Phosphorylation of soybean nodulin 26 on serine 262 enhances water permeability and is regulated developmentally and by osmotic signals
Phosphorylation of soybean nodulin 26 on serine 262 enhances water permeability and is regulated developmentally and by osmotic signals
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DOI：
10.1105/tpc.009787
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发表时间：
2003-04-01
期刊：
影响因子：
11.6
通讯作者：
Roberts, DM
中科院分区：
文献类型：
--
作者：
Guenther, JF;Chanmanivone, N;Roberts, DM
大豆根瘤蛋白26被表达并靶向固氮根瘤的共生体膜，在那里形成一个具有适度水分运输速率的水孔蛋白通道。在这项研究中，我们证明了在共生体相关的钙依赖蛋白激酶的催化下，Ser-262上的结节蛋白26的磷酸化刺激了其固有的水传输速率。此外，利用一种磷酸化特异性抗体，我们已经阐明了在活体中结节蛋白26磷酸化的发育外观和调节。虽然首先在分化的感染细胞中检测到结节蛋白26蛋白(16天)，但磷酸化的结节蛋白26直到感染细胞成熟(25天)才变得明显。磷酸化维持在稳定的水平，直到进入衰老。渗透胁迫(缺水和盐度)进一步增强了结节蛋白26的磷酸化。因此，结节蛋白26的磷酸化与成熟的固氮共生体的建立相吻合，受到渗透胁迫的调节，诱导钙信号通路，似乎是感染细胞对渗透挑战的适应性反应的一部分。
Soybean nodulin 26 is expressed and targeted to the symbiosome membrane of nitrogen-fixing nodules, where it forms an aquaporin channel with a modest water transport rate. In this study, we show that the phosphorylation of nodulin 26 on Ser-262, which is catalyzed by a symbiosome membrane-associated calcium-dependent protein kinase, stimulates its intrinsic water transport rate. Furthermore, using a phosphospecific antibody, we have elucidated the developmental appearance and regulation of nodulin 26 phosphorylation in vivo. Although nodulin 26 protein is detected first in differentiating infected cells (16 days), phosphorylated nodulin 26 does not become pronounced until infected cell maturation (25 days). Phosphorylation is sustained at steady state levels until entry into senescence. Nodulin 26 phosphorylation is enhanced further by osmotic stresses (water deprivation and salinity). Thus, the phosphorylation of nodulin 26 coincides with the establishment of mature nitrogen-fixing symbiosomes, is regulated by osmotic stresses that induce calcium-signaling pathways, and appears to be part of the adaptive responses of infected cells to osmotic challenge.