Shabala Sergey, Chen Xi, Yun Ping, Zhou Meixue
School of Biological Science, University of Western Australia, Crawley, WA6009, Australia.
International Research Centre for Environmental Membrane Biology, Foshan University, Foshan 528000, China.
J Exp Bot. 2025 Apr 9. doi: 10.1093/jxb/eraf152.
Wheat is the major staple food in the human diet but its production under current climate scenarios is problematic, giving the predicted extent of land salinization and the fact that wheat is highly sensitive to soil salinity. This work aims to critically assess previous breeding efforts and pros- and cons- of targeting SOS1 and HKT1 genes to improve salinity stress tolerance in wheat. We argue that overexpressing SOS1 genes encoding Na+/H+ exchangers for Na+ removal from root to the rhizosphere may come with a caveat of increased loading of Na+ into the xylem and its delivery to the shoot, as well as numerous pleiotropic effects. Similarly, targeting HKT1 transporters for removing Na+ from the shoot comes with significant yield penalties due to the high carbon cost for osmotic adjustment; this strategy is also limited by the relatively small capacity of the root to store excessive Na+ without experiencing toxicity symptoms. We suggest that targeting tissue tolerance traits such as K+ retention in mesophyll and vacuolar Na+ sequestration in the shoot will be able to deliver better outcomes. We also call for a better understanding of the structure-function relationships of various isoforms for key genes involved in maintenance of Na+ and K+ homeostasis and a need for more in-depth physiological studies of wheat species with DD genome; a key contributor to tissue tolerance traits. Our arguments are supported by the bioinformatic analysis of the number of orthologs for some key gene between hexaploidy (AABBDD) and tetraploid (AABB) wheats and their structural differences.
小麦是人类饮食中的主要主食，但在当前气候情景下其生产存在问题，考虑到预计的土地盐碱化程度以及小麦对土壤盐分高度敏感这一事实。这项工作旨在严格评估以往的育种努力，以及针对SOS1和HKT1基因来提高小麦耐盐胁迫能力的利弊。我们认为，过表达编码Na⁺/H⁺ 交换体的SOS1基因以将Na⁺ 从根部转运到根际，可能会带来将更多Na⁺ 加载到木质部并输送到地上部的风险，以及众多的多效性影响。同样，针对HKT1转运蛋白以从地上部去除Na⁺ 的策略，由于渗透调节的高碳成本会导致显著的产量损失；该策略还受到根部在不出现毒性症状的情况下储存过量Na⁺ 的能力相对较小的限制。我们建议，针对组织耐受性状，如叶肉中K⁺ 的保留和地上部液泡中Na⁺ 的隔离，将能够带来更好的结果。我们还呼吁更好地理解参与维持Na⁺ 和K⁺ 稳态的关键基因的各种异构体的结构 - 功能关系，以及需要对具有DD基因组的小麦物种进行更深入的生理研究；DD基因组是组织耐受性状的关键贡献者。我们的观点得到了对六倍体（AABBDD）和四倍体（AABB）小麦之间一些关键基因的直系同源物数量及其结构差异的生物信息学分析的支持。
