An oriental melon 9-lipoxygenase gene CmLOX09 response to stresses, hormones, and signal substances

Abstract

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 (GA₃); however, CmHPL and CmAOS showed differential responses to IAA and GA₃. CmLOX09, CmHPL, and CmAOS were all induced by hydrogen peroxide (H₂O₂) 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.

Alternate abstract:

中文概要

目的

研究CmLOX09及其下游基因CmHPL和CmAOS 对逆境、激素和信号类物质的响应,进一步测定茉莉酸甲酯(MeJA)处理后叶片中绿叶挥发物的含量以及接种白粉病菌后叶片中茉莉酸含量的逆境、激素和信号类物质的响应,进一步测定 茉莉酸甲酯(MeJA)处理后叶片中绿叶挥发物的含量以及接种白粉病菌后叶片中茉莉酸含量的变化,探讨脂氧合酶(LOX)响应这两种胁迫的可能途径

创新点

通过对CmLOX09 启动子中顺式作用原件的分析预测,首次研究薄皮甜瓜9-LOX类型的CmLOX09 对机械损伤、激素、信号类物质以及生物胁迫的响应

方法

利用Plant CARE 软件对CmLOX09 启动子响应元 件进行预测分析(图S1);利用荧光定量聚合酶 链反应(qRT-PCR)技术分析甜瓜在机械损伤、激素、信号类物质以及生物胁迫处理后叶片中 CmLOX09、CmHPL 和CmAOS 的表达模式;利用 气相色谱-质谱连用仪(GC-MS)测定叶片中绿 叶挥发物的含量(图4);利用高效液相色谱- 串联质谱法(HPLC-MS/MS)分析和测定叶片中 茉莉酸的含量(图6)。

结论

本研究结果显示:CmLOX09 参与机械损伤、激 素、信号类物质及白粉病菌的防御反应(图1~3, 5)。9-LOX 类型的CmLOX09 可能通过氢过氧化 物裂解酶(HPL)途径产生的绿叶挥发物(GLV) 来响应MeJA(图4),并通过丙二烯合酶(AOS) 途径产生的茉莉酸来响应真菌胁迫(图6)。综 上所述,9-LOX 类型的CmLOX09 可能在生物和 非生物胁迫反应中起重要作用。