The molecular basis of root gravitropism

Background and Objectives
This project addresses fundamental question in plant biology, that of how plants are able to orient their growth with reference to gravity. In particular, the project seeks to identify the mechanistic basis of the angle-dependent gravitropic response, a phenomenon observed throughout the higher plants. Our recent work has shown that this angle-dependent gravitropism is central to the ability of plants to maintain root and shoot branches at specific growth angles. The project builds on an exciting mathematical model of angle-dependent graviresponse developed in a previous DTP project supervised by Kepinski and Cohen. This mechanistic model makes specific predictions about growth dynamics that give rise to angle-dependence in graviresponse, and has proved essential in guiding the experimental work and interpreting our results. This project will test those predictions and, through new forward genetic screens, extend the genetic framework of our understanding of the process of gravitropism.

Novelty and Timeliness
The complimentary resources of the Peckham, Cohen, and Kepinski labs making them uniquely placed to make the crucial breakthrough from qualitative and descriptive to rigorous, quantitative, mechanistic, multiscale understanding the fundamental basis of gravitropism.

Experimental Approach
By employing the outstanding imaging capabilities of the Peckham group to fully exploit genetic and molecular genetic resources developed in the Kepinski lab, we will relate, in real-time, the molecular events within gravity-sensing cells to the generation of the auxin asymmetries that drive tropic growth in the root. Further, suppressor screens based on novel gravitropism mutants identified in the Kepinski lab will be employed to identify