The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, China.
The Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao, China.
Mol Plant Pathol. 2021 May;22(5):564-579. doi: 10.1111/mpp.13044. Epub 2021 Mar 6.
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 (NANMT) is responsible for the conversion of nicotinate to trigonelline in plants. However, the role of NANMT in plant defence response is unknown. In this study, we demonstrated that the maize ZmNANMT, 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 ). ZmNANMT, but not ZmCOMT, interacts with CC , 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. ZmNANMT 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 NANMTs in plant disease resistance.
大多数植物细胞内免疫受体属于核苷酸结合富含亮氨酸重复（NLR）蛋白。NLR 与其相应的病原体效应物之间的识别通常会在病原体感染部位引发过敏反应（HR）。烟酸 N-甲基转移酶（NANMT）负责将烟酸转化为植物中的瓜氨酸。然而，NANMT 在植物防御反应中的作用尚不清楚。在这项研究中，我们证明了玉米 ZmNANMT（而不是其紧密同源物 ZmCOMT，木质素生物合成途径中的一种酶）抑制由自身激活的 NLR 蛋白 Rp1-D21 及其 N 端卷曲螺旋信号结构域（CC ）介导的 HR。ZmNANMT 与 CC 相互作用，并与木质素生物合成的两个关键酶 HCT1806 和 CCoAOMT2 形成复合物，它们也可以抑制 Rp1-D21 介导的自身激活 HR。ZmNANMT 主要定位于细胞质和细胞核中，这两种定位对于抑制 HR 表型都很重要。这些结果为进一步阐明 NANMT 在植物抗病性中的分子机制奠定了基础。
