Phytomelatonin receptor PMTR1 is crucial for melatonin-mediated plant broad-spectrum disease resistance

PMTR1 is essential for melatonin-improved plant broad-spectrum disease resistance to bacterial pathogens and viruses. Melatonin plays vital roles in various plant stress responses, and the identification of phytomelatonin receptor 1 (PMTR1) in recent decades further extends the phytomelatonin signaling pathway. However, whether and how PMTR1 participates in plant broad-spectrum disease resistance has remained unclear. Here, we confirmed that exogenous melatonin enhanced disease resistance to bacterial blight and mosaic disease, indicating the crucial role of melatonin in cassava broad-spectrum disease resistance. In addition, the transcription of MePMTR1 was induced by Xanthomonas axonopodis pv. manihotis (Xam), common mosaic virus (CMV) and exogenous melatonin, suggesting that MePMTR1 may be involved in cassava immunity. Further investigation illustrated that MePMTR1 was a positive regulator in disease resistance to Xam and CMV, and it was necessary for melatonin-improved broad-spectrum disease resistance to the bacterial pathogen and the virus. Moreover, RNA-sequencing identified many differentially expressed genes (DEGs) in melatonin-improved disease resistance through MePMTR1, including calmodulin-like proteins (CMLs), calmodulin-binding proteins (CaMBPs), transcription factors WRKYs and MYBs, respiratory burst oxidase homolog protein C (RBOHC), heat shock protein 20, pathogenesis-related protein (PR10), etc. In total, this study provides new light on the theoretical foundation of melatonin in modulating broad-spectrum disease resistance in cassava, extending the understanding of the melatonin signaling pathway in plant immunity.