Abstract

Magnaporthe oryzae is the causal agent of rice blast, one of the most serious diseases affecting rice production, and a significant threat to global food security. During plant infection, M. oryzae forms a specialised infection structure called an appressorium. The infection cell generates enormous turgor, which is focused as mechanical force to breach the rice cuticle allowing a penetration hypha to enter plant tissue. We are studying how appressoria form on the rice leaf surface and how these specialised infection cells function. Appressorium morphogenesis is tightly linked to cell cycle regulation and checkpoints govern appressorium formation and re-polarisation. Penetration peg formation involves re-organisation of the actin cytoskeleton at the base of the appressorium and is mediated by septin GTPases. Septin-mediated plant infection is controlled by NADPH oxidase activity and a regulated burst of reactive oxygen species occurs within the appressorium. The appressorium pore is also the site of polarised exocytosis during plant infection and the octameric exocyst complex localises to the pore in a septin-dependent manner and is essential for cytoskeletal regulation. I will report recent progress in understanding how appressorium function is regulated and how the rice blast fungus invades plant tissue.