Genome-wide analyses of DNA-binding proteins harboring AT-hook motifs and their functional roles in the rice blast pathogen, Magnaporthe oryzae

Transcriptional regulation is a complex process mediated by coordinated assembly complexes to ensure temporal and spatial gene expression. The AT-hook is a DNA-binding motif originally described in the high mobility group A of non-histone chromatin components. The AT-hook proteins bind to the minor groove of adenine-thymine (AT) rich regions of DNA and act as transcriptional cofactors coordinating nucleoproteins during transcriptional regulation. In this study, a genome-wide in silico analysis of AT-hook proteins was performed on the ascomycete plant pathogenic fungus, Magnaporthe oryzae. Quantitative real-time RT-PCR analysis revealed differential expression patterns of MoATH genes during development and plant infection. To increase our understanding of the functional role of AT-hook proteins in M. oryzae development and pathogenicity, a deletion mutant of MoATH10 was functionally characterized. Targeted deletion of MoATH10 significantly increased pigmentation and conidiation, indicating that MoATH10 is negatively involved in the regulation of pigmentation and conidiation in M. oryzae. Pathogenicity assays revealed that the Delta Moath10 mutant was less virulent. The reduced disease development of the Delta Moath10 mutant was due to a partial defect in invasive growth inside plant cells, but not appressorium-mediated penetration. These results suggest that MoATH10 is important for growth, development, and virulence in M. oryzae.