Department of Grassland Science, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China.
Department of Grassland Science, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, China; Institute of Qinghai-Tibetan Plateau, Southwest University for Nationalities, Chengdu 610041, China.
Plant Physiol Biochem. 2018 Aug;129:251-263. doi: 10.1016/j.plaphy.2018.06.009. Epub 2018 Jun 9.
Endogenous hormones and polyamines (PAs) could interact to regulate growth and tolerance to water stress in white clover. The objective of this study was to investigate whether the alteration of endogenous indole-3-acetic acid (IAA) level affected other hormones level and PAs metabolism contributing to the regulation of tolerance to water stress in white clover. Plants were pretreated with IAA or L-2-aminooxy-3-phenylpropionic acid (L-AOPP, the inhibitor of IAA biosynthesis) for 3 days and then subjected to water-sufficient condition and water stress induced by 15% polyethylene glycol 6000 for 8 days in growth chambers. Exogenous application of IAA significantly increased endogenous IAA, gibberellin (GA), abscisic acid (ABA), and polyamine (PAs) levels, but had no effect on cytokinin content under water stress. The increase in endogenous IAA level enhanced PAs anabolism via the improvement of enzyme activities and transcript level of genes including arginine decarboxylase, ornithine decarboxylase, and S-adenosylmethionine decarboxylase. Exogenous application of IAA also affected PAs catabolism, as manifested by an increase in diamine oxidase and a decrease in polyamine oxidase activities and genes expression. More importantly, the IAA deficiency in white clover decreased endogenous hormone levels (GA, ABA, and PAs) and PAs anabolism along with decline in antioxidant defense and osmotic adjustment (OA). On the contrary, exogenous IAA effectively alleviated stress-induced oxidative damage, growth inhibition, water deficit, and leaf senescence through the maintenance of higher chlorophyll content, OA, and antioxidant defense as well as lower transcript levels of senescence marker genes SAG101 and SAG102 in leaves under water stress. These results indicate that IAA-induced the crosstalk between endogenous hormones and PAs could be involved in the improvement of antioxidant defense and OA conferring tolerance to water stress in white clover.
内源性激素和多胺（PAs）可以相互作用调节白三叶草的生长和对水分胁迫的耐受性。本研究的目的是探讨内源吲哚-3-乙酸（IAA）水平的改变是否会影响其他激素水平和 PAs 代谢，从而调节白三叶草对水分胁迫的耐受性。植物用 IAA 或 L-2-氨基氧-3-苯丙酸（L-AOPP，IAA 生物合成抑制剂）预处理 3 天，然后在生长室中进行水分充足和 15%聚乙二醇 6000 诱导的水分胁迫 8 天。外源施用 IAA 显著增加了内源 IAA、赤霉素（GA）、脱落酸（ABA）和多胺（PAs）水平，但在水分胁迫下对细胞分裂素含量没有影响。内源 IAA 水平的提高通过提高包括精氨酸脱羧酶、鸟氨酸脱羧酶和 S-腺苷甲硫氨酸脱羧酶在内的基因的酶活性和转录水平，增强了 PAs 的合成代谢。外源施用 IAA 还影响 PAs 的分解代谢，表现为二胺氧化酶活性增加和多胺氧化酶活性及基因表达降低。更重要的是，白三叶草中 IAA 的缺乏降低了内源激素水平（GA、ABA 和 PAs）和 PAs 的合成代谢，同时降低了抗氧化防御和渗透调节（OA）。相反，外源 IAA 通过维持更高的叶绿素含量、OA 和抗氧化防御，以及降低叶片衰老标记基因 SAG101 和 SAG102 的转录水平，有效缓解了水分胁迫引起的氧化损伤、生长抑制、水分亏缺和叶片衰老。这些结果表明，IAA 诱导的内源激素和 PAs 之间的串扰可能参与了提高抗氧化防御和 OA，从而赋予白三叶草对水分胁迫的耐受性。
