Arabidopsis Trichome Morphogenesis: A Genetic Approach to Studying Cytoskeletal Function

Abstract

Arabidopsis trichome (leaf hair) development is being used to genetically dissect cytoskeletal organization and function in plant cells. The highly constrained and distinct requirements for microtubule and microfilament function during trichome morphogenesis make it possible to screen for mutations that affect cytoskeletal function. Pharmacological drugs that disrupt normal microtubule dynamics block the establishment of polarized trichome growth. In contrast, drugs that alter F-actin organization or dynamics affect the maintenance and coordination of the normal pattern of cell growth at later stages of morphogenesis. There are distinct classes of trichome morphology mutants that appear to affect either the microtubule or the microfilament-dependent phases of trichome morphogenesis. For example, the zwichel (zwi) mutant displays altered trichome stalk expansion and branch initiation that is similar to the effects of microtubule-disrupting agents. The ZWI gene encodes a kinesin-like microtubule motor protein. The cell shape defects of the distorted group of trichome morphology mutants are phenocopied by exposing developing trichomes to drugs that disrupt the actin cytoskeleton, but not those that affect microtubule-disrupting agents. Distorted mutants fail to maintain polarized growth during discrete stages of trichome development. The combination of molecular genetic and cell biology tools will help to uncover the mechanisms of cytoskeletal organization and function in plant cells.