Mitotic control and autophagic-programmed cell death are required for appressorium-mediated penetration in Magnaporthe grisea
C. Veneault-Fourrey, N. J. Talbot
School of Biosciences University of Exeter, Washington Singer Laboratories, Perry Road, Exeter, EX4 4QG, UNITED KINGDOM
The rice blast fungus Magnaporthe grisea elaborates a specialised infection structure called an appressorium in order to infect rice leaves. Previously, it was reported that mitosis occurs in the germ tube prior to appressorium development (1). However, little emphasis has been placed on investigating the importance of this event in appressorium morphogenessi. We have used both pharmacological and genetic approaches in order to block mitosis. We showed that mitosis is required for infection-related development to proceed in Magnaporthe grisea. Mitosis occurs in the germ tube and one of the two daughter nuclei migrates to the appressorium and the other into conidium. The conidium then collapses and nuclei degenerate. We have shown that the collapse of conidia occurs by a programmed autophagic (type II) cell death mechanism. Furthermore, our results showed that autophagy is required for pathogenicity.
(1) Bourett and Howard, 1990, Can. J. Bot. 68, 329-342