Cloning and sequence analysis of a serine protease gene from Rhizoctonia solani Kühn AG5.

The present study aimed to identify the subtilisin-like proteases (SLPs) of Rhizoctonia solani Kühn potentially involved in the virulence of this phytopathogenic fungus, which has 14 anastomosis groups (AGs) responsible for many crop diseases. Through mycelial microscope observation and strain identification of pathogenic fungus MS-3, it was determined to be R. solani AG-5. Both 5' and 3' rapid amplification of cDNA ends were used to clone the serine protease gene RsSLP from R. solani AG-5. The full-length obtained for RsSLP was 1714 bp with an open reading frame of 1587 bp, encoding a protein of 528 amino acids with a molecular mass of 55.8 kDa. This protein contained a predicted signal peptide for secretion but lacked a transmembrane domain or membrane anchor site. Bioinformatics analysis identified this protein as a serine protease with the Peptidase_S8 and Inhibitor_I9 characteristic domains of SLPs. Phylogenetic analysis suggested that frequent gene duplications of the SLPs occurred in R. solani (RsSLP), and RsSLP shares characteristic sequence features with virulence factors of other phytopathogenic fungi. Because the secretory serine protease RsSLP from R. solani AG5 is similar to the virulence factors of other phytopathogenic fungi, its identification will be helpful in studies considering the roles of these proteases in pathogen virulence.