Exogenous melatonin orchestrates multiple defense responses against Botrytis cinerea in tomato leaves
Zhenkai Xia,
Yule Ye,
Chenyang Hu,
Hao Wang,
Lingyun Zheng,
Yongxin Hu,
Li Sheng,
Jing Xing,
Wenxi Jia,
Yixi Wang,
Zhengrong Luo,
Xiaoli Sun,
Gengshou Xia,
Yan Zhang
Affiliations
Zhenkai Xia
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China; China Medical University -The Queen's University of Belfast Joint College, China Medical University, Shenyang, Liaoning, PR China
Yule Ye
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Chenyang Hu
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Hao Wang
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Lingyun Zheng
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Yongxin Hu
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Li Sheng
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Jing Xing
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Wenxi Jia
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Yixi Wang
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Zhengrong Luo
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Xiaoli Sun
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China
Gengshou Xia
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China; Corresponding author.
Yan Zhang
Department of Landscape and Horticulture, Ecology College, Lishui University, Lishui, Zhejiang, PR China; Corresponding author.
Infection of tomato leaves and fruits by necrotrophic fungal pathogen Botrytis cinerea causes considerable economic loss. Melatonin has multiple physiological functions and is considered a potential biocontrol agent for its positive effects on plant innate immunity. In tomato, melatonin reduces Botrytis-caused post-harvest fruit decay by activating jasmonic acid (JA) signaling. In this study, we analyzed the effects of melatonin on resistance to Botrytis and associated defense mechanisms in tomato leaves. Treatment of detached tomato leaves with melatonin at a concentration as low as 100 µM induced resistance to Botrytis based on reduced lesion size and fungal growth. Melatonin-induced resistance to gray mold was associated with activation of a complex set of defense mechanisms in tomato leaves. First, melatonin suppressed Botrytis-induced cell death and accumulation of reactive oxygen species (ROS), which was correlated with increased activities of ROS-scavenging enzymes and enhanced expression of their corresponding genes. Second, melatonin treatment induced callose synthase genes and promoted rapid and strong callose deposition in tomato leaves. Melatonin also induced other anti-microbial genes encoding chitinases, β-1,3-glucanases, phenylalanine ammonialyases and polyphenol oxidases. Third, melatonin increased Botrytis-induced expression of genes encoding SlWRKY33, SlMYC2 and SlERF transcription factors, which activate defense-related genes expression through JA and ethylene (ET) signaling pathways. By contrast, melatonin suppressed salicylic acid (SA) signaling based on reduced expression of the SlPR1 marker gene, which is known to antagonize defense against Botrytis. These results collectively indicate that exogenous melatonin orchestrates multiple signaling pathways to activate a complex set of defense mechanisms against Botrytis in tomato leaves.
