Accumulation and subcellular localization of heat shock proteins in young grape leaves during cross-adaptation to temperature stresses

A number of high abundant heat shock proteins (HSPs) could be synthesized under stress conditions. In this study, the role of HSP70 and sHSP17.6 in the cross-adaptation induced by either heat acclimation (HA) or cold acclimation (CA) was investigated in the leaves from annual young grape plants (Vitis vinifera L. cv. Jingxiu). The subcellular localizations of HSP70 and sHSP17.6 within mesophyll cells were observed using immuno-gold electron microscopic technique. HSP70 was distributed predominantly in the chloroplast, starch granules, mitochondria, nucleus and cytoplasm. The distribution pattern of sHSP17.6 in mesophyll cells was similar partly to HSP70, except the density of gold particles labeling sHSP17.6 was lower than that of HSP70. HA- or CA-pretreatment only change the amount accumulation of HSP70 and sHSP17.6 proteins, the regional distribution of these two HSPs in mesophyll, however, remained unaltered. Moreover, the results from immuno-blotting study were in agreement with subcellular distribution, indicated the amounts of two HSPs especially of sHSP17.6 were increased both in HA- and CA-pretreated plants during temperature stresses. The synthesis of HSPs paralleled to the increase of cold tolerance or heat resistance. These data indicated that HSP70 and sHSP17.6 might play a crucial role in the development of cross-adaptation to temperature stress induced by HA- or CA-pretreatment in grape plants. In addition, the experiments using mRNA transcription inhibitor (actidione D) or protein synthesis inhibitor (cycloheximide) demonstrated the accumulation of two HSPs by HA was controlled at both transcriptional and translational levels.