Two conidiation-related Zn(II)2Cys6 transcription factor genes in the rice blast fungus.

Regulation of gene expression by transcription factors (TFs) helps plant pathogens to interact with the host plants and to sustain a pathogenic lifestyle in the environmental changes. Elucidating novel functions of TFs is, therefore, crucial for understanding pathogenesis mechanisms of plant pathogens. Magnaporthe oryzae, the rice blast pathogen, undergoes a series of developmental morphogenesis to complete its infection cycle. To understand TF genes implicated in pathogenic development of this fungus, two Zn(II)2Cys6 TF genes, MoCOD1 and MoCOD2, whose expression was notably induced during conidiation, were functionally characterized. Targeted deletion of MoCOD1 resulted in defects in conidiation and pathogenicity due to defects in appressorium formation and invasive growth within the host cells. MoCOD2 was also a critical regulator in conidiation and pathogenicity, but not in conidial germination and appressorium formation. When rice plants were inoculated with conidia of the ΔMocod2 mutant, rapid accumulation of dark brown granules was observed around the infection sites in the plant cells and no visible disease symptom was incited. Taken together, both MoCOD1 and MoCOD2 play important roles in conidiation and pathogenicity of the rice blast fungus.