Kelly Gilor, Sade Nir, Doron-Faigenboim Adi, Lerner Stephen, Shatil-Cohen Arava, Yeselson Yelena, Egbaria Aiman, Kottapalli Jayaram, Schaffer Arthur A, Moshelion Menachem, Granot David
Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, 7505101, Israel.
The Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 76100, Israel.
Plant J. 2017 Jul;91(2):325-339. doi: 10.1111/tpj.13568. Epub 2017 May 15.
Sugars affect central aspects of plant physiology, including photosynthesis, stomatal behavior and the loss of water through the stomata. Yet, the potential effects of sugars on plant aquaporins (AQPs) and water conductance have not been examined. We used database and transcriptional analyses, as well as cellular and whole-plant functional techniques to examine the link between sugar-related genes and AQPs. Database analyses revealed a high level of correlation between the expression of AQPs and that of sugar-related genes, including the Arabidopsis hexokinases 1 (AtHXK1). Increased expression of AtHXK1, as well as the addition of its primary substrate, glucose (Glc), repressed the expression of 10 AQPs from the plasma membrane-intrinsic proteins (PIP) subfamily (PIP-AQPs) and induced the expression of two stress-related PIP-AQPs. The osmotic water permeability of mesophyll protoplasts of AtHXK1-expressing plants and the leaf hydraulic conductance of those plants were significantly reduced, in line with the decreased expression of PIP-AQPs. Conversely, hxk1 mutants demonstrated a higher level of hydraulic conductance, with increased water potential in their leaves. In addition, the presence of Glc reduced leaf water potential, as compared with an osmotic control, indicating that Glc reduces the movement of water from the xylem into the mesophyll. The production of sugars entails a significant loss of water and these results suggest that sugars and AtHXK1 affect the expression of AQP genes and reduce leaf water conductance, to coordinate sugar levels with the loss of water through transpiration.
糖类影响植物生理学的核心方面，包括光合作用、气孔行为以及通过气孔的水分流失。然而，糖类对植物水通道蛋白（AQP）和水分传导的潜在影响尚未得到研究。我们运用数据库和转录分析以及细胞和全株功能技术来研究糖相关基因与水通道蛋白之间的联系。数据库分析揭示了水通道蛋白的表达与糖相关基因（包括拟南芥己糖激酶1，AtHXK1）的表达之间存在高度相关性。AtHXK1表达的增加以及其主要底物葡萄糖（Glc）的添加，抑制了质膜内在蛋白（PIP）亚家族中10种水通道蛋白（PIP-AQPs）的表达，并诱导了两种与胁迫相关的PIP-AQPs的表达。与PIP-AQPs表达的降低一致，表达AtHXK1的植物叶肉原生质体的渗透水通透性和这些植物的叶片水力传导率显著降低。相反，hxk1突变体表现出更高的水力传导率，其叶片中的水势增加。此外，与渗透对照相比，Glc的存在降低了叶片水势，表明Glc减少了水分从木质部进入叶肉的移动。糖类的产生伴随着大量的水分流失，这些结果表明糖类和AtHXK1影响水通道蛋白基因的表达并降低叶片水分传导率，以通过蒸腾作用使糖水平与水分流失相协调。
