Molecular characterization of three hypersensitive-induced reaction genes that respond to Phytophthora sojae infection in Glycine max L. Merr.

Hypersensitive-induced reaction (HIR) proteins, which are members of the proliferation, ion and death (PID) superfamily, have been shown to be involved in the defense responses of several plant species. In this study, three HIR-like genes from soybean, designated as GmHIR1, GmHIR3 and GmHIR4, were cloned and characterized. They each contained four introns and five exons and shared conservative structure of genomic organization. The deduced polypeptide sequences of GmHIRs share high degrees of similarity with HIR proteins of other species. However, QRT-PCR analysis indicated that the expression levels in different tissues were not the identical. The expression of GmHIRs were rapidly induced by Phytophthora sojae infection in the resistant genotype, while induction was very weak in the susceptible genotype. In addition, the expression of these genes were also repressed by hydrogen peroxide (H2O2) treatment. Promoter analysis indicates that several defenseresponsive elements are present in the GmHIR promoter. To our knowledge, this is the first report on molecular cloning and initial characterization of HIR-like genes in soybean. This study may help elucidate soybean disease resistance, which would enhance efforts to control soybean Phytophthora root and stem rot disease