Nahar Lutfun, Aycan Murat, Hanamata Shigeru, Baslam Marouane, Mitsui Toshiaki
Department of Life and Food Sciences, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Department of Agricultural Botany, Sher-e-Bangla Agricultural University, Dhaka 1207, Bangladesh.
Plants (Basel). 2022 Feb 12;11(4):501. doi: 10.3390/plants11040501.
Here, for the first time, we aimed to identify in rice the key mechanisms and processes underlying tolerance to high-temperature (HT) or salt stress (SS) alone, the co-occurrence of both stresses, and recovery using physiological and biochemical measurements and gene expression analysis. We also investigated whether recovery from the two stressors depended on the relative intensities/relief of each stressor. Wild type ('Yukinkomai') rice plants were found to be more susceptible to salinity or heat applied individually. SS leads to a depletion of cellular water content, higher accumulation of Na, and alterations in photosynthetic pigments. The stress-tolerant cultivar 'YNU31-2-4' (YNU) displayed a lower Na/K ratio, higher water content in cells and improved photosynthetic traits, antioxidant system, and expression of defence genes. Strikingly, the SS + HT combination provided a significant level of protection to rice plants from the effects of SS alone. The expression pattern of a selected set of genes showed a specific response and dedicated pathways in plants subjected to each of the different stresses, while other genes were explicitly activated when the stresses were combined. Aquaporin genes were activated by SS, while stress-related (, , , and ions transporters) genes were shaped by HT. Hierarchical clustering and principal component analyses showed that several traits exhibited a gradually aggravating effect as plants were exposed to the combined stresses and identified heat as a mitigating factor, clearly separating heat + salt-stressed from salt-non-heat-stressed plants. Furthermore, seedling recovery was far more dependent on the relative intensities of stressors and cultivars, demonstrating the influence of one stressor over another upon stress-release. Taken together, our data show the uniqueness and complexity of the physiological and molecular network modules used by rice plants to respond to single and combined stresses and recovery.
在此，我们首次旨在通过生理生化测量和基因表达分析，确定水稻中单独耐受高温（HT）或盐胁迫（SS）、两种胁迫同时发生以及恢复过程的关键机制和进程。我们还研究了从两种胁迫源恢复是否取决于每种胁迫源的相对强度/缓解情况。发现野生型（‘雪印小町’）水稻植株对单独施加的盐分或热量更敏感。盐胁迫导致细胞含水量减少、钠积累增加以及光合色素改变。耐胁迫品种‘YNU31 - 2 - 4’（YNU）表现出较低的钠/钾比、较高的细胞含水量以及改善的光合特性、抗氧化系统和防御基因表达。令人惊讶的是，盐胁迫 + 高温组合为水稻植株提供了显著水平的保护，使其免受单独盐胁迫的影响。一组选定基因的表达模式显示，在遭受每种不同胁迫的植物中存在特定反应和专门途径，而当胁迫组合时，其他基因被明确激活。水通道蛋白基因被盐胁迫激活，而与胁迫相关的（、、和离子转运蛋白）基因受高温影响。层次聚类和主成分分析表明，随着植物暴露于组合胁迫下，几个性状表现出逐渐加重的影响，并确定高温为缓解因素，将热 + 盐胁迫植物与非热盐胁迫植物明显区分开来。此外，幼苗恢复在更大程度上取决于胁迫源的相对强度和品种，表明一种胁迫源对另一种胁迫源在胁迫解除时的影响。综上所述，我们的数据显示了水稻植株用于应对单一和组合胁迫及恢复的生理和分子网络模块的独特性和复杂性。
