Control of Plant Cell Shape by the ASB Loci in Arabidopsis

University Of Florida, Gainesville FL

Investigators

Abstract

0091393 Oppenheimer Plant cell shape plays a crucial role in plant cell function. Because of this relationship, understanding how plant cell shape is controlled is of fundamental importance to our understanding of plant cell biology. In addition, understanding how cell shape is controlled may allow the manipulation of cell shape, and hence cell function, in important crop plants for agricultural benefit. One of the best model systems for studying the control of plant cell shape is the trichome, or plant hair, on the higher plant Arabidopsis thaliana (mouse ear cress). It is well established that the cortical microtubule (MT) array plays a large role in controlling the direction of plant cell expansion which is the major determinant of plant cell shape. However, the mechanisms that organize the cortical MTs during a change in the direction of cell expansion (such as initiation of root hairs or trichome branches) remain an unresolved problem in plant biology. We are using a genetic approach to identify the genes (and ultimately the proteins) that participate in a specific, localized cell expansion event-the initiation of trichome branches. Arabidopsis trichomes are large, single cells consisting of three or four branches on a stalk. This proposal focuses on four newly discovered loci (the ASYMMETRIC BRANCH [ASB] loci) that control trichome branch position and length. Recent evidence suggests that the MT cytoskeleton plays an important role in trichome branch initiation, whereas the actin cytoskeleton plays a leading role in trichome expansion. The immediate goals of the proposed research are to test hypotheses concerning the organization of the actin and MT cytoskeletons in ASB mutants, and to determine the genetic relationship of the ASB genes (which control branch position) to the genes that control branch number. The cytoskeleton studies, along with the genetic analyses, will provide a framework for a functional dissection of the ASBgene products once the genes are cloned. Accomplishing the objectives of the proposed research will provide critical information about the mechanisms by which cell expansion is controlled. Because plant cells share cell walls and thus cannot migrate large distances during development like animal cells, the direction of cell expansion is a primary determinant of plant morphogenesis. Therefore, mechanisms by which plants control the precise spatial pattern of localized cell expansion is central to our understanding of plant development