Dissecting the Molecular Pathways that Coordinate Lateral Root Initiation with Environmental Signals

University Of Chicago, Chicago IL

Investigators

Abstract

Plants are completely dependent on the resources that are available in their immediate vicinity. Unfortunately, nutrient availability and distribution are in constant flux in the environment. Plants must be able to sense these changes and respond appropriately. This developmental plasticity can be clearly observed in the plant root system. The root system is a highly branched structure that extracts water and nutrients from the soil. Both the number and placement of lateral roots are dramatically affected by environmental cues. This allows the plant to optimize its root system to its unique habitat, compete effectively for soil resources and survive adverse conditions. Lateral roots are formed from mature pericycle cells in the parent root. We have almost no understanding of how pericycle cells are triggered to re-enter the cell-cycle and re-differentiate to create the lateral root primordium. Similarly, very little is known about how certain pericycle cells are selected to proliferate while their neighbors remain quiescent. Finally, it is unclear how external conditions are sensed and the information integrated into decisions about where and when a new lateral root will be formed. The objective of this proposal is to dissect the mechanisms that regulate the initiation of lateral roots. Our main strategy involves the analysis of a lateral root initiation mutant, lin1, that we have recently isolated in Arabidopsis thaliana. While wild-type Arabidopsis plants drastically repress lateral root initiation under certain environmental conditions, the lin1 mutant maintains a highly branched root system. Furthermore, lin1 shows altered patterns of accumulation of auxin, a hormone known to be critical for lateral root initiation. We will clone the LIN1 gene and characterize the LIN1 pathway using genetic, physiological and genomic approaches. These studies will begin to shed light on one of the fundamental mysteries in plant biology: How are the decisions made that coordinate plant development with environmental cues? They will also impact our understanding of how plants are able to selectively activate cell proliferation and organogenesis during vegetative growth. By focusing on the root system, our work will also provide important insights into plant adaptation to water and nutrient stress and may lead to the development of crops able to survive under adverse conditions.