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.

薄皮甜瓜9-脂氧合酶(9-LOX)类型的CmLOX09对逆境、激素和信号类物质的响应

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[55]List of electronic supplementary materials

[56]Fig. S1 Cis-regulatory elements analysis of CmLOX09 promoter

[57]Fig. S2 Level of JA in oriental melon leaves after inoculation with Podosphaera xanthii analyzed with HPLC-MS/MS

[58]Table S1 Emission of GLVs in control and MeJA treatment leaves at 6, 72, and 168 h