Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 15, 2003
Publication Date: December 15, 2003
Citation: Liang, X.Q., Guo, B.Z., Holbrook, C.C., Lynch, R.E. 2003. Differential induction of antifungal protein chitinase and (Beta)-1-3-Glucanase by Aspergillus flavus in different peanut lines [abstract]. In: Proceedings of the 3rd Fungal Genomics, 4th Fumonisin, and 16th Aflatoxin Elimination Workshops, October 13-15, 2003, Savannah, Georgia. p. 59. Technical Abstract: Chitinase and ß-1-3-glucanase are believed to be important PR-proteins in defending plants against pathogens. They can protect plants from fungal infection by their direct lystic action on fungal cell wall or by releasing oligosaccharide signal molecules that can activate a variety of plant defenses. The differential expressions of chitinase and ß-1-3-glucanase in response to infection by Aspergillus flavus were evaluated in mature kernels of both resistant and susceptible peanut genotypes. The increase of endo-chitinase activity was found after treating the seeds with A. flavus in both resistant and susceptible genotypes. The enzyme activity was considerably higher (4 fold) in the resistant genotypes at 3-4th day after inoculation, but 3-fold in susceptible genotypes. No significant differences in the activities of exo-chitinase were observed in either resistant or susceptible genotypes. A. flavus inoculation led to an increase of ß-1-3-glucanase activity in both resistant and susceptible genotypes. The ß-1-3-glucanase activity doubled at 1st, and was 10-fold at 5th day in resistant genotypes after inoculation, but it was significantly lower in susceptible genotypes. In native PAGE (polyacrylamide gel electrophoresis), one band corresponding to endo-chitinase isoforms was detected in both susceptible and resistant genotypes. But the new band occurred in resistant genotypes at 1st day after inoculation, while at 3rd day in susceptible genotypes. The isoform patterns of ß-1-3-glucanase showed that 8 new isoform bands were detected in resistant genotypes after inoculation, with 5 bands in susceptible genotypes. The new bands corresponding to ß-1-3-glucanase were tested at 1st day after inoculation in resistant genotype, while at 4th day in susceptible genotype. Chitinase in Yueyou 20 seed treated by A. flavus was purified by precipitation with ammonium sulfate at a saturation of 60% followed by affinity chromatography on a column of regenerated chitin. The purified enzyme showed single band on SDS-PAGE and the molecular weight was estimated as 31 kDa. The purified chitinase can significantly inhibit spores germination and hypha extending of A. flavus in vitro. The results implied that the two hydrolyses play an important role in resistance to A. flavus infection in peanut seeds.