Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543.
Plant Cell Environ. 2013 Aug;36(8):1410-22. doi: 10.1111/pce.12068. Epub 2013 Feb 21.
The specialized salt glands on the epidermis of halophytic plants secrete excess salts from tissues by a mechanism that is poorly understood. We examined the salt glands as putative salt and water bi-regulatory units that can respond swiftly to altering environmental cues. The tropical mangrove tree species (Avicennia officinalis) is able to grow under fluctuating salinities (0.7-50.0 dS m(-1)) at intertidal zones, and its salt glands offer an excellent platform to investigate their dynamic responses under rapidly changing salinities. Utilizing a novel epidermal peel system, secretion profiles of hundreds of individual salt glands examined revealed that these glands could secrete when exposed to varying salinities. Notably, rhythmic fluctuations observed in secretion rates were reversibly inhibited by water channel (aquaporin) blocker, and two aquaporin genes (PIP and TIP) preferentially expressed in the salt gland cells were rapidly induced in response to increasing salt concentration. We propose that aquaporins are involved and contribute to the re-absorption of water during salt removal in Avicennia officinalis salt glands. This constitutes an adaptive feature that contributes to salt balance of trees growing in saline environments where freshwater availability is limited.
盐生植物表皮上的特化盐腺通过一种尚未完全理解的机制将组织内的多余盐分分泌出来。我们研究了盐腺，认为它们是盐和水的双调控单位，能够对不断变化的环境信号迅速做出反应。热带红树林物种（桐花树）能够在潮间带波动的盐度（0.7-50.0 dS m(-1))下生长，其盐腺为研究它们在快速变化的盐度下的动态反应提供了一个极好的平台。利用一种新颖的表皮剥离系统，对数百个单个盐腺的分泌谱进行了检测，结果表明这些盐腺在暴露于不同盐度时可以分泌。值得注意的是，水通道（水孔蛋白）阻断剂可逆地抑制了分泌速率的波动，并且在盐浓度增加时，两种在盐腺细胞中优先表达的水孔蛋白基因（PIP 和 TIP）迅速被诱导。我们提出，水孔蛋白参与并有助于桐花树盐腺中盐分去除过程中的水分再吸收。这是一种适应性特征，有助于在淡水供应有限的盐环境中生长的树木维持盐平衡。
