National Institute of Plant Genome Research, New Delhi, India.
Physiol Plant. 2021 Apr;171(4):620-637. doi: 10.1111/ppl.13210. Epub 2020 Sep 29.
Abiotic stresses, including drought and salinity, negatively affect plant development and physiology at molecular and metabolic levels. Sucrose transport, mediating distribution of photosynthates in plant, is a key physiological process impacted by drought and salinity stresses, as sucrose is a prime energy and signaling molecule as well as an osmolyte. Therefore, understanding the effects of abiotic stresses on sucrose transport and transporters, and underlying genetic and molecular mechanisms, is imperative to maintain sugar homeostasis in plants under stress. Here, we investigated the effects of drought and salinity stresses on sucrose transport and distribution, and on expression levels of genes encoding Sugars Will Eventually be Exported Transporters (SWEETs), along with a potential transcription factor regulating SWEET expression in rice. We observed that drought and salinity stresses increased the sucrose content in leaf and root tissues and in phloem sap of rice indica varieties. Expression analyses of SWEET genes and histochemical analysis of β-glucuronidase-reporter transgenic plants suggested that OsSWEET13 and OsSWEET15 are major SWEET transporters regulating the sucrose transport and levels in response to the abiotic stresses. Transactivation analyses showed that an abscisic acid (ABA)-responsive transcription factor OsbZIP72 directly binds to the promoters of OsSWEET13 and OsSWEET15 and activates their expression. Taken together, the results showed that the higher expressions of OsSWEET13 and OsSWEET15 genes, induced by binding of an ABA-responsive transcription factor OsbZIP72 to the promoters, potentially modulate sucrose transport and distribution in response to the abiotic stresses. The mechanism could possibly be targeted for maintaining sugar homeostasis in rice under drought and salinity stresses.
非生物胁迫，包括干旱和盐胁迫，会在分子和代谢水平上对植物的发育和生理产生负面影响。蔗糖转运作为一种关键的生理过程，介导了植物中光合产物的分配，它受到干旱和盐胁迫的影响，因为蔗糖是一种主要的能量和信号分子，也是一种渗透调节剂。因此，了解非生物胁迫对蔗糖转运和转运蛋白的影响，以及潜在的遗传和分子机制，对于维持植物在胁迫下的糖稳态至关重要。在这里，我们研究了干旱和盐胁迫对蔗糖转运和分布的影响，以及对编码蔗糖将最终被输出的转运蛋白（SWEETs）基因表达水平的影响，同时还研究了一个潜在的转录因子对水稻中 SWEET 表达的调控。我们观察到，干旱和盐胁迫增加了水稻籼稻品种叶片和根组织以及韧皮部汁液中的蔗糖含量。SWEET 基因的表达分析和β-葡萄糖醛酸酶报告转基因植物的组织化学分析表明，OsSWEET13 和 OsSWEET15 是主要的 SWEET 转运蛋白，它们调节蔗糖的转运和水平，以响应非生物胁迫。转激活分析表明，一种脱落酸（ABA）响应转录因子 OsbZIP72 直接结合到 OsSWEET13 和 OsSWEET15 的启动子上，并激活它们的表达。综上所述，这些结果表明，ABA 响应转录因子 OsbZIP72 与启动子结合，诱导 OsSWEET13 和 OsSWEET15 基因的高表达，可能调节蔗糖的转运和分布，以响应非生物胁迫。该机制可能可以作为在干旱和盐胁迫下维持水稻糖稳态的目标。
