oxidase gene expression has been shown to be associated with lignification, and downregulation of S-adenosylmethionine decarboxylase causes dwarfism and enlargement of the vasculature. Recent evidence from Arabidopsis thaliana also suggests that the active polyamine in the regulation of vascular development is the tetraamine thermospermine. Thermospermine biosynthesis is catalyzed by the aminopropyl transferase encoded by ACAULIS5, which is specifically expressed in xylem vessel elements. Both genetic and molecular evidence support a fundamental role for thermospermine in preventing premature maturation and death of the xylem vessel elements. This safeguard action of thermospermine has significant impact on xylem cell morphology, cell wall patterning and cell death as well as on plant growth in general. This manuscript reviews recent reports on polyamine function and places polyamines in the context of the known regulatory mechanisms that govern vascular development. (C) 2010 Elsevier Masson SAS. All rights reserved.
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