A Subtilisin-like Protein from Soybean Induces Expression of Defense-related Genes

Attack by herbivores and pathogens activate the release of plant compounds that exhibit defense responses. Among those compounds are small peptides, which are short polymers of amino acids joined by peptide bonds. However, only a few of these defense peptides have been identified and reported. Thus, Gregory Pearce and colleagues at Washington State University isolated a peptide from soybean leaves that even nanomolar concentrations have induced pH of soybean (Glycine max) suspension media in a period of 10 minutes. This is a similar response with other pathogen-derived signal molecules. When they sequenced the amino acid of the peptide, they found that it is derived from a member of the subtilisin-like protease (subtilase) family, which are characterized by a catalytic triad of amino acids-aspartate, histidine, and serine. The researchers named this peptide signal as Glycine max Subtilase Peptide (GmSubPep). When GmSubPep is supplied to soybean cultures, it was found to induce the expression of defense genes. Thus, this study confirms that GmSubPep is a plant defense peptide signal embedded within a plant protein with specific metabolic function, and provides hints about plant defense mechanisms.

Read the complete research article released by PNAS at http://www.pnas.org/content/107/33/14921.full.