The role of the Tra1p transcription factor of Magnaporthe oryzae in spore adhesion and pathogenic development.

Transcription factors play a critical regulatory role in development by binding DNA and initiating alterations in gene transcription. The transcript of the putative Magnaporthe oryzae transcription factor-encoding gene TRA1 accumulates during germination and this accumulation was previously found to depend on the transcription factor Con7p. In the current work tra1⁻ mutants were generated and these strains were found to exhibit a reduced attachment, germination, appressorium formation and virulence.

The Magnaporthe grisea class VII chitin synthase is required for normal appressorial development and function.

The plant pathogenic fungus Magnaporthe grisea is able to enter its host via appressorium-mediated penetration. Earlier investigations have shown that these infection structures are rich in the cell wall polysaccharide chitin. Previously, we have described how the transcription of a class VII chitin synthase-encoding gene CHS7 is completely dependent on the putative transcription factor Con7p during the germination of conidia, and how con7(-) mutants are unable to form appressoria under any conditions tested.

The transcription factor Con7p is a central regulator of infection-related morphogenesis in the rice blast fungus Magnaporthe grisea.

A strain harbouring an insertion within the promoter of the CON7 gene of Magnaporthe grisea was isolated. This gene was previously shown to be essential for appressorium formation and growth in planta and is predicted to encode a transcription factor. Microarray-based gene expression analysis was used to identify several genes whose transcription during germination depends on Con7p.