AUTHOR=Zhu Ying , Guo Miao-Jie , Song Jian-Bo , Zhang Shu-Yuan , Guo Rui , Hou Dai-Ru , Hao Cheng-Ying , An Hong-Li , Huang Xuan 

TITLE=Roles of Endogenous Melatonin in Resistance to Botrytis cinerea Infection in an Arabidopsis Model

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.683228

DOI=10.3389/fpls.2021.683228

ISSN=1664-462X

ABSTRACT=<p>Melatonin is an important bioactive molecule in plants. Two synthetases, N-acetylserotonin methyltransferase (ASMT) and serotonin N-acetyltransferase (SNAT) are involved in the final two steps of melatonin synthesis. Melatonin participates in responses to a variety of biotic and abiotic stresses in plants, but few studies have addressed the roles of endogenous melatonin in pathogen resistance. We investigated the role of endogenous melatonin in resistance to <italic>Botrytis cinerea</italic> infection in an <italic>Arabidopsis thaliana</italic> model system. Plant lines that overexpressed <italic>ASMT</italic> or <italic>SNAT</italic> through genetic manipulation showed upregulated expression of resistance genes <italic>PR1</italic> and <italic>PR5</italic>, transcription factor gene <italic>WRKY33</italic>, and jasmonic acid (JA) defense pathway marker gene <italic>PDF1.2</italic>, and downregulated transcription factor gene <italic>MYC2</italic> in JA signaling pathway. Higher melatonin content also enhanced the activity of antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD), increased JA content, reduced plant disease symptoms, and reduced lesion size in leaves. These findings indicate that endogenous melatonin enhances plant resistance to <italic>B. cinerea</italic> infection. In contrast, <italic>ASMT</italic> and <italic>SNAT</italic> gene silencing lines showed opposite results and were more susceptible to <italic>B. cinerea</italic>. Thus, it can be demonstrated that melatonin functions as an effective regulator of plant stress resistance at the genetic level. A schematic model is presented for its role in resistance to <italic>B. cinerea</italic> infection. Our findings also helped to elucidate the associated signal transduction pathways and interactions between melatonin and other plant hormones.</p>