Secretion Property and Gene Expression Pattern of a Putative Feruloyl Esterase in Magnaporthe grisea

Plant cell walls are a pivotal battleground between microbial pathogens and their plant hosts. Microbial pathogens secrete an array of cell-wall-degrading enzymes to depolymerize the noncellulosic polysaccharides of primary cell walls, which are essential for the vitality of pathogens, either saprophytically, pathogenetically or both. The predicted protein encoded by MGG_01403.5 from Magnaporthe grisea has a high degree of sequence identity with the ferulic acid esterase A (so to be designated as MgFaeA) from Penicillium funiculosum. Tested by the SignalP, TMHMM and Protcomp programs, the 284-amino acid hypothetical protein contained a cleavable signal peptide at the N terminus, lacked transmembrane structure, and appeared located in the extracellular matrix. In the work presented here, MgFaeA, with a His6 tag at its C-terminus, was introduced into M. grisea for overexpression. The MgFaeA-His6 fusion protein was purified from the culture filtrate, which confirmed the secretion property of MgFaeA in the fungus. To further investigate the role of MgFaeA on rice infection, RT-PCR was used to analyze the gene expression during different stages of infection. The results indicated that MgFaeA transcripts were detectable as early as 72 hpi, and reached to peak at 7 dpi. It suggested that the MgFaeA gene might be involved in the fungal pathogenesis.