Vera-Estrella Rosario, Barkla Bronwyn J, García-Ramírez Liliana, Pantoja Omar
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62250, Mexico.
Plant Physiol. 2005 Nov;139(3):1507-17. doi: 10.1104/pp.105.067850. Epub 2005 Oct 21.
Salinity is considered one of the major limiting factors for plant growth and agricultural productivity. We are using salt cress (Thellungiella halophila) to identify biochemical mechanisms that enable plants to grow in saline conditions. Under salt stress, the major site of Na+ accumulation occurred in old leaves, followed by young leaves and taproots, with the least accumulation occurring in lateral roots. Salt treatment increased both the H+ transport and hydrolytic activity of salt cress tonoplast (TP) and plasma membrane (PM) H(+)-ATPases from leaves and roots. TP Na(+)/H+ exchange was greatly stimulated by growth of the plants in NaCl, both in leaves and roots. Expression of the PM H(+)-ATPase isoform AHA3, the Na+ transporter HKT1, and the Na(+)/H+ exchanger SOS1 were examined in PMs isolated from control and salt-treated salt cress roots and leaves. An increased expression of SOS1, but no changes in levels of AHA3 and HKT1, was observed. NHX1 was only detected in PM fractions of roots, and a salt-induced increase in protein expression was observed. Analysis of the levels of expression of vacuolar H(+)-translocating ATPase subunits showed no major changes in protein expression of subunits VHA-A or VHA-B with salt treatment; however, VHA-E showed an increased expression in leaf tissue, but not in roots, when the plants were treated with NaCl. Salt cress plants were able to distribute and store Na+ by a very strict control of ion movement across both the TP and PM.
盐度被认为是植物生长和农业生产力的主要限制因素之一。我们正在利用盐芥（Thellungiella halophila）来确定使植物能够在盐渍条件下生长的生化机制。在盐胁迫下，Na+积累的主要部位发生在老叶，其次是幼叶和主根，侧根中积累最少。盐处理增加了盐芥叶片和根的液泡膜（TP）和质膜（PM）H(+)-ATP酶的H+转运和水解活性。植物在NaCl中生长时，叶片和根中的TP Na(+)/H+交换都受到极大刺激。在从对照和盐处理的盐芥根和叶中分离的质膜中检测了PM H(+)-ATP酶亚型AHA3、Na+转运体HKT1和Na(+)/H+交换体SOS1的表达。观察到SOS1表达增加，但AHA3和HKT1水平没有变化。NHX1仅在根的质膜部分检测到，并且观察到盐诱导的蛋白质表达增加。对液泡H(+)-转运ATP酶亚基表达水平的分析表明，盐处理后VHA-A或VHA-B亚基的蛋白质表达没有重大变化；然而，当植物用NaCl处理时，VHA-E在叶组织中表达增加，但在根中没有增加。盐芥植物能够通过非常严格地控制离子跨TP和PM的移动来分布和储存Na+。
