Main conclusion In this study, we show that ectopic expression of either HtNHX1 or HtNHX2, from Helianthus tuberosus plant (located at vacuolar and endosome membranes, respectively), in rice plants could enhance its tolerance to aluminum (Al 3+ ) stress and soil acidity. Abstract Plant sodium (potassium)/proton (Na + (K + )/H + antiporters of the NHX family have been extensively characterized as they are related to the enhancement of salt tolerance. However, no previous study has reported NHX transporter functions in plant tolerance to Al 3+ toxicity. In this study, we demonstrate their role as a component of the Al 3+ stress tolerance mechanism. We show that the ectopic expression of either HtNHX1 or HtNHX2 , from Helianthus tuberosus plant, in rice (located at vacuole and endosome, respectively) could also enhance rice tolerance to Al 3+ stress and soil acidity. Expression of either HtNHX1 or HtNHX2 reduced the inhibitory effect of Al 3+ on the rice root elongation rate; both genes were reported to be equally effective in improvement of stress conditions. Expression of HtNHX1 enhanced Al 3+ -trigged-secretion of citrate acids, rhizosphere acidification, and also reduced K + efflux from root tissues. In contrast, expression of HtNHX2 prevented Al 3+ -trigged-decrease of H + influx into root tissues . Al 3+ -induced damage of the cell wall extensibility at the root tips was impaired by either HtNHX1 or HtNHX2 . Co-expression of HtNHX1 and HtNHX2 further improved rice growth, particularly under the Al 3+ stress conditions. The results demonstrate that HtNHX1 and HtNHX2 improved rice tolerance to Al 3+ via different mechanisms by altering the K + and H + fluxes and the cell wall structure.

中文翻译：

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NHX型转运蛋白在提高水稻对铝胁迫和土壤酸度耐受性中的作用

主要结论 在本研究中，我们表明，HtNHX1 或 HtNHX2（分别位于液泡膜和内体膜）在水稻植物中的异位表达可以增强其对铝 (Al 3+ ) 胁迫和土壤酸度的耐受性. 摘要 植物钠（钾）/质子（Na + (K + )/H + NHX 家族的逆向转运蛋白与提高耐盐性有关，已被广泛表征。然而，以往的研究没有报道植物中的 NHX 转运蛋白功能。对 Al 3+ 毒性的耐受性。在这项研究中，我们证明了它们作为 Al 3+ 胁迫耐受机制的一个组成部分的作用。我们表明，来自向日葵植物的 HtNHX1 或 HtNHX2 在水稻（位于液泡处）的异位表达和内体，分别）还可以增强水稻对Al 3+ 胁迫和土壤酸度的耐受性。HtNHX1或HtNHX2的表达降低了Al 3+ 对水稻根系伸长率的抑制作用；据报道，这两种基因在改善压力条件方面同样有效。HtNHX1 的表达增强了柠檬酸的Al 3+ 触发分泌、根际酸化，并且还减少了根组织的K + 流出。相反，HtNHX2 的表达阻止了Al 3+ 触发的H + 流入根组织的减少。HtNHX1 或HtNHX2 损害了Al 3+ 诱导的根尖细胞壁延伸性损伤。HtNHX1 和HtNHX2 的共表达进一步改善了水稻的生长，特别是在Al 3+ 胁迫条件下。