Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/28/2010
Publication Date: 8/19/2010
Publication URL: http://hdl.handle.net/10113/49276
Citation: Chen, X., Wang, M.L., Holbrook Jr, C.C., Culbreath, A., Liang, X., Brennenman, T., Guo, B. 2010. Identification and characterization of a multigene family encoding germin-like proteins in cultivated peanut (Arachis hypogaea L.). Plant Molecular Biology Reporter. 29:389-403. Interpretive Summary: Peanut is one of the major economically-important legumes. On a global basis, peanut is a major source of protein and vegetable oil for human nutrition. However, peanut producers are facing many challenges such as a high cost of production due to chemical control of diseases in the U.S., and food safety concerns because of aflatoxin contamination. Peanut GLP (germin-like protein) genes have not yet been reported to be associated with an enzymatic activity that can be directly or indirectly related to peanut resistance to diseases. In this report, peanut AhGLP proteins associated with SOD (superoxide dismutase) activity may protect the E. coli cells from oxygen free radical mediated oxidative damage caused by the herbicide paraquat, resulting a better resistance to free radical toxicity. Further studies are needed to elucidate the roles of the peanut GLP family in plant cell growth and stress biology. In summary, this study provides information of the diverse nature of the peanut GLP family and suggests that some of AhGLPs might be involved in peanut disease resistance.
Technical Abstract: Germin-like proteins (GLPs) play diversified roles in plant development and defense response. Here, we identified 36 ESTs encoding GLPs from peanut (Arachis hypogaea L.). After assembly, these ESTs were integrated into eight unigenes, named AhGLP1 to AhGLP8, of which, three (AhGLP1-3) were comprised of 14, 10 and 7 EST clones, respectively, whereas the remaining ones were associated with one single clone. The length of the deduced amino acid (AA) residues ranged from 208 to 223 AAs except for AhGLP6 and AhGLP8, which were incomplete at the carboxyl terminus. All of the AhGLPs contained a possible N-terminal signal peptide that was 17 to 24 residues in length excluding AhGLP7, where there is likely a non-cleavable amino terminus. Phylogenetic analysis showed that these AhGLPs were classified into three subfamilies. Southern blot analysis indicated that AhGLP1 and AhGLP2 likely have multiple copies in the peanut genome. The recombinant mature AhGLP1 and AhGLP2 proteins were successfully expressed in Escherichia coli. The purified AhGLP2 has superoxide dismutase (SOD) activity in enzymatic assay, but not oxalate oxidase (OXO) activity. The SOD activity of AhGLP2 was stable up to 70' and resistant to hydrogen peroxide, suggesting that AhGLP2 might be a manganese-containing SOD. Furthermore, AhGLP2 could confer E. coli resistance to oxidative damage caused by paraquat, suggesting that the AhGLP2 likely protects peanut plants from reactive oxygen metabolites. Thus, information provided in this study indicates the diverse nature of the peanut GLP family and suggests that some of AhGLPs might be involved in plant defense response.