文摘
Under stress conditions, the mitochondrial respiratory chain generates reactive oxygen species that cause oxidative damage to lipids, proteins and nucleic acids. Mitochondrial chaperones are essential for repairing denatured proteins in plants confronted with diverse stresses. However, their functions have not been well characterized in lower plants such as bryophytes. Here, we cloned a heat-shock 70 protein gene (designated PnHSP70) from the Antarctic moss Pohlia nutans and investigated its transcription levels under stress conditions. The PnHSP70 cDNA encoded a polypeptide of 678 amino acids with an ATPase domain, a substrate peptide-binding domain and a C-terminal domain. Sequence alignment and phylogenetic analysis showed that PnHSP70 was homologous to other known mitochondrial HSP70 proteins. In addition, subcellular localization analysis in which the transient expression of PnHSP70-green fluorescent protein was observed in Arabidopsis thaliana mesophyll protoplasts revealed that PnHSP70 was targeted to mitochondria. Real-time PCR analysis showed that low or high temperature, salinity, drought or PEG treatments as well as UV-B radiation could induce up-regulation of PnHSP70 expression levels. The plant hormones abscisic acid and jasmonic acid also up-regulated the expression levels of PnHSP70. Together, our results revealed that PnHSP70, as a mitochondrial chaperone, might play an important role in the adaptation of the Antarctic moss P. nutans to the polar environment.