Department of Resources and Environmental Science, Shihezi University, Shihezi, Xinjiang, People's Republic of China.
PLoS One. 2019 Dec 23;14(12):e0226776. doi: 10.1371/journal.pone.0226776. eCollection 2019.
Soil salinity is a major abiotic stress factor that limits cotton production worldwide. To improve salt tolerance in cotton, an in-depth understanding of ionic balance is needed. In this study, a pot experiment using three levels of soil salinity (0%, 0.2%, and 0.4%, represented as CK, SL, and SH, respectively) and two cotton genotypes (salt-tolerant genotype: L24; salt-sensitive genotype: X45) was employed to investigate how sodium chloride (NaCl) stress effects cotton growth, ion distribution, and transport, as well as to explore the related mechanism. The results showed that SL treatment mainly inhibited shoot growth, while SH treatment caused more extensive impairment to roots and shoots. The growth inhibition ratio of NaCl stress on X45 was more marked than that of L24. Under NaCl stress, the Na concentration in the roots, stems and leaves significantly increased, whereas the K, Cu, B, and Mo concentration in roots, as well as Mg and S concentrations in the leaves, significantly decreased. Under salt stress conditions, salt-tolerant cotton plants can store Na in the leaves, and as a result, a larger amount of minerals (e.g., Cu, Mo, Si, P, and B) tend to transport to the leaves. By contrast, salt-sensitive varieties tend to accumulate certain minerals (e.g., Ca, P, Mg, S, Mn, Fe, Cu, B, Mo, and Si) in the roots. Most genes related to ion transport and homeostasis were upregulated in L24, but not in X45. The expression level of GhSOS1 in X45 was higher than L24, but GhNHX1 in L24 was higher than X45. Our findings suggest that the two varieties response to salt stress differently; for X45 (salt-sensitive), the response is predominantly governed by Na+ efflux, whereas for L24 (salt-tolerant), vacuolar sequestration of Na+ is the major mechanism. The expression changes of the genes encoding the ion transporters may partially explain the genotypic difference in leaf ion accumulation under salt stress conditions.
土壤盐度是限制全球棉花生产的主要非生物胁迫因素。为了提高棉花的耐盐性，需要深入了解离子平衡。本研究采用盆栽试验，设置 3 个土壤盐度水平（0%、0.2%和 0.4%，分别表示为 CK、SL 和 SH）和 2 个棉花基因型（耐盐基因型：L24；盐敏感基因型：X45），研究氯化钠（NaCl）胁迫对棉花生长、离子分布和运输的影响，探讨相关机制。结果表明，SL 处理主要抑制地上部生长，而 SH 处理对根和地上部的损伤更为广泛。NaCl 胁迫对 X45 的生长抑制率大于 L24。在 NaCl 胁迫下，根、茎和叶中的 Na 浓度显著增加，而根中的 K、Cu、B 和 Mo 浓度以及叶中的 Mg 和 S 浓度显著降低。在盐胁迫条件下，耐盐棉花可以将 Na 储存在叶片中，因此更多的矿物质（如 Cu、Mo、Si、P 和 B）倾向于运输到叶片中。相比之下，盐敏感品种往往会在根部积累某些矿物质（如 Ca、P、Mg、S、Mn、Fe、Cu、B、Mo 和 Si）。与离子转运和稳态相关的大多数基因在 L24 中上调，但在 X45 中没有上调。X45 中 GhSOS1 的表达水平高于 L24，但 L24 中 GhNHX1 的表达水平高于 X45。我们的研究结果表明，两个品种对盐胁迫的反应不同；对于 X45（盐敏感），反应主要受 Na+外排控制，而对于 L24（耐盐），Na+的液泡隔离是主要机制。离子转运体基因的表达变化部分解释了叶片离子在盐胁迫条件下积累的基因型差异。
