MoSwi6, an APSES family transcription factor, interacts with MoMps1 and is required for hyphal and conidial morphogenesis, appressorial function and pathogenicity of Magnaporthe oryzae

The Magnaporthe oryzae mitogen-activated protein kinase (MAPK) MoMps1 plays a critical role in the regulation of various developmental processes, including cell wall integrity, stress responses and pathogenicity. To identify potential effectors of MoMps1, we characterized the function of MoSwi6, a homologue of Saccharomyces cerevisiae Swi6 downstream of MAPK Slt2 signalling. MoSwi6 interacted with MoMps1 both in vivo and in vitro, suggesting a possible functional link analogous to Swi6Slt2 in S. cerevisiae. Targeted gene disruption of MoSWI6 resulted in multiple developmental defects, including reduced hyphal growth, abnormal formation of conidia and appressoria, and impaired appressorium function. The reduction in appressorial turgor pressure also contributed to an attenuation of pathogenicity. The ?Moswi6 mutant also displayed a defect in cell wall integrity, was hypersensitive to oxidative stress, and showed a significant reduction in transcription and activity of extracellular enzymes, including peroxidases and laccases. Collectively, these roles are similar to those of MoMps1, confirming that MoSwi6 functions in the MoMps1 pathway to govern growth, development and full pathogenicity.