毛白杨幼苗低温锻炼过程中Ca^(2+)的作用及细胞Ca^(2+)-ATP酶活性的变化

Calcium Effect and Changes of Ca^(2+)-ATPase Activities During Chilling Hardening in Populus tomentosa Cuttings

观察了低温锻炼以及随后的常温生长中毛白杨幼苗质膜及线粒体Ca2 + ATP酶活性、CaM含量和抗冻性的变化。结果表明 ,单纯低温锻炼在一定程度上提高了毛白杨幼苗质膜及线粒体Ca2 + ATP酶活性、CaM含量和抗冻性 ,减小了低温胁迫所引起的质膜及线粒体Ca2 + ATP酶活性和CaM含量的下降程度 ,促进了胁迫后恢复过程中质膜及线粒体Ca2 + ATP酶活性和CaM水平的迅速回升。在低温锻炼的同时 ,用CaCl2 处理能加强低温锻炼的效果 ,但这种效应可被EGTA。

Populus tomentosa cuttings were established from dormant branches collected from Heilongjiang Province, China. To explore the role of calcium calmodulin messenger system in the transduction of low temperature signal in woody plants, P. tomentosa cuttings used for chilling hardening at -3℃ were pretreated with CaCl 2 (10 mmol/L), Ca 2+ chelator EGTA (3 mmol/L), Ca 2+ channel inhibitor LaCl 3 (100 μmol/L) or CaM antagonist CPZ (50 μmol/L). The changes in calmodulin (CaM) content, Ca 2+ ATPase activities of mitochondrial and plasma membrane, and LT 50 of cuttings were investigated to elucidate the physiological mechanisms by which trees adapt to chilling. The results showed that the content CaM, the Ca 2+ ATPase activities of mitochondrial and plasma membrane as well as chilling resistance of cuttings were increased by chilling hardening at -3℃ (Figs.1, 3 and 5; Table 1). Treatment with CaCl 2 at the time of chilling hardening enhanced the effect of chilling hardening and markedly increased the content of CaM, the Ca 2+ ATPase activities of mitochondrial and plasma membrane and the chilling resistance, but this enhancement was abolished by Ca 2+ chelator EGTA, Ca 2+ channel inhibitor LaCl 3 or CaM antagonist CPZ (Figs.1, 3 and 5; Table 1), indicating that the calcium calmodulin messenger system was involved in the course of chilling resistance formation. The leaves and branches of cuttings pretreated with CaCl 2 had increased by 39.15 and 48.74 μg/g FW of CaM content, by 24.12 and 37.25 μmol Pi mg -1 protein h -1 of Ca 2+ ATPase activities of plasma membrane, and by 15.48 and 21.56 μmol Pi mg -1 protein h -1 of Ca 2+ ATPase activities of mitochondrial membrane, respectively, as compared with chilling hardening (Figs.2, 4 and 6). In addition, LT 50 of cuttings was lowered from -14.3℃ in chilling hardening cuttings to -18.1℃ in the cuttings pretreated with CaCl 2 (Table 1). The addition of CaCl 2 at the same time of chilling hardening reduced the declining degree of CaM content, Ca 2+ ATPase activities of mitochondrial and plasma membrane caused by chilling stress at -14℃, and enhanced the increase level of CaM content and of Ca 2+ ATPase activity in the recovery periods (Figs.2, 4 and 6). Furthermore, the change in CaM content was closely correlated to the Ca 2+ ATPase activities of mitochondrial and plasma membrane, and correlated to the chilling resistance of cuttings after both chilling hardening with or without CaCl 2 pretreatment. It is suggested that the enhancement of chilling resistance of cuttings induced by chilling hardening be related to the effective activation of Ca 2+ ATPase activities of mitochondrial and plasma membrane. Ca 2+ calmodulin is involved in the regulation of the Ca 2+ ATPase activities of mitochondrial and plasma membrane, and the induction of chilling resistance of cuttings.