Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/18/2008
Publication Date: 7/15/2008
Citation: Chen, X.; Brenneman, T.; Culbreath, A.; Holbrook Jr., C.; Guo, B. 2008. Characterization of two peanut oxalate oxidase genes and development of peanut cultivars resistant to stem rot (Sclerotium rolfsii)[abstract]. Proceedings of the American Phytopathological Society meeting, July 26-30, 2009 Minneapolis, MN.
Technical Abstract: In the southeastern U.S., stem rot (Sclerotium rolfsii) is a common and destructive disease of peanut. Research has suggested the enhancement of resistance to Sclerotinia minor in peanut by expressing a barley oxalate oxidase gene. Oxalate oxidase belongs to the germin family of proteins and acts as a source of hydrogen peroxide (H2O2) in certain plant-pathogen interactions. We have identified and cloned two peanut endogenous oxalate oxidase genes, AhOxOl, originating from peanut leaf libraries, and AhOxOs from seed libraries. The goal is to characterize these two genes in resistance to S. rolfsii. The AhOxOl including 991 bp cDNA sequence encodes a 219 amino acid protein with a 21-residue signal peptide. After cleavage of the signal peptide, it has a mass of 20.84 kDa. The AhOxOs comprised of 744 bp cDNA encodes a protein with 220 amino acid residues containing a putative signal peptide of 24 residues, with a mass of 20.63 kDa after removal of the signal peptide. The two proteins both contain three motifs, Q/NDL/FCVAD, G(X)5HXH(X) 11G and G(X)5P(X) 4H(X) 3N, which are characteristic to germin-like proteins. Furthermore, the deduced protein of AhOxOl consists of the “germin box” (HI/THPRATEI), which is a conserved sequence shared by germins within the motif G(X)5HXH(X) 11G. Searches of GenBank database indicate that AhOxOl and AhOxOs, with approximately 37% of amino acid similarity to each other, exhibit respectively up to 76% and 82% amino acid identity to certain plant germin-like proteins. Southern blot analysis showed that the two genes possibly exist in at least four copies in the peanut genome. Northern blots conducted with total RNA from seed and leaf tissues of resistant and susceptible genotypes indicated that AhOxOs is mainly expressed in peanut seed. Further functional characterization will be conducted.