Department of Biochemistry, Cellular and Molecular Biology of Plants, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain.
Plant Physiol Biochem. 2012 Feb;51:109-15. doi: 10.1016/j.plaphy.2011.10.012. Epub 2011 Oct 28.
In general, wild tomato species are more salt tolerant than cultivated species, a trait that is related to enhanced Na(+) accumulation in aerial parts in the wild species, but the molecular basis for these differences is not known. Plant NHX proteins have been suggested to be important for salt tolerance by promoting accumulation of Na(+) or K(+) inside vacuoles. Therefore, differences in expression or activity of NHX proteins in tomato could be at the basis of the enhanced salt tolerance in wild tomato species. To test this hypothesis, we studied the expression level of four NHX genes in the salt sensitive cultivated species Solanum lycopersicum L. cv. Volgogradskij and the salt tolerant wild species Solanum pimpinelifolium L in response to salt stress. First, we determined that in the absence of salt stress, the RNA abundance of LeNHX2, 3 and 4 was comparable in both species, while more LeNHX1 RNA was detected in the tolerant species. LeNHX2 and LeNHX3 showed comparable expression levels and were present in all tissues, while LeNHX4 was expressed above all in stem and fruit tissues. Next, we confirmed that the wild species was more tolerant and accumulated more Na(+) in aerial parts of the plant. This correlated with the observation that salt stress induced especially the LeNHX3 and LeNHX4 isoforms in the tolerant species. These results support a role of NHX genes as determinants of salt tolerance in tomato, inducing enhanced Na(+) accumulation observed in the wild species when grown in the presence of NaCl.
一般来说，野生番茄物种比栽培物种更能耐受盐，这一特性与野生物种在地上部分积累更多 Na(+)有关，但这些差异的分子基础尚不清楚。植物 NHX 蛋白被认为通过促进 Na(+)或 K(+)在液泡内积累而对盐度耐受性很重要。因此，番茄中 NHX 蛋白的表达或活性差异可能是野生番茄物种增强耐盐性的基础。为了验证这一假说，我们研究了盐敏感栽培种 Solanum lycopersicum L. cv. Volgogradskij 和盐耐受野生种 Solanum pimpinelifolium L 中四个 NHX 基因在盐胁迫下的表达水平。首先，我们确定在没有盐胁迫的情况下，两种物种的 LeNHX2、3 和 4 的 RNA 丰度相当，而在耐受物种中检测到更多的 LeNHX1 RNA。LeNHX2 和 LeNHX3 表达水平相当，存在于所有组织中，而 LeNHX4 主要在茎和果实组织中表达。接下来，我们证实野生种更耐受，在植物地上部分积累更多的 Na(+)。这与观察到的在耐受物种中盐胁迫尤其诱导 LeNHX3 和 LeNHX4 同工型的结果一致。这些结果支持 NHX 基因作为番茄耐盐性决定因素的作用，在含有 NaCl 的情况下诱导野生种中观察到的增强的 Na(+)积累。
