RIP proteins of barley interact with the susceptibility factor RACB and distinctively localize in epidermal cells
C. MCCOLLUM (1), C. Höfle (1), R. Hueckelhoven (2) (1) Technische Universität München, Germany; (2) Technische Universität München, Germany

Small monomeric G-Proteins of the RAC/ROP class function as molecular switches in plant cells. They can change between an active GTP-bound stage and an inactive GDP-bound stage. RAC/ROPs are key regulators in many polarization processes in plant cell development, for example root hair initiation and pollen tube elongation. RACB was shown to be a susceptibility factor in the interaction of barley and the barley powdery mildew Blumeria graminis f. sp. hordei. During defense against and accommodation of B. graminis, cellular polarization is also essential, which can be observed as the concentration of different cytoplasmic components, especially the cytoskeleton, at the site of attack. In order to analyze the mechanism by which RACB mediates powdery mildew susceptibility in barley we wanted to identify proteins that act downstream of RACB. We found three ROP interactive partners (RIPs) in barley, which are considered as scaffold proteins in ROP signaling. We could show that the three RIP proteins of barley (RIPa, RIPb, RIPc) interact with active and wild type forms of different barley RAC/ROP isoforms in yeast but not with dominant negative forms. By transient overexpression of RIPs tagged with different fluorophores in epidermal cells we found distinct localization patterns in presence of active or inactive RACB. In transient expression assays we could also show that overexpression of RIPb renders barley more susceptible to penetration by B. graminis.

Abstract Number: C11-4, P7-153
Session Type: Concurrent