Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 28, 2005
Publication Date: April 1, 2006
Citation: Guo, B., Holbrook, Jr., C.C., Liang, X. 2006. Peanut PR protein, B-1,3-glucanase, induction by Aspergillus flavus and copurification with a conglutin-like protein [abstract]. Proceedings of the 18th Annual Multi-Crop Aflatoxin Elimination Workshop, October 24-26, 2005, Raleigh, NC. p. 87. Technical Abstract: Aflatoxin contamination of peanut has been identified as the most important health problem facing the peanut industry. Infection of peanut (Arachis hypogaea L.) seeds by Aspergillus flavus and A. parasiticus is a serious problem that can result in aflatoxin contamination in the seeds. Breeding resistant cultivars would be an effective approach to reduce aflatoxin accumulation. The objective of this study was to investigate the expression of pathogenesis-related (PR) protein B-1,3-glucanase and the isoform patterns in peanut seeds inoculated with A. flavus. Peanut genotypes, GT-C9 and GT-C20 (both resistant to Aspergillus flavus infection), and Georgia Green and A100 (both susceptible to A. flavus infection), were used in this study. The activities of B-1,3-glucanase were similar in the un-infected seeds of all genotypes, but increased significantly in the resistant genotypes after inoculation in comparison with the susceptible genotypes. An in-gel (native PAGE) enzymatic activity assay of B-1,3-glucanase revealed that there were more protein bands corresponding to B-1,3-glucanase isoforms in the infected seeds of resistant genotypes than in the infected seeds of susceptible genotypes. Both acidic and basic B-1,3-glucanase isoforms were detected in the IEF gel. Thin layer chromatography (TLC) analysis of the hydrolytic products from the reaction mixtures of the substrate with the total protein extract or individual band of native PAGE revealed the presence of enzymatic hydrolytic oligomer products. The individual bands corresponding to the bands of B-1,3-glucanase isoforms Glu 1-5 were separated on the SDS-PAGE resulting in two bands, 10-kDa and 13-kDa, respectively. The sequence of the 13-kDa major protein band showed a high degree of homology to conglutin, a storage protein in peanut seeds. Conglutin is reported as a peanut allergen, Ara h2, and has trypsin inhibitor function. Our data provide the first evidences for peanut having B-1,3-glucanase activities and the association with the resistance to A. flavus colonization in peanut seeds.