A PAMP ‐Inducible Caffeic Acid O ‐Methyltransferase Gene ( EcCOMT49

ABSTRACT

Caffeic acid O ‐methyltransferases (COMTs) contribute to phenylpropanoid metabolism and have emerging roles in reactive oxygen species (ROS) regulation during plant stress. Finger millet ( Eleusine coracana ), a resilient cereal, harbours diverse COMT isoforms, although their functional contribution to immunity remains largely unexplored. Here, we investigated the role of the PAMP‐responsive gene EcCOMT49 in regulating plant defence and ROS homeostasis. Promoter‐GUS reporter analysis showed that the PAMPs flg22 and chitin significantly induce the EcCOMT49 promoter as evidenced by strong GUS staining compared with untreated controls, indicating strong PAMP‐inducible transcriptional activity. EcCOMT49 exhibits strong flg22 and chitin‐induced transcriptional upregulation, with its protein localising to both cytosol and nucleus. Transient expression in Nicotiana benthamiana revealed that EcCOMT49 suppresses Bax‐induced programmed cell death (PCD) and limits associated ROS accumulation, as shown by reduced DAB and NBT staining. Moreover, EcCOMT49 expression improves tolerance to the necrotrophic fungus Sclerotinia sclerotiorum , limiting both lesion expansion and ROS accumulation throughout infection. Together, these findings suggest that EcCOMT49 may function as a modulatory factor in biotic stress tolerance that acts by limiting ROS‐associated cell death. The observed PAMP‐responsive promoter activity supports a potential role of EcCOMT49 in plant defence responses, although its precise regulatory mechanisms remain to be elucidated.