Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2010
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Soybean contains several bioactive peptides including leginsulin, a hormone-like peptide that plays a role in signal transduction. Leginsulin, a peptide made up of 37 amino acids, binds to soybean basic 7S globulin (43 kDa insulin receptor-like protein) and stimulates the protein kinase activity of the receptor protein. Leginsulin is homologous to pea albumin (PA1b) and belongs to the cysteine-knot family. Additionally, these bioactive peptides have also been shown to possess health-promoting effects. Even though the physiological function and tertiary structure of leginsulin have been explored, little is known about their distribution among soybean cultivars. Antibody generated against leginsulin was used to screen a diverse array of soybean accessions from the USDA Soybean Germplasm Collection to identify soybean cultivars that are rich in leginsulin. Analysis of 50% isopropanol-soluble proteins from 485 soybean lines by SDS-PAGE and Western blot analysis enabled the identification of 75 accessions that significantly accumulated leginsulin. Remarkably, all these accessions with the exception of two had their origin either from Japan, Korea or China. Leginsulin was barely detected in most of the commercial North American soybean cultivars used in this study. Western blot analysis revealed that the accumulation of leginsulin was mostly confined to the embryonic axis of some soybean cultivars (e.g. Williams 82) while in others (e.g. PI 458249) a significant amount of leginsulin was found both in the cotyledon and the embryonic axis. Examination of the soybean cultivar Williams 82 genome sequence revealed the presence of two homologous leginsulin genes (Gm13g26330 [leginsulin 1] and Gm13g26340 [leginsulin2]) on chromosome 13. We cloned the two leginsulin genes from PI 458249 and found them to be highly similar to that of Williams 82. Northern blot analysis indicated that leginsulin mRNA was abundant in Williams 82 embryonic axis but not in the cotyledon. In contrast, leginsulin mRNA was abundantly present in PI 458249, both in the embryonic axis and the cotyledons. Currently, we are examining the promoters and their cis-regulatory element composition within these genes to ascertain their role in the observed differential expression patterns.