Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 2009
Publication Date: January 15, 2010
Citation: Xie, Y.-R., Chen, Z.-Y., Brown, R.L., Bhatnagar, D. 2010. Expression and Functional Characterization of two Pathogenesis-Related Protein 10 Genes from Zea mays. Journal of Plant Physiology. 167(2):121-130. Interpretive Summary: The fungus named Aspergillus flavus produces a poison called aflatoxin when it infects corn kernels. Aflatoxin prevents the corn from being used commercially. The best strategy for controlling this problem is to develop corn that is resistant to aflatoxin contamination. Towards this aim, we isolated and identified through comparisons of resistant with susceptible corn lines, proteins that are produced in relatively higher amounts in the resistant lines. One of these proteins, previously identified, is called ZMPR10 and it has shown ability to inhibit fungal growth and to destroy fungal RNA. In order to learn more about the function of PR-10 proteins in resistance, another PR-10 (ZMPR10.1), also isolated from corn, was compared to the former. Both proteins increased in amount when corn tissue was either put under environmental stress or came in contact with microorganisms like Aspergillus flavus. ZMPR10, however, was expressed in corn tissues at higher levels than ZMPR10.1. This study indicates that these proteins may be important to resistance. Further studies may determine them to be useful to breeders as markers for transferring resistance to develop aflatoxin-resistant commercial corn. This could lead to future savings of millions of dollars to growers, as a result of the elimination of aflatoxin contamination of corn.
Technical Abstract: Pathogenesis-related protein 10 (PR10) is one of seventeen PR protein families and plays important roles in plant response to biotic and abiotic stresses. A novel PR10 gene (ZmPR10.1), which shares 89.8% and 85.7% identity to the previous ZmPR10 at the nucleotide and amino acid sequence level, respectively, was isolated from maize. ZmPR10 and ZmPR10.1 were mainly expressed in root tissues with low expression in other tissues. ZmPR10.1 had significantly lower expression than ZmPR10 in all tissues examined. The expression of both ZmPR10 and ZmPR10.1 was induced by most abiotic stresses including SA, CuCl2, H2O2, coldness, darkness and wounding during the 16-h treatments, and biotic stresses such as Erwinia stewartii and Aspergillus flavus infection. Different patterns of responses between ZmPR10 and ZmPR10.1 were observed when treated with NAA and Erwinia chrysanthemi. Both ZmPR10.1 and ZmPR10 showed RNase activity in vitro with an optimal pH and temperature of 6.5 and 55 ºC. Their RNase activities were significantly inhibited by low concentrations (1.0 mM) of Cu2+, Ag+, Co2+, SDS, EDTA or DTT. However, ZmPR10.1 possessed significantly higher (8-fold) specific activity than ZmPR10. Also, ZmPR10.1 showed a stronger inhibition against bacterium Pseudomonas syringae pv. tomato DC3000 in vivo and fungus A. flavus in vitro than ZmPR10, which indicates its potential important role in host plant defense.