Isolation and characterization of a new defense gene from soybean

A cDNA clone of a single-copy gene designated SbPRP was isolated and characterized from 2-week-old soybean seedlings. It putatively encodes a bimodular protein similar to developmentally regulated proteins in other plant species. The deduced amino acid sequence consists of 126 amino acids with a distinct proline-rich domain (17 amino acids) and a long hydrophobically cysteine-rich domain (84 amino acids), plus a signal peptide of 25 amino acids in N terminal. SbPRP mRNA transcripts accumulated in an organ specific manner. It can be detected in leaves and epicotyls of soybean seedlings, whereas virtually expression signal of SbPRP was not detected in cotyledons, hypocotyls and roots. Further Northern hybridization suggested that SbPRP steady-state mRNA level accumulated differentially not only in response to salicylic acid, but to the inoculation of soybean mosaic virus Sa strain. Also it was responsive to drought treatment and salt (NaCl) stress. Therefore it is likely that SbPRP functions as a defense gene in soybean.