Melatonin Relieves Ozone Stress in Grape Leaves by Inhibiting Ethylene Biosynthesis
Chuang Liu, Hui Kang, Yafang Wang, Yuxin Yao, Zhen Gao, Yuanpeng Du
Abstract
Ozone (O 3 ) stress severely affects the normal growth of grape ( Vitis vinifera L.) leaves. Melatonin (MT) plays a significant role in plant response to various abiotic stresses, but its role in O 3 stress and related mechanisms are poorly understood. In order to understand the mechanism of MT in alleviate O 3 stress in grape leaves, we perform a transcriptome analyses of grapes leaves under O 3 stress with or without MT treatment. Transcriptome analysis showed that the processes of ethylene biosynthesis and signaling were clearly changed in “Cabernet Sauvignon” grapes under O 3 and MT treatment. O 3 stress induced the expression of genes related to ethylene biosynthesis and signal transduction, while MT treatment significantly inhibited the ethylene response mediated by O 3 stress. Further experiments showed that both MT and aminoethoxyvinylglycine (AVG, an inhibitor of ethylene biosynthesis) enhanced the photosynthetic and antioxidant capacities of grape leaves under O 3 stress, while ethephon inhibited those capacities. The combined treatment effect of MT and ethylene inhibitor was similar to that of MT alone. Exogenous MT reduced ethylene production in grape leaves under O 3 stress, while ethephon and ethylene inhibitors had little effect on the MT content of grape leaves after O 3 stress. However, overexpression of VvACO2 ( 1-aminocyclopropane-1-carboxylate oxidase2 ) in grape leaves endogenously induced ethylene accumulation and aggravated O 3 stress. Overexpression of the MT synthesis gene VvASMT1 ( acetylserotonin methyltransferase1 ) in tobacco ( Nicotiana tabacum L.) alleviated O 3 stress and reduced ethylene biosynthesis after O 3 stress. In summary, MT can alleviate O 3 stress in grape leaves by inhibiting ethylene biosynthesis.