GUADALUPE VALDOVINOS- PONCE

Rice (Oryza sativa L.) production worldwide is constrained by rice blast disease caused by the ascomycetous fungus Magnaporthe oryzae. Rice blast has become a model system for the study of fungal plant diseases based on its global relevance to agriculture and on our ability to apply molecular genetic and genomic analyses to both the pathogen and the plant. We have applied molecular and cellular analyses to understand critical processes in the M. oryzae disease cycle. The dark melanin pigment produced by the fungus is critical for the function of its specialized appressorial cell, which punches the leaf surface by generating the highest pressure known in any biological system, estimated at 80 times the atmospheric pressure. Without melanin, the fungus can neither generate this pressure nor puncture the plant surface and disease does not occur. M. oryzae genome sequencing identified a cluster of melanin biosynthesis genes that included an attractive candidate for the transcription factor that regulates melanin biosynthesis in appressoria. We report the structural and functional characterization of this putative transcription factor, although its role remains elusive. Host cellular responses after appressorial penetration are equally important in determining if disease will occur. We hav