Genome-wide identification of small heat-shock protein (HSP20) gene family in grape and expression profile during berry development.

BACKGROUND: Studies have shown that HSP20 (heat-shock protein 20) genes play important roles in regulating plant growth, development, and stress response. However, the grape HSP20 gene family has not been well studied. RESULTS: A total of 48 VvHSP20 genes were identified from the grape genome, which were divided into 11 subfamilies (CI, CII, CIII, CV, CVI, CVII, MI, MII, ER, CP and PX/Po) based on a phylogenetic analysis and subcellular localization. Further structural analysis showed that most of the VvHSP20 genes (93.8%) had no intron or only one intron, while genes that clustered together based on a phylogenetic tree had similar motifs and evolutionarily conserved structures. The HSP20s share a conservedα-crystalline domain (ACD) and the different components of the ACD domain suggest the functional diversity of VvHSP20s. In addition, the 48 VvHSP20 genes were distributed on 12 grape chromosomes and the majority of VvHSP20 genes were located at the proximal or distal ends of chromosomes. Chromosome mapping indicated that four groups of VvHSP20 genes were identified as tandem duplication genes. Phytohormone responsive, abiotic and biotic stress-responsive, and plant development-related cis-elements were identified from the cis-regulatory elements analysis of VvHSP20s. The expression profiles of VvHSP20s genes (VvHSP20-1, 11, 14, 17, 18, 19, 20, 24, 25, 28, 31, 39, 42, and 43) were largely similar between RNA-Seq and qRT-PCR analysis after hydrogen peroxide (H2O2) treatment. The results showed that most VvHSP20s were down-regulated by H2O2 treatment during fruit development. VvHSP20s genes were indeed found to be involved in the grape berry development and differences in their transcriptional levels may be the result of functional differentiation during evolution. CONCLUSIONS: Our results provide valuable information on the evolutionary relationship of genes in the VvHSP20 family, which is useful for future studies on the functional characteristics of VvHSP20 genes in grape.

Heat shock protein 20 interacting with phosphorylated Akt reduces doxorubicin-triggered oxidative stress and cardiotoxicity.

Doxorubicin (DOX) is a widely used antitumor drug, but its application is limited because of its cardiotoxic side effects. Heat shock protein (Hsp)20 has been recently shown to protect cardiomyocytes against apoptosis, induced by ischemia/reperfusion injury or by prolonged beta-agonist stimulation. However, it is not clear whether Hsp20 would exert similar protective effects against DOX-induced cardiac injury. Actually, DOX treatment was associated with downregulation of Hsp20 in the heart. To elucidate the role of Hsp20 in DOX-triggered cardiac toxicity, Hsp20 was first overexpressed ex vivo by adenovirus-mediated gene delivery. Increased Hsp20 levels conferred higher resistance to DOX-induced cell death, compared to green fluorescent protein control. Furthermore, cardiac-specific overexpression of Hsp20 in vivo significantly ameliorated acute DOX-triggered cardiomyocyte apoptosis and animal mortality. Hsp20 transgenic mice also showed improved cardiac function and prolonged survival after chronic administration of DOX. The mechanisms underlying these beneficial effects were associated with preserved Akt phosphorylation/activity and attenuation of DOX-induced oxidative stress. Coimmunoprecipitation studies revealed an interaction between Hsp20 and phosphorylated Akt. Accordingly, BAD phosphorylation was preserved, and cleaved caspase-3 was decreased in DOX-treated Hsp20 transgenic hearts, consistent with the antiapoptotic effects of Hsp20. Parallel ex vivo experiments showed that either infection with a dominant-negative Akt adenovirus or preincubation of cardiomyocytes with the phosphatidylinositol 3-kinase inhibitors significantly attenuated the protective effects of Hsp20. Taken together, our findings indicate that overexpression of Hsp20 inhibits DOX-triggered cardiac injury, and these beneficial effects appear to be dependent on Akt activation. Thus, Hsp20 may constitute a new therapeutic target in ameliorating the cardiotoxic effects of DOX treatment in cancer patients.