Main conclusion This report proves a cross talk between H 2 S and IAA in cold stress response, which has presented strong evidence that IAA acts as a downstream signal mediating the H 2 S-induced stress tolerance in cucumber seedlings. Abstract We evaluated changes in endogenous hydrogen sulfide (H 2 S) and indole-3-acetic acid (IAA) emission systems, and the interactive effect of exogenous H 2 S and IAA on chilling tolerance in cucumber seedlings. The results showed that chilling stress increased the activity and relative mRNA expression of l -/ d -cysteine desulfhydrase ( l -/ d -CD), which in turn induced the accumulation of endogenous H 2 S. Similarly, the endogenous IAA system was triggered by chilling stress. We found that 1.0 mM sodium hydrosulfide (NaHS, an H 2 S donor) significantly enhanced the activity of flavin monooxygenase (FMO) and relative expression of FMO-like proteins ( YUCCA2 ), which in turn elevated endogenous IAA levels in cucumber seedlings. However, IAA had little effects on activities of l -/ d -CD and endogenous H 2 S levels. H 2 S-induced IAA production accompanied by increase in chilling tolerance, as shown by the decrease in stress-induced electrolyte leakage (EL) and reactive oxygen species (ROS) accumulation, and increase in gene expressions and enzyme activities of photosynthesis. 1-naphthylphthalamic acid (NPA, an IAA polar transport inhibitor) declined H 2 S-induced chilling tolerance and defense genes’ expression. However, scavenging of H 2 S had a little effect on IAA-induced chilling tolerance. These results suggest that IAA acting as a downstream signaling molecule is involved in the H 2 S-induced chilling tolerance in cucumber seedlings.

中文翻译：

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生长素作为下游信号分子参与硫化氢诱导的黄瓜耐寒性

主要结 摘要 我们评估了内源硫化氢（H 2 S）和吲哚-3-乙酸（IAA）排放系统的变化，以及外源H 2 S和IAA对黄瓜幼苗耐寒性的交互作用。结果表明，低温胁迫增加了l-/d-半胱氨酸脱硫酶(l-/d-CD)的活性和mRNA相对表达量，进而诱导了内源性H 2 S的积累。同样，内源性IAA系统被触发。通过寒冷的压力。我们发现 1.0 mM 硫氢化钠 (NaHS, H 2 S 供体）显着增强了黄素单加氧酶 (FMO) 的活性和 FMO 样蛋白 (YUCCA2) 的相对表达，进而提高了黄瓜幼苗中内源性 IAA 水平。而IAA对l -/ d -CD活性和内源性H 2 S水平影响不大。H 2 S 诱导的 IAA 产生伴随着耐寒性的增加，表现为应激诱导的电解质泄漏 (EL) 和活性氧 (ROS) 积累的减少，以及光合作用的基因表达和酶活性的增加。1-萘基邻苯二甲酸（NPA，一种 IAA 极性转运抑制剂）降低了 H 2 S 诱导的耐寒性和防御基因的表达。然而，H 2 S 的清除对 IAA 诱导的耐寒性影响不大。