Microtubule-organization during fungal invasion into barley epidermal cells

Plant parasitic fungi exert diverse strategies for overcoming plant innate immunity. In the case of biotrophic fungi, the parasite additionally manipulates host cellular function for establishment and maintenance of infection structures in intact living host cells. This involves hostile control of plant mechanisms to control subcellular architecture and function. We identified host small RAC/ROP G-proteins (barley RACB) and microtubules to be key to the question of fungal success or failure in establishing parasitism. In this project, we aim at filling the knowledge gap between grass RAC/ROP proteins and microtubule organization in plant-fungus interaction. To this end, we are going to make use of the recently published sequence information of the barley genome. We will use this information for identification of RAC/ROP executor proteins which organize the microtubule cytoskeleton and control penetration success of the biotrophic ascomycete fungus Blumeria graminis f.sp. hordei. Candidate proteins (RIPs and RICs) were identified because of their protein domains conserved for interaction with RAC/ROPs and/or with microtubules. We are going to demonstrate interaction of RICs or RIPs with RACB in yeast and in planta. We study protein function by transient induced gene silencing and over-expression in barley epidermal cells followed by challenge inoculation with conidia of Blumeria graminis f.sp. hordei. Fluorescent-tagged versions of RICs and RIPs are transiently expressed to study subcellular localization dependent on fungal attack and/or depending on ectopic activation of upstream RAC/ROPs. Live cell imaging will illustrate MT organization influenced by function and abundance of RAC/ROPs as well as RICs or RIPs. This will demonstrate the potential of barley RICs and RIPs to influence MT arrays downstream of RAC/ROPs and during fungal penetration.