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Cell signalling by microRNA165/6 directs gene dose-dependent root cell fate
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Physiological Botany.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Physiological Botany.
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2010 (English)In: Nature, ISSN 0028-0836, Vol. 465, no 7296, 316-321 p.Article in journal (Refereed) Published
Abstract [en]

A key question in developmental biology is how cells exchange positional information for proper patterning during organ development. In plant roots the radial tissue organization is highly conserved with a central vascular cylinder in which two water conducting cell types, protoxylem and metaxylem, are patterned centripetally. We show that this patterning occurs through crosstalk between the vascular cylinder and the surrounding endodermis mediated by cell-to-cell movement of a transcription factor in one direction and microRNAs in the other. SHORT ROOT, produced in the vascular cylinder, moves into the endodermis to activate SCARECROW. Together these transcription factors activate MIR165a and MIR166b. Endodermally produced microRNA165/6 then acts to degrade its target mRNAs encoding class III homeodomain-leucine zipper transcription factors in the endodermis and stele periphery. The resulting differential distribution of target mRNA in the vascular cylinder determines xylem cell types in a dosage-dependent manner.

Place, publisher, year, edition, pages
2010. Vol. 465, no 7296, 316-321 p.
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-136559DOI: 10.1038/nature08977ISI: 000277829200033PubMedID: 20410882OAI: oai:DiVA.org:uu-136559DiVA: diva2:377298
Available from: 2010-12-14 Created: 2010-12-13 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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