Regulation of root meristem differentiation by cell wall composition

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Plant cells are surrounded by cell walls that give structure to the plant and serve many functions, including determining the ultimate size and biomass of the plant body. Composition of cell walls has an impact on these important structural and functional roles, particularly when cells are first growing and differentiating into new cell types. How this occurs is not well understood, particularly in roots, which are not readily accessible for study. Several factors contribute to the growth, expansion and differentiation of root cells including the local soil environment, internal plant hormones, and other developmental events in the plant. This project focuses on understanding the role of hormones in contributing to important changes in root cell wall composition during differentiation. By uncovering the molecular pathways in root cells associated with hormone action, the project will clarify how cell walls respond to growth hormone signals. Understanding the molecular underpinnings of changes in cell wall composition during root differentiation will provide basic knowledge that can be used ultimately to manage plant growth to optimize biomass, ensure food security, and stabilize plants as critical renewable resources for the nation. Through training, education and outreach opportunities at all levels, the project will support the mentoring and education of next generation of scientists, including undergraduate, graduate students and post-doctoral scholars Post-embryonic plant development relies on meristem populations in the shoot and root. It has long been appreciated that auxin-induced changes in cell walls mediate cell elongation and/or division within meristems. In the primary root apical meristem (RAM), auxin positively regulates the stem cell niche and influences differentiation of various progenitor cells, including distal columella cells, lateral root cap/epidermal initials, cortex/endodermal initials and vasculature initials. An unanswered question is how auxin regulates cell wall properties in the RAM as progenitor cells differentiate from the quiescent center. It is not well understood how cell wall composition changes as RAM cell differentiation occurs. The research team has recently identified an auxin regulated galacturonosyltransferase, GAUT10, which regulates RAM size in a sucrose-dependent manner. This project focuses on testing the hypothesis that GAUT10 plays a key role in cell-wall-mediated auxin regulation of root apical meristem differentiation. This hypothesis will be tested by three aims: (1) Determination of how GAUT10 influences RAM cell wall structure, (2) Characterization of how GAUT10 regulates root stem cell differentiation, and (3) Identification of how GAUT10 is regulated by auxin in roots. The proposed studies will result in novel mechanistic insights regarding how auxin influences cell wall properties to regulate root development using in vivo, in vitro and in silico strategies applied to multi-scale systems, including recombinant proteins, plant and yeast cells, and whole Arabidopsis roots.This project is jointly funded by the Plant, Fungal and Microbial Development program in the Developmental Systems Cluster in the Division of Integrative Organismal Systems (IOS) and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.