Melatonin signaling promotes resistance to rice sheath blight

Abstract

Rice sheath blight (ShB), caused by Rhizoctonia solani (R. solani) Kühn, is a significant disease that severely affects rice yield. Previous studies have indicated that melatonin significantly enhances plant resistance to various stressors, whereas its role in regulating ShB resistance remains unexplored. This study revealed that melatonin synthesis genes in rice were induced by R. solani infection. Genetic analysis revealed that overexpression of the melatonin biosynthetic gene SNAT1, encoding 5-hydroxytryptamine-N-acetyltransferase, led to high melatonin accumulation and enhanced rice resistance to ShB. Conversely, SNAT1/SNAT2 double-RNAi plants exhibited significantly reduced melatonin levels and increased susceptibility to ShB. Notably, exogenous melatonin treatment promoted rice resistance to ShB, and high melatonin concentrations inhibited the hyphal growth in R. solani. Furthermore, yeast one-hybrid screening identified the brassinosteroid signaling transcription factor brassinazole-resistant 1 (BZR1) as a direct activator of SNAT1 and SNAT2. Melatonin content was higher in the bzr1-D gain-of-function BZR1 mutant and lower in BZR1-RNAi plants than in wild-type controls. In addition, the bzr1-D mutant demonstrated increased rice resistance to ShB. These findings suggest that melatonin biosynthesis is upregulated in rice following R. solani infection, thereby improving resistance, and that BZR1 acts as a positive regulator to enhance melatonin biosynthesis and ShB resistance.

Keywords

BZR1 / melatonin / rice sheath blight / SNAT / transcriptional regulation

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2025 The Author(s). New Plant Protection published by John Wiley & Sons Australia, Ltd on behalf of Institute of Plant Protection, Chinese Academy of Agricultural Sciences.