Laboratorio de Biología Molecular Vegetal, Facultad de Ciencias, Universidad de la República, Iguá 4225, CP 11400 Montevideo, Uruguay.
Plant Sci. 2012 Jul;190:89-102. doi: 10.1016/j.plantsci.2012.03.009. Epub 2012 Apr 17.
The moss Physcomitrella patens can withstand extreme environmental conditions including drought and salt stress. Tolerance to dehydration in mosses is thought to rely on efficient limitation of stress-induced cell damage and repair of cell injury upon stress relief. Dehydrin proteins (DHNs) are part of a conserved cell protecting mechanism in plants although their role in stress tolerance is not well understood. Four DHNs and two DHN-like proteins were identified in the predicted proteome of P. patens. Expression of PpDHNA and PpDHNB was induced by salt and osmotic stress and controlled by abscisic acid. Subcellular localization of the encoded proteins suggested that these dehydrins are localized in cytosol and accumulate near membranes during stress. Comparative analysis of dhnA and dhnB targeted knockout mutants of P. patens revealed that both genes play a role in cellular protection during salt and osmotic stress, although PpDHNA has a higher contribution to stress tolerance. Overexpression of PpDHNA and PpDHNB genes in transgenic Arabidopsis improved rosette and root growth in stress conditions, although PpDHNA was more efficient in this role. These results suggest that specific DHNs contribute considerably to the high stress tolerance of mosses and offer novel tools for genetic engineering stress tolerance of higher plants.
藓类植物拟南芥能够耐受包括干旱和盐胁迫在内的极端环境条件。人们认为，藓类植物对脱水的耐受性依赖于对胁迫诱导的细胞损伤的有效限制，以及在胁迫缓解时对细胞损伤的修复。脱水素蛋白（DHN）是植物中一种保守的细胞保护机制的一部分，尽管其在耐受胁迫方面的作用尚未得到很好的理解。在拟南芥的预测蛋白质组中鉴定出了 4 种 DHN 和 2 种 DHN 样蛋白。PpDHNA 和 PpDHNB 的表达受盐和渗透胁迫诱导，并受脱落酸调控。编码蛋白的亚细胞定位表明，这些脱水素定位于细胞质中，并在胁迫期间在膜附近积累。对拟南芥的 dhnA 和 dhnB 靶向敲除突变体进行比较分析表明，这两个基因在盐和渗透胁迫下的细胞保护中都发挥作用，尽管 PpDHNA 对胁迫耐受性的贡献更高。在转基因拟南芥中过表达 PpDHNA 和 PpDHNB 基因可改善胁迫条件下的莲座叶和根的生长，尽管 PpDHNA 在这方面的效率更高。这些结果表明，特定的 DHN 对藓类植物的高胁迫耐受性有很大贡献，并为高等植物的遗传工程胁迫耐受性提供了新的工具。
