Maize nicotinate <i>N</i>‐methyltransferase interacts with the NLR protein Rp1‐D21 and modulates the hypersensitive response
Mengjie Liu, Yajie Li, Yu‐Xiu Zhu, Yang Sun, Guan‐Feng Wang
Abstract
Abstract Most plant intracellular immune receptors belong to nucleotide‐binding, leucine‐rich repeat (NLR) proteins. The recognition between NLRs and their corresponding pathogen effectors often triggers a hypersensitive response (HR) at the pathogen infection sites. The nicotinate N ‐methyltransferase (NA N MT) is responsible for the conversion of nicotinate to trigonelline in plants. However, the role of NA N MT in plant defence response is unknown. In this study, we demonstrated that the maize ZmNA N MT, but not its close homolog ZmCOMT, an enzyme in the lignin biosynthesis pathway, suppresses the HR mediated by the autoactive NLR protein Rp1‐D21 and its N‐terminal coiled‐coil signalling domain (CC D21 ). ZmNA N MT, but not ZmCOMT, interacts with CC D21 , and they form a complex with HCT1806 and CCoAOMT2, two key enzymes in lignin biosynthesis, which can also suppress the autoactive HR mediated by Rp1‐D21. ZmNA N MT is mainly localized in the cytoplasm and nucleus, and either localization is important for suppressing the HR phenotype. These results lay the foundation for further elucidating the molecular mechanism of NA N MTs in plant disease resistance.