Expression and function analysis of a rice OsHSP40 gene under salt stress.

Heat shock proteins (HSPs) play essential roles in both plant growth and abiotic stress tolerance. In rice, OsHSP40 was recently reported to regulate programmed cell death (PCD) of suspension cells under high temperature. However, the expression and functions of OsHSP40 under normal growth or other abiotic stress conditions is still unknown. We reported the expression and function of a rice OsHSP40 gene under salt stress. Homologous proteins of OsHSP40 were collected from the NCBI database and constructed the neighbor-joining (NJ) phylogenetic tree. The expression pattern of OsHSP40 was detected by qRT-PCR under NaCl (150 mM) treatment. Then, identified a rice T-DNA insertion mutant oshsp40. At last, we compared and analyzed the phenotypes of oshsp40 and wild type under salt stress. OsHSP40 was a constitutively expressed small HSP (sHSP) gene and was close related to other plant sHSPs. Moreover, the expression of OsHSP40 was regulated by salt, varying across time points and tissues. Furthermore, the growth of T-DNA insertion mutant of OsHSP40 (designated as oshsp40) was suppressed by NaCl (150 mM) compared with that of the WT at seedling stage. Detailed measurement showed root and shoot length of the oshsp40 seedlings were significantly shorter than those of the WT seedlings under NaCl stress. In addition, the pot experiment results revealed that seedlings of oshsp40 withered more seriously compared with those of WT after NaCl treatment and recovery, and that survival rate and fresh weight of oshsp40 seedlings were significantly reduced. Taken together, these data suggested that OsHSP40 had multiple functions in rice normal growth and abiotic stress tolerance.