ArabidopsisTyrosylprotein Sulfotransferase Acts in the Auxin/PLETHORA Pathway in Regulating Postembryonic Maintenance of the Root Stem Cell Niche

Wenkun Zhou,Qian Chen,Chun-Ming Liu,Jiaqiang Sun,Jinfang Chu,Lihuang Zhu,Lirong Wei,Jian Xu,Qingzhe Zhai,Chuanyou Li,Hongling Jiang,Rong Chen

doi:10.1105/tpc.110.075721

Abstract

Recent identification of the Arabidopsis thaliana tyrosylprotein sulfotransferase (TPST) and a group of Tyr-sulfated peptides known as root meristem growth factors (RGFs) highlights the importance of protein Tyr sulfation in plant growth and development. Here, we report the action mechanism of TPST in maintenance of the root stem cell niche, which in the Arabidopsis root meristem is an area of four mitotically inactive quiescent cells plus the surrounding mitotically active stem cells. Mutation of TPST leads to defective maintenance of the root stem cell niche, decreased meristematic activity, and stunted root growth. We show that TPST expression is positively regulated by auxin and that mutation of this gene affects auxin distribution by reducing local expression levels of several PIN genes and auxin biosynthetic genes in the stem cell niche region. We also show that mutation of TPST impairs basal- and auxin-induced expression of the PLETHORA (PLT) stem cell transcription factor genes and that overexpression of PLT2 rescues the root meristem defects of the loss-of-function mutant of TPST. Together, these results support that TPST acts to maintain root stem cell niche by regulating basal- and auxin-induced expression of PLT1 and PLT2. TPST-dependent sulfation of RGFs provides a link between auxin and PLTs in regulating root stem cell niche maintenance.

Highlights

Plant root growth is maintained by the continuous division of cells in the meristem
tyrosylprotein sulfotransferase (TPST)-Dependent Sulfation of root meristem growth factors (RGFs) Is Required for Postembryonic Maintenance of the Root Stem Cell Niche
TPST is distinct from the SHR/SCR and the PLT transcription factors, which affect the establishment of the root stem cell niche during embryonic pattern formation

Summary

Introduction

Plant root growth is maintained by the continuous division of cells in the meristem. Within the root meristem, the mitotically inactive quiescent center (QC) cells (four in Arabidopsis thaliana), together with the surrounding stem cells, constitute the root stem cell niche, which provides the source of cells for all tissues in roots (van den Berg et al, 1995; Scheres, 2007; Dinneny and Benfey, 2008; Kornet and Scheres, 2009). The auxin inducible PLETHORA1 (PLT1) and PLT2 genes, which encode members of the AP2 class of transcription factors that are essential for root stem cell niche patterning (Aida et al, 2004; Galinha et al, 2007), are potential candidates for such translations (Benjamins and Scheres, 2008). PLT genes maintain PIN transcription, which stabilizes the position of the stem cell niche (Blilou et al, 2005; Grieneisen et al, 2007; Dinneny and Benfey, 2008). How auxin transport and local auxin biosynthesis are coordinated remains a mystery, but it is generally believed that both processes function together to establish a state of auxin homeostasis that is required for stem cell patterning and maintenance in roots (Jiang and Feldman, 2003; Zhao, 2010)

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Conclusion