Expression and functional characterization of two pathogenesis-related protein 10 genes from Zea mays.

A novel PR10 gene (ZmPR10.1) was isolated from maize and its expression and function were compared with the previous ZmPR10. ZmPR10.1 shares 89.8% and 85.7% identity to ZmPR10 at the nucleotide and amino acid sequence level, respectively. ZmPR10 and ZmPR10.1 were mainly expressed in root tissue 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, CuCl(2), H(2)O(2), coldness, darkness and wounding during the 16-h treatments, and biotic stresses such as Erwinia stewartii and Aspergillus flavus infection. However, ZmPR10.1 was induced only 2 HAT and down-regulated thereafter, whereas ZmPR10 remained induced during the 16-h NAA treatment. Also, inoculation with Erwinia chrysanthemi caused about 2-fold induction in ZmPR10.1 expression 60 HAT but not significant changes for ZmPR10. Both ZmPR10.1 and ZmPR10 showed RNase activity in vitro with an optimal pH and temperature of 6.5 and 55 degrees C. Their RNase activities were significantly inhibited by low concentrations (1.0mM) of Cu(2+), Ag(+), Co(2+), SDS, EDTA or DTT. However, ZmPR10.1 possessed significantly higher (8-fold) specific RNase 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, indicating that ZmPR10.1 may also play an important role in host plant defense.