Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/29/2007
Publication Date: 6/1/2008
Citation: Janarthanan, S., Suresh, P., Radke, G., Morgan, T.D., Oppert, B.S. 2008. Arcelins from an Indian wild bean, Lablab purpureus, and insecticidal activity in storage pests. Journal of Agricultural Food Chemistry 56: 1676-1682. Interpretive Summary: Arcelins are insecticidal proteins in beans which have activity against some beetle pests. Arcelins from a wild Indian bean were isolated and characterized. Biochemical assays determined that this wild bean arcelin is very similar to its relative in other beans. Bioassays of 2% arcelin with several storage pests resulted in delayed larval development, and 5% doses resulted in complete mortality. Arcelins have the potential to control storage pests through the development of transgenic cereals containing arcelin genes.
Technical Abstract: Arcelin isoforms in the Indian wild bean, Lablab purpureus, were isolated from a crude seed homogenate by ion exchange and size exclusion chromatographies. The partially purified L. purpureus arcelin had haemagglutination and glycoslyation properties similar to arcelins isolated from other pulses. Data obtained from two dimensional gel electrophoresis, MALDI TOF and MALDI TOF/TOF, and N terminal protein sequencing of the isolated polypeptides indicate that arcelin from L. purpureus is similar to the arcelin 1, 2, and 6 allelic variants of Phaseolus vulgaris. Studies on the hydrolysis of proteins in the L. purpureus fraction by commercial proteases indicate that the L. purpureus arcelins are resistant to degradation by trypsin and chymotrypsin, moderately resistant to pepsin, but are readily hydrolyzed to smaller peptides by papain. Insect feeding bioassays with the storage pests Rhyzopertha dominica, an internal feeder, and Oryzaephilus surinamensis, an external feeder of grain demonstrated that L. purpureus arcelins at 2% resulted in retarded development, and a 5% dose resulted in complete mortality of all larvae. Our study has demonstrated that partially purified L. purpureus arcelin proteins function similar to arcelins from other pulses and have the potential to control storage pests in cereals transformed with L. purpureus arcelin genes.