Octanal was found to be able to reduce green mold incidence in citrus fruit by a defense response mechanism. However, the underlying mechanism remains largely unclear. Herein, the metabolomics, RNA-seq and biochemical analyses were integrated to explore the effect of octanal on disease resistance in harvested citrus fruit. Results showed that octanal fumigation at 40 μL L was effective in controlling citrus green mold. Metabolomics analysis showed that octanal mainly led to the accumulation of some plant hormones including methyl jasmonate, abscisic acid, indole-3-butyric acid, indoleacetic acid (IAA), salicylic acid, and gibberellic acid and many phenylpropanoid metabolites including cinnamyl alcohol, hesperidin, dihydrokaempferol, vanillin, quercetin-3-O-malonylglucoside, curcumin, naringin, chrysin, coniferin, calycosin-7-O-β-D-glucoside, -cinnamaldehyde, and 4′,5,7-trihydroxy-3,6-dimethoxyflavone. Particularly, IAA and hesperidin were dramatically accumulated in the peel, which might be the contributors to the resistance response. Additionally, transcriptome analysis showed that octanal greatly activated the biosynthesis and metabolism of aromatic amino acids. This was further verified by the accumulation of some metabolites (shikimic acid, tryptophan, tyrosine, phenylalanine, IAA, total phenolics, flavonoids and lignin), increase in some enzyme activities (phenylalanine ammonia-lyase, tyrosine ammonia-lyase, 4-coumarate CoA ligase, cinnamic acid 4-hydroxylase, polyphenol oxidase, and peroxidase), up-regulation of some genes (, , and ) expressions and molecular docking results. Thus, these results indicate that octanal is an efficient strategy for the control of postharvest green mold by triggering the defense response in citrus fruit.

中文翻译：

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辛醛通过芳香氨基酸的生物合成和代谢增强采后柑橘类水果的抗病性

研究发现辛醛能够通过防御反应机制减少柑橘类水果中绿霉菌的发生率。然而，其基本机制仍不清楚。在此，综合代谢组学、RNA-seq 和生化分析来探讨辛醛对收获的柑橘类水果抗病性的影响。结果表明，40 μL·L辛醛熏蒸可有效控制柑橘青霉病。代谢组学分析表明，辛醛主要导致茉莉酸甲酯、脱落酸、吲哚-3-丁酸、吲哚乙酸（IAA）、水杨酸、赤霉酸等植物激素以及肉桂醇、橙皮甙等多种苯丙素代谢物的积累。二氢山奈酚、香草醛、槲皮素-3-O-丙二酰葡萄糖苷、姜黄素、柚皮苷、白杨素、松柏苷、毛蕊异黄酮-7-O-β-D-葡萄糖苷、肉桂醛和4',5,7-三羟基-3,6-二甲氧基黄酮。特别是，IAA 和橙皮苷在果皮中大量积累，这可能是抵抗反应的贡献者。此外，转录组分析表明辛醛极大地激活了芳香族氨基酸的生物合成和代谢。一些代谢物（莽草酸、色氨酸、酪氨酸、苯丙氨酸、IAA、总酚、类黄酮和木质素）的积累、一些酶活性的增加（苯丙氨酸解氨酶、酪氨酸解氨酶、4-香豆酸辅酶A）进一步证实了这一点。连接酶、肉桂酸4-羟化酶、多酚氧化酶和过氧化物酶），一些基因（、、和）表达的上调和分子对接结果。因此，这些结果表明辛醛是通过触发柑橘类水果的防御反应来控制采后绿霉的有效策略。