Investigating the cell biology of appressorium-mediated plant infection and tissue invasion by the rice blast fungus Magnaporthe oryzae
N. TALBOT (1), L. Ryder (1), X. Yan (1), M. Oses-Ruiz (1), W. Sakulkoo (1), M. Kershaw (1), M. Martin-Urdiroz (1), D. Soanes (1) (1) University of Exeter, United Kingdom

Magnaporthe oryzae is the causal agent of rice blast, one of the most serious diseases affecting rice production. During plant infection, M. oryzae forms a specialised infection structure called an appressorium. We have observed that a single round of mitosis always occurs prior to appressorium morphogenesis and precedes autophagic cell death of the three-celled conidium, which is necessary for plant infection. An S-phase checkpoint, that requires the DNA damage repair pathway, is necessary for initiation of appressorium development. Re-polarisation of the appressorium requires a second S-phase checkpoint, regulated in a novel turgor-driven manner. A hetero-oligomeric septin GTPase complex scaffolds a toroidal F-actin network at the base of the appressorium that allows the host cuticle to be breached and leads to invasion of epidermal cells by biotrophic invasive hyphae. A specialised Nox2 NADPH oxidase-tetraspanin complex is necessary for septin-mediated control of actin dynamics. Once tissue is invaded the fungus undergoes differential expression and secretion of a large repertoire of effector proteins destined either for the apoplastic space which surrounds invasive hyphae, or directed instead into plant cells.  Cell-to-cell movement via plasmodesmata-rich pit field sites is mediated by a MAP kinase-dependent regulatory pathway that suppresses host immunity and facilitates a septin-dependent constriction of hyphae as they move to new host cells    

Abstract Number: S2-1
Session Type: Special Session