Effect of LiCl on phosphoenolpyruvate carboxylase kinase and the phosphorylation of phosphoenolpyruvate carboxylase in leaf disks and leaves of Sorghum vulgare
Effect of LiCl on phosphoenolpyruvate carboxylase kinase and the phosphorylation of phosphoenolpyruvate carboxylase in leaf disks and leaves of Sorghum vulgare
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DOI：
10.1007/s00425-006-0391-0
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发表时间：
2007-03-01
期刊：
影响因子：
4.3
通讯作者：
Garcia-Maurino, Sofia
中科院分区：
文献类型：
--
作者：
Antonio Monreal, Jose;Javier Lopez-Baena, Francisco;Garcia-Maurino, Sofia
在目前的工作中，我们在 C-4 植物高粱的光照叶盘和叶子中研究了 LiCl 对磷酸烯醇丙酮酸羧化酶激酶 (PEPCase-k)、C-4 磷酸烯醇丙酮酸羧化酶 (PEPCase: EC 4.1.1.31) 及其磷酸化过程的影响。尽管这种盐对老叶造成严重损害，但它并没有显着改变幼叶的生理参数（光合作用、蒸腾速率、细胞间二氧化碳浓度）。使用免疫学方法证明 PEPCase-k 蛋白在光照叶组织中快速积累，与其催化活性的增加一致。在体内，LiCl 可强烈增强光对 PEPCase-k 蛋白质含量的影响，该过程依赖于蛋白质合成。与此形成鲜明对比的是，在重构测定中发现盐抑制 PEPCase-k 活性，并降低 LiCl 处理植物中的 C-4 PEPCase 含量和磷酸化状态。短期（15 分钟）LiCl 处理增加了 IP3 水平、PPCK 基因表达和 PEPCase-k 积累。延长处理时间（1 小时）显着降低了 IP3 和 PPCK 基因表达，同时 PEPCase-k 活性保持较高水平。胞质蛋白合成抑制剂放线菌酮 (CHX) 可以阻断对照植物中激酶的光依赖性上调，但在预光照、氯化锂处理的叶子中，发现该过程对这一过程没有活性。这表明盐可能通过减少相应多肽的降解而导致激酶周转发生改变。总而言之，这些结果确立了 PEPCase-k 和 PEPCase 磷酸化作为高等植物中的锂靶点，并且这种盐可以提供一种方法来进一步研究控制两种酶活性的级联的组织和功能。
In the present work, the effect of LiCl on phosphoenolpyruvate carboxylase kinase (PEPCase-k), C-4 phosphoenolpyruvate carboxylase (PEPCase: EC 4.1.1.31) and its phosphorylation process has been investigated in illuminated leaf disks and leaves of the C-4 plant Sorghum vulgare. Although this salt induced severe damages to older leaves, it did not significantly alter the physiological parameters (photosynthesis, transpiration rate, intercellular CO2 concentration) of young leaves. An immunological approach was used to demonstrate that the PEPCase-k protein accumulated rapidly in illuminated leaf tissues, consistent with the increase in its catalytic activity. In vivo, LiCl was shown to strongly enhance the light effect on PEPCase-k protein content, this process being dependent on protein synthesis. In marked contrast, the salt was found to inhibit the PEPCase-k activity in reconstituted assays and to decrease the C-4 PEPCase content and phosphorylation state in LiCl treated plants. Short-term (15 min) LiCl treatment increased IP3 levels, PPCK gene expression, and PEPCase-k accumulation. Extending the treatment (1 h) markedly decreased IP3 and PPCK gene expression, while PEPCase-k activity was kept high. The cytosolic protein synthesis inhibitor cycloheximide (CHX), which blocked the light-dependent up-regulation of the kinase in control plants, was found not to be active on this process in preilluminated, LiCl-treated leaves. This suggested that the salt causes the kinase turnover to be altered, presumably by decreasing degradation of the corresponding polypeptide. Taken together, these results establish PEPCase-k and PEPCase phosphorylation as lithium targets in higher plants and that this salt can provide a means to investigate further the organization and functioning of the cascade controlling the activity of both enzymes.