A Comprehensive Biophysical Model of Ion and Water Transport in Plant Roots. II. Clarifying the Roles of SOS1 in the Salt-Stress Response in Arabidopsis
A Comprehensive Biophysical Model of Ion and Water Transport in Plant Roots. II. Clarifying the Roles of SOS1 in the Salt-Stress Response in Arabidopsis
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DOI：
10.3389/fpls.2019.01121
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发表时间：
2019-09-18
影响因子：
5.6
通讯作者：
Miklavcic, Stanley J.
中科院分区：
文献类型：
--
作者：
Foster, Kylie J.;Miklavcic, Stanley J.
SOS 1转运蛋白在植物耐盐性中起着重要作用。虽然已知SOS 1编码质膜Na+/H+逆向转运蛋白，但这些转运蛋白在整个根水平上促进耐盐性的转运机制尚不清楚。基因表达和通量测量提供了相互矛盾的证据的位置的SOS 1转运活性，使其难以确定其功能。SOS 1转运蛋白是否从根木质部蒸腾流中装载或卸载Na+还存在争议。为了解决这些领域的争论，我们应用数学模型来回答这个问题：SOS 1转运蛋白在盐胁迫拟南芥根的功能是什么？我们用我们的生物物理模型的离子和水在盐胁迫下的根运输模拟广泛的SOS 1转运蛋白的位置在一个模型拟南芥根，提供了一个详细的水平，目前不能通过实验来实现。我们将我们的模拟与现有的实验数据进行比较，以找到模型的合理参数，并确定SOS 1转运蛋白活性的可能位置。我们发现，SOS 1转运蛋白很可能在至少一个组织的外部成熟的根，在成熟的中柱，并在根尖的表皮。SOS 1在成熟的外根细胞中的转运活性对于维持根中低的细胞溶质Na+水平是必不可少的，并且也限制了Na+向芽的吸收。中柱中的SOS 1转运蛋白主动将Na+装载到木质部蒸腾流中，增强Na+和水向地上部的运输。SOS 1转运蛋白作用于根尖限制细胞溶质Na+浓度在根尖，但不能维持低的细胞溶质Na+水平在成熟的根。我们的研究结果表明，有针对性的，组织特异性过表达或敲除的SOS 1可能会导致更大的耐盐性比已经实现了组成型基因的变化。SOS 1表达的组织特异性变化可用于确定限制Na+吸收到芽中同时保持水分吸收之间的适当平衡，可能导致耐盐性的增强。
SOS1 transporters play an essential role in plant salt tolerance. Although SOS1 is known to encode a plasma membrane Na+/H+ antiporter, the transport mechanisms by which these transporters contribute to salt tolerance at the level of the whole root are unclear. Gene expression and flux measurements have provided conflicting evidence for the location of SOS1 transporter activity, making it difficult to determine their function. Whether SOS1 transporters load or unload Na+ from the root xylem transpiration stream is also disputed. To address these areas of contention, we applied a mathematical model to answer the question: what is the function of SOS1 transporters in salt-stressed Arabidopsis roots? We used our biophysical model of ion and water transport in a salt-stressed root to simulate a wide range of SOS1 transporter locations in a model Arabidopsis root, providing a level of detail that cannot currently be achieved by experimentation. We compared our simulations with available experimental data to find reasonable parameters for the model and to determine likely locations of SOS1 transporter activity. We found that SOS1 transporters are likely to be operating in at least one tissue of the outer mature root, in the mature stele, and in the epidermis of the root apex. SOS1 transporter activity in the mature outer root cells is essential to maintain low cytosolic Na+ levels in the root and also restricts the uptake of Na+ to the shoot. SOS1 transporters in the stele actively load Na+ into the xylem transpiration stream, enhancing the transport of Na+ and water to the shoot. SOS1 transporters acting in the apex restrict cytosolic Na+ concentrations in the apex but are unable to maintain low cytosolic Na+ levels in the mature root. Our findings suggest that targeted, tissue-specific overexpression or knockout of SOS1 may lead to greater salt tolerance than has been achieved with constitutive gene changes. Tissue-specific changes to the expression of SOS1 could be used to identify the appropriate balance between limiting Na+ uptake to the shoot while maintaining water uptake, potentially leading to enhancements in salt tolerance.