Abstract
Drought stress severely impairs plant growth and production. Lipoxygenase (LOX), a master regulator for lipid peroxidation, is critical for direct or indirect response to abiotic stresses. Here, we found that drought stress induced the transcription of CmLOX10 in leaves of oriental melon seedlings. Reverse genetic approaches and physiological analyses revealed that silencing CmLOX10 increased drought susceptibility and stomatal aperture in oriental melon seedlings, and that ectopic overexpression of CmLOX10 in Arabidopsis enhanced drought tolerance and decreased the stomatal aperture. Moreover, the transcription of jasmonic acid (JA)-related genes and JA accumulation were significantly induced in CmLOX10-overexpressed Arabidopsis, which were reversely suppressed in CmLOX10-silenced seedlings during the stage of drought stress. Foliar application of JA further verified that JA enhanced drought tolerance and induced stomatal closure in leaves of melon seedlings. In addition, the feedback regulation of CmLOX10 was induced by JA signaling, and the expression level of CmMYC2 was increased by JA and drought treatment. Yeast one-hybrid analysis showed that CmMYC2 directly bound to the promoter of CmLOX10. In summary, we identified the important roles of CmLOX10 in the regulation of drought tolerance in oriental melon seedlings through JA- mediated stomatal closure and JA signaling-mediated feedback through CmMYC2.
Highlights
Drought stress is a major environmental stress that severely impairs plant growth and development, even leading to a serious loss in crops yield[1]
We were interested in characterizing the role of CmLOXs in response to drought stress. qRT–PCR analysis has shown that the transcription of CmLOX10, CmLOX11, CmLOX12, CmLOX13, and CmLOX18 in oriental melon leaves were strongly induced by 8% PEG6000 treatment, while the expressions of CmLOX02, CmLOX05 and CmLOX06 were almost unchanged, and the other CmLOXs were slightly up-regulated by 8% PEG6000 treatment (Fig. 1)
We found that CmLOX10 gene, a 13-LOX gene induced by abiotic and hormonal stresses in oriental melon 30, was quickly and strongly induced by drought stress (Fig. 1)
Summary
Drought stress is a major environmental stress that severely impairs plant growth and development, even leading to a serious loss in crops yield[1]. Numerous studies suggested JA plays an important role in response to abiotic stresses. Drought stress induced the accumulation of JA 9 in plants, JA enhanced drought stress mainly through regulating stomatal closure and transpirational water loss 10–13. LOXs play key roles in all kinds of plant physiology process including growth and development 17,18, senescence 19, and especially responses to biotic and abiotic stresses 20. Pepper CaLOX1 and persimmon DkLOX3, belonging to 9-LOX genes, responded to drought and high salinity stress by modulating the expression of ABA- and stress-responsive genes, lipid peroxidation and ROS accumulation in Arabidopsis 21,22. Numerous studies suggested that 13-LOX genes were mainly involved in the response of plants to biotic and abiotic stresses by regulating JA synthesis. MYC2 was found to bind to LOX2/3/4, AOS, and OPR327,28 according to the ChIPqPCR and ChIP-seq analyses
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