| The young grape plants (Vitis vinifera L. cv. Jingxiu) were used as experimental materials to study on the mechanisms of cold-resistance induced by heat acclimation (HA) or heat-tolerance induced by cold acclimation (CA), and probe the mechanisms of cross adaptation to the temperature stresses in grape plants. The results obtained were as following.The ultrastructural characteristics of mesophyll cell in chilling-treated plants after HA and heat-treated plants after CA were observed and compared using the transmission electron microscopy, slight injury appeared in ultrastructure of mesophyll cell after either HA (38℃/10 h) or CA (8℃/2.5 d), but the tolerance to subsequent extreme temperature stress was remarkably improved by HA or CA pretreatment. The mesophyll cells of non-HA pretreated plants were remarkably damaged under cold stress, principally appeared in the chloroplast, mitochondria, nucleus and plasmolemma. Similarly, CA pretreatment could protect chloroplast, mitochondria and nucleus against subsequent heat stress, and thus the thermo-resistance of grape plants was improved. The obtained results, to our knowledge, firstly offered the cytological evidence of cross-adaptation to temperature stresses in grape plants.The changes in activities of microsomal membrane H+-ATPase and Ca2+-ATPase in chilling-treated plants after HA and heat-treated plants after CA were analyzed with biochemistry assay and electromicroscopic-cytochemical assay in which cerium trichloride (CeCl3) precipitation method was adopted. The results showed that the plasma membrane H+-ATPase and Ca2+-ATPase activities were increased by HA or CA pretreatments. There were no obvious changes in V- and F-type H+-ATPase and tonoplast Ca2+-ATPase activities after HA or CA. However, the stability of all types of ATPase activities was enhanced under the following cross-temperature-stresses, and the activities were always higher than that of control. Western-blotting assay of plasma membrane H+-ATPase (P-H+-ATPase) detected a 54kDa peptide of which the immuno-signal intensity was stronger in HA or CA pretreated plants than that in control before or after stress. This result was consistent with the biochemistry assay and electromicroscopic-cytochemical assay. So it is considered that the higher P-H+-ATPase activity induced by HA or CA was partly attributed to the increase of the enzyme amounts.The activity of cell antioxidant enzymes such as catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were gradually decreased, but the O2- generation rate and H2O2 content, relative conductivity and MDA content were rapidly increased. However, in HA plants, the O2- generation rate and H2O2 content increased to a certain degree and then decreased, the relative conductivity and MDA concentration maintained relative lower level than those in control plants under cold stress. It is important that, the change tendency of all those indexes in CA plants under heat stress was consistent with that in HA plants under cold stress. These results presented here suggested that a similar antioxidant mechanism was involved in the chilling resistance induced by HA and heat tolerance induced by CA.Subcellular localization of HSP70 and sHSP17.6 in mesophyll cell of chilling-treated plants afterHA and of heat-treated plants after CA were studied with immuno-gold electron microscopic technique. The results showed that HSP70 was mainly located in the chloroplast, starch granules, mitochondria, nucleus and cytoplasm. The distribution of sHSP17.6 in mesophyll cell was similar to that of HSP70, but there was no immuno-gold labeling of sHSP17.6 in the starch granules. The gold particles density of labeling sHSP17.6 was fewer than HSP70. The immuno-signal intensity of two HSPs especially of sHSP17.6 was increased after HA, and remained much stronger in HA plants than that in control ones during cold stress. There were no obvious changes in the amounts of two HSPs between CA plants and control ones. However, the expression of two HSPs was significantly induced by CA during heat str...
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