Key Laboratory of Protected Horticulture of Education Ministry and Liaoning Province, College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.
J Zhejiang Univ Sci B. 2018;19(8):596-609. doi: 10.1631/jzus.B1700388.
In plants, lipoxygenases (LOXs) play a crucial role in biotic and abiotic stresses. In our previous study, five 13-LOX genes of oriental melon were regulated by abiotic stress but it is unclear whether the 9-LOX is involved in biotic and abiotic stresses. The promoter analysis revealed that CmLOX09 (type of 9-LOX) has hormone elements, signal substances, and stress elements. We analyzed the expression of CmLOX09 and its downstream genes-CmHPL and CmAOS-in the leaves of four-leaf stage seedlings of the oriental melon cultivar "Yumeiren" under wound, hormone, and signal substances. CmLOX09, CmHPL, and CmAOS were all induced by wounding. CmLOX09 was induced by auxin (indole acetic acid, IAA) and gibberellins (GA); however, CmHPL and CmAOS showed differential responses to IAA and GA. CmLOX09, CmHPL, and CmAOS were all induced by hydrogen peroxide (HO) and methyl jasmonate (MeJA), while being inhibited by abscisic acid (ABA) and salicylic acid (SA). CmLOX09, CmHPL, and CmAOS were all induced by the powdery mildew pathogen Podosphaera xanthii. The content of 2-hexynol and 2-hexenal in leaves after MeJA treatment was significantly higher than that in the control. After infection with P. xanthii, the diseased leaves of the oriental melon were divided into four levels-levels 1, 2, 3, and 4. The content of jasmonic acid (JA) in the leaves of levels 1 and 3 was significantly higher than that in the level 0 leaves. In summary, the results suggested that CmLOX09 might play a positive role in the response to MeJA through the hydroperoxide lyase (HPL) pathway to produce C6 alcohols and aldehydes, and in the response to P. xanthii through the allene oxide synthase (AOS) pathway to form JA.
在植物中，脂氧合酶（LOXs）在生物和非生物胁迫中起着至关重要的作用。在我们之前的研究中，东方甜瓜的五个 13-LOX 基因受非生物胁迫调节，但 9-LOX 是否参与生物和非生物胁迫尚不清楚。启动子分析表明，CmLOX09（9-LOX 类型）具有激素元件、信号物质和应激元件。我们分析了在激素和信号物质存在的情况下，东方甜瓜‘Yumeiren’四叶期幼苗叶片中 CmLOX09 及其下游基因 CmHPL 和 CmAOS 的表达。CmLOX09、CmHPL 和 CmAOS 均受创伤诱导。CmLOX09 受生长素（吲哚乙酸，IAA）和赤霉素（GA）诱导；然而，CmHPL 和 CmAOS 对 IAA 和 GA 的反应不同。CmLOX09、CmHPL 和 CmAOS 均受过氧化氢（HO）和茉莉酸甲酯（MeJA）诱导，同时受脱落酸（ABA）和水杨酸（SA）抑制。CmLOX09、CmHPL 和 CmAOS 均受白粉病病原菌 Podosphaera xanthii 诱导。用 MeJA 处理后叶片中 2-己炔醇和 2-己烯醛的含量明显高于对照。感染 P. xanthii 后，东方甜瓜病叶分为四级-1 级、2 级、3 级和 4 级。1 级和 3 级叶片中茉莉酸（JA）的含量明显高于 0 级叶片。综上所述，结果表明，CmLOX09 可能通过过氧化氢酶（HPL）途径产生 C6 醇和醛，通过丙二烯氧化物合酶（AOS）途径形成 JA，从而在对 MeJA 的反应中发挥积极作用，在对 P. xanthii 的反应中也发挥积极作用。
