Identification of differentially expressed proteins in a mat1-2-deleted strain of Gibberella zeae, using a comparative proteomics analysis.

Gibberella zeae is a self-fertile ascomycetous fungus that causes important diseases of cereal crops. A comprehensive understanding of sexual reproduction in G. zeae is needed for disease control. To identify fungal proteins involved in this process, we compared the protein profiles of a wild-type strain and its self-sterile strain deleted for MAT1-2, a master regulator of sexual reproduction in G. zeae. Using 2-DE and either MALDI-TOF or ESI-Q-TOF MS, we identified 13 protein spots that showed statistically significant differences in expression levels between the two strains; 11 were reduced and two were increased in abundance in the DeltaMAT1-2 strain. Six of the 13 proteins were similar to those related to cell wall structure and the others were orthologs of proteins involved in metabolism or environmental stress responses. We confirmed that all the genes of the proteins examined were down-regulated during the sexual development stage in the DeltaMAT1-2, DeltaMAT1-1, and other strains deleted for a MAP kinase or a G-protein gene. These data suggest that differences in the protein expression levels are mostly affected by down-regulation of the corresponding genes in the DeltaMAT1-2 strain. To date, this is the first proteomics approach successfully identifying proteins differentially regulated by MAT1-2 in G. zeae.