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Callose Biosynthesis Regulates Symplastic Trafficking during Root Development
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2011 (English)In: Developmental Cell, ISSN 1534-5807, E-ISSN 1878-1551, Vol. 21, no 6, 1144-1155 p.Article in journal (Refereed) Published
Abstract [en]

Plant cells are connected through plasmodesmata (PD), membrane-lined channels that allow symplastic movement of molecules between cells. However, little is known about the role of PD-mediated signaling during plant morphogenesis. Here, we describe an Arabidopsis gene, CALS3/GSL12. Gain-of-function mutations in CALS3 result in increased accumulation of callose (beta-1,3-glucan) at the PD, a decrease in PD aperture, defects in root development, and reduced intercellular trafficking. Enhancement of CALS3 expression during phloem development suppressed loss-of-function mutations in the phloem abundant callose synthase, CALS7 indicating that CALS3 is a bona fide callose synthase. CALS3 alleles allowed us to spatially and temporally control the PD aperture between plant tissues. Using this tool, we are able to show that movement of the transcription factor SHORT-ROOT and microRNA1 65 between the stele and the endodermis is PD dependent. Taken together, we conclude that regulated callose biosynthesis at PD is essential for cell signaling.

Place, publisher, year, edition, pages
2011. Vol. 21, no 6, 1144-1155 p.
National Category
Natural Sciences Medical and Health Sciences
URN: urn:nbn:se:uu:diva-167203DOI: 10.1016/j.devcel.2011.10.006ISI: 000298215200018OAI: oai:DiVA.org:uu-167203DiVA: diva2:481877
Available from: 2012-01-23 Created: 2012-01-23 Last updated: 2016-04-25Bibliographically approved
In thesis
1. Cell-to-Cell Signalling in Arabidopsis Root Development
Open this publication in new window or tab >>Cell-to-Cell Signalling in Arabidopsis Root Development
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Development in multicellular organisms requires a strict balance between cell division and differentiation. The simple architecture of the Arabidopsis thaliana root makes it an ideal model for studying molecular mechanisms controlling both the transition from cell division to cell differentiation and cell fate determination. The class III Homeodomain-Leucine Zipper (HD-ZIP III) transcription factors (TFs) are well known developmental regulators, controlling important aspects of embryogenesis, shoot meristem activity, leaf polarity and vascular patterning. The HD-ZIP III TFs are under post-transcriptional control of microRNA165 (miR165) and miR166. In this thesis, I present a cell-to-cell signalling pathway underlying root vascular patterning and describe signaling pathways downstream of the HD-ZIP III TFs in their control of root development. The TF SHORTROOT (SHR), moves from the vascular stele cells to the surrounding endodermal cell layer. We show that SHR acts here to transcriptionally activate MIR165A and MIR166B, and the miR165/6 produced in the endodermis act non-cell autonomously to post-transcriptionally restrict HD-ZIP III mRNA levels in the peripheral stele. The resulting graded HD-ZIP III activity domain in the radial stele dose-dependently determines vascular cell type; high levels of HD-ZIP III in the central stele result in metaxylem formation while lower levels in the peripheral stele result in protoxylem. We provide evidence that the HD-ZIP III factors act as de novo xylem specifiers, because the quintuple mutant lacking all five HD-ZIP III genes forms no xylem. Furthermore, reducing the plasmodesmatal aperture through callose accumulation inhibits the bi-directional mobility of both signalling molecules, providing evidence that both SHR and miR165/6 move cell-to-cell via plasmodesmata to control root development.

I present downstream components of the miR165/HD-ZIP III TFs in the root meristem, identified through a time-course induction of miR165 coupled to transcriptome analyses. This experiment revealed novel roles for HD-ZIP III TFs in vascular patterning and meristem size control. I show that HD-ZIP III directed repression of auxin hormone signalling in the xylem axis is essential for proper xylem differentiation. Furthermore, I provide data to show that they also control the balance of reactive oxygen species in the root meristem, thereby directing meristem size and ultimately controlling root growth.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 61 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 979
HD-ZIP III, miRNA, plasmodesmata, auxin, ROS, xylem
National Category
Cell Biology Developmental Biology Botany
Research subject
Biology with specialization in Physiological Botany
urn:nbn:se:uu:diva-181187 (URN)978-91-554-8487-3 (ISBN)
Public defence
2012-11-16, A281, Uppsala BioCenter, Almas Allé 5, Uppsala, 13:00 (English)
Available from: 2012-10-26 Created: 2012-09-18 Last updated: 2013-01-23

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Roberts, Christina J.Carlsbecker, Annelie
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