P-156 - The Bip1 transcriptional regulator is controlled by the pathogenicity Pmk1 MAPK pathway in Magnaporthe oryzae

Rice blast disease, caused by the filamentous fungus Magnaporthe oryzae, poses a significant threat to global rice production. To invade its host, the fungus secretes a battery of effector proteins with diverse functions and sub-cellular targets. In M. oryzae, the regulation of effector gene expression has been linked to multiple interconnected signalling pathways, including the cyclic AMP (cAMP)-dependent protein kinase A pathway, Pmk1 MAPK signalling, the cell wall integrity pathway, and epigenetic modifications. These pathways integrate environmental cues to coordinate fungal morphogenesis with effector gene expression, highlighting a sophisticated regulatory network that leads to host colonisation. Here, we demonstrate that the transcription factor Bip1 (B-ZIP Involved in Pathogenesis-1) is a component of the conserved Pmk1/Mst12 signalling pathway—required for appressorium formation, penetration, and invasive growth. Global transcriptome analysis reveals that Bip1 and Mst12 regulate a common subset of genes, including effector genes, during pathogenesis. Furthermore, Bip1 is phosphorylated during plant infection, BIP1 expression is Mst12-dependent, and the two transcription factors also physically interact, consistent with heterodimer formation. These findings provide evidence that Mst12 is a master coordinator of pathogenesis-associated gene expression and is part of a hierarchy of co-ordinately controlled transcription factors deployed by M. oryzae during infection.