Studies of RAC GTPase-regulated organisation of the actin cytoskeleton, using the Arabidopsis trichome as a model system

The actin cytoskeleton plays a central role in plant cell morphogenesis. Polar cell growth is dependent on targeted delivery of plasma membrane and cell wall components along actin filaments. Trichomes, large leaf epidermal cells, is an attractive system to study the role of microtubules and actin filaments during cell development. The distorted group of Arabidopsis trichome mutants displays an abnormal organisation of the actin cytoskeleton and will be studied as a part of the analyses of the regulation of actin cytoskeleton organisation. The Rho/Rac family of small GTPases has become acknowledged as vital players in regulation of the actin cytoskeleton in eukaryotic cells. We have cloned the complete AtRAC gene family in Arabidopsis. Promoter studies indicate that AtRAC10 is specifically expressed during trichome development. We have also identified two of the DISTORTED genes as encoding potentially RAC-interacting proteins involved in regulation of actin polymerisation. The project aims to dissect the role of AtRAC10 and other AtRAC GTPases in regulation of the actin cytoskeleton, using Arabidopsis trichomes as a model system. We will investigate the potential interaction between AtRAC10 and target proteins employing dif ferent approaches. We also want to study the mechanism of AtRAC-mediated regulation of the actin cytoskeleton, using a combination of classical genetic, molecular biology and functional genomics tools.