CSIRO Agriculture and Food, GPO Box 1700, Canberra, ACT 2601, Australia.
CSIRO Centre for Environment and Life Sciences, 147 Underwood Avenue, Floreat, WA 6014, Australia.
Genes (Basel). 2021 Oct 29;12(11):1742. doi: 10.3390/genes12111742.
Drought stress requires plants to adjust their water balance to maintain tissue water levels. Isohydric plants ('water-savers') typically achieve this through stomatal closure, while anisohydric plants ('water-wasters') use osmotic adjustment and maintain stomatal conductance. Isohydry or anisohydry allows plant species to adapt to different environments. In this paper we show that both mechanisms occur in bread wheat ( L.). Wheat lines with reproductive drought-tolerance delay stomatal closure and are temporarily anisohydric, before closing stomata and become isohydric at higher threshold levels of drought stress. Drought-sensitive wheat is isohydric from the start of the drought treatment. The capacity of the drought-tolerant line to maintain stomatal conductance correlates with repression of ABA synthesis in spikes and flag leaves. Gene expression profiling revealed major differences in the drought response in spikes and flag leaves of both wheat lines. While the isohydric drought-sensitive line enters a passive growth mode (arrest of photosynthesis, protein translation), the tolerant line mounts a stronger stress defence response (ROS protection, LEA proteins, cuticle synthesis). The drought response of the tolerant line is characterised by a strong response in the spike, displaying enrichment of genes involved in auxin, cytokinin and ethylene metabolism/signalling. While isohydry may offer advantages for longer term drought stress, anisohydry may be more beneficial when drought stress occurs during the critical stages of wheat spike development, ultimately improving grain yield.
干旱胁迫要求植物调整其水平衡以维持组织内的水分含量。等水植物（“节水型”植物）通常通过关闭气孔来实现这一点，而异水植物（“耗水型”植物）则利用渗透调节并维持气孔导度。等水特性或异水特性使植物物种能够适应不同的环境。在本文中，我们表明这两种机制都存在于小麦（ L.）中。具有生殖耐旱性的小麦品系延迟气孔关闭，并在更高的干旱胁迫阈值水平下暂时异水，然后关闭气孔并成为等水。从干旱处理开始，敏感小麦就是等水的。耐旱品系维持气孔导度的能力与穗和旗叶中 ABA 合成的抑制有关。基因表达谱分析揭示了两种小麦品系穗和旗叶在干旱响应方面的主要差异。等水敏感的品系进入被动生长模式（光合作用、蛋白质翻译停止），而耐旱的品系则会产生更强的应激防御反应（ROS 保护、LEA 蛋白、角质层合成）。耐旱品系的干旱反应以穗部的强烈反应为特征，表现为参与生长素、细胞分裂素和乙烯代谢/信号转导的基因富集。虽然等水特性可能对长期干旱胁迫有优势，但在小麦穗发育的关键阶段发生干旱胁迫时，异水特性可能更有利，最终提高籽粒产量。
