Plasma membrane H+-ATPase, succinate and isocitrate dehydrogenases activities of vessel-associated cells in walnut trees
Plasma membrane H+-ATPase, succinate and isocitrate dehydrogenases activities of vessel-associated cells in walnut trees
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DOI：
10.1078/0176-1617-00503
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发表时间：
2001-10-01
影响因子：
4.3
通讯作者：
Lacointe, A
中科院分区：
文献类型：
--
作者：
Alves, G;Sauter, JJ;Lacointe, A
冬、春季核桃树维管液含糖量变化较大。导管相关细胞（Vessel-associated cells，VACs），又称接触细胞（contact cells），根据它们的位置，可以控制贮藏薄壁组织与木质部导管之间的营养交换。根据文献，树液的回收（流入）通过H（+）/糖共输在VAC/血管界面处发生，该共输取决于质膜H（+）-ATP酶产生的跨膜pH梯度。本研究的目的是调查ATP酶活性，使用灌注技术，允许使用几个效应物：羰基氰间氯苯腙（CCCP）和梭孢菌素（FC）。在冬季，解偶联剂CCCP揭示了木质部导管和导管相关细胞之间的低pH梯度。在这些条件下，FC，H（+）-ATP酶的激活剂，对灌注液的pH值没有影响，表明该酶可能是轻度活性。相比之下，接近萌芽，通过使用CCCP揭示了高pH梯度，并且在FC的存在下观察到灌注溶液的酸化。此外，细胞化学研究表明，位于线粒体的两个呼吸酶的高活性：NAD依赖的异柠檬酸脱氢酶和琥珀酸脱氢酶。假设在春季，VAC的这种高呼吸活性提供了可被质膜H（+）-ATP酶利用的有效ATP的相应增加。
In winter and spring, walnut trees exhibit variations of sugar content in the vascular sap. According to their location, the vessel-associated cells (VACs, also called contact cells) could control nutrient exchanges between the storage parenchyma and the xylem vessels. According to the literature, the recovery of sap (influx) occurs at the VAC/vessel interface via an H(+)/sugar symport that depends on the transmembrane pH gradient generated by the plasma membrane H(+)-ATPase. The aim of this study was to investigate the ATPase activity, using a perfusion technique that allows the use of several effectors: carbonyl cyanide m-chlorophenylhydrazone (CCCP) and fusicoccin (FC). During winter, the uncoupler CCCP revealed a low pH gradient between the xylem vessels and the vessel-associated cells. Under these conditions, FC, an activator of the H(+)-ATPase, had no effect on the pH of the perfusion solution, suggesting that the enzyme could be lightly active. In contrast, close to bud break, a high pH gradient was revealed by the use of CCCP, and an acidification of the perfusion solution was observed in the presence of FC. Moreover, cytochemical investigation showed high activity of two respiratory enzymes located in mitochondria: NAD-dependent isocitrate dehydrogenase and succinate dehydrogenase. The hypothesis is that in spring this high respiratory activity of VACs provides a consequent increase in available ATP that can be utilized by the plasma membrane H(+)-ATPase.