蜡质组成形态及其合成调控对小麦抗旱性的影响

Biosynthesis and regulation of cuticular wax and its effects on drought resistance of wheat

干旱对小麦产量有重要影响,蜡质与抗旱性关系密切,因此蜡质对小麦抗旱性和生产非常重要。蜡质具有防止水分的非气孔散失和气体交换、保护植物免受紫外线和强光辐射等生物和非生物胁迫的危害等重要生理功能。蜡质的合成过程非常复杂,大量的基因和转录因子参与了蜡质的合成和调控。蜡质的合成和运转受到转录、转录后和翻译水平的复杂调控,目前认为主要途径是转录水平的调节。干旱胁迫可以诱导植物蜡质含量的升高,组成和形态结构也随之改变,蜡质含量的升高和组成形态的改变反过来可以增强抗旱性。小麦蜡质可以显著提高光合作用与蒸腾作用的比值,最终提高籽粒和生物学产量。有关小麦蜡质的研究进展非常缓慢,小麦中具有独特的β-二酮蜡质合成途径,β-二酮的大量合成对小麦蜡质形态结构的影响、蜡质的合成和调控及其影响小麦抗旱性的生理机制都亟待深入研究。

Drought stress leads to dramatic annual yield losses in wheat, while cuticular wax plays important roles in drought resistance; therefore, wax is vital for improving wheat drought tolerance and productivity. The wax confers essential ecophysiological functions, including the prevention of non-stomatal water loss and gas exchange, protection of plant from ultraviolet light or high irradiation, and other abiotic and biotic stress. Cuticular wax biosynthesis is very complex, and a number of genes involved in wax biosynthesis have been characterized recently mostly from model plant Arabidopsis, as well as transcription factors（TFs） involved in the regulation of wax biosynthesis. Cuticular wax biosynthesis is regulated transcriptionally, post-transcriptionally, and post-translationally; however, transcriptional regulation is considered to be the major regulatory mechanism. It has been indicated that drought can induce increased wax deposition, together with varied composition and morphology. Meanwhile, increased amounts of cuticular wax have been associated with improved drought tolerance. Physiological studies in wheat found that wax significantly increased the photosynthesis to transpiration ratio in greenhouse experiments, and increased grain and biomass yield in irrigated and rainfed field experiments. The β-diketone pathway specific in wheat predominates in the reproductive stages. Despite its adaptive importance, the molecular mechanisms underlying variation in wheat wax especially for β-diketone and its association with drought tolerance remain to be investigated systematically.