近日，美国科罗拉多州立大学、北卡罗来纳大学和华盛顿大学的研究人员合作取得一项新进展。他们发现植物免疫受体的TIR结构域是促进细胞死亡的NAD+裂解酶。该项研究成果发表在2019年8月23日出版的《科学》上。
研究人员证明NLR的植物Toll /白细胞介素-1受体（TIR）结构域是能够以其氧化形式（NAD+）降解烟酰胺腺嘌呤二核苷酸的酶。植物TIR结构域的细胞死亡诱导和NAD+切割活性都需要已知的自结合界面和假定的催化谷氨酸，这个位点在细菌TIR NAD +切割酶（NADases）和哺乳动物SARM1（sterile alpha and TIR motif containing 1）中都是保守的。研究人员鉴定到一个环磷酸二磷酸核糖的变体可作为TIR酶活性的生物标志物。TIR酶活性由病原体识别所诱导，并在EDS1（enhanced disease susceptibility 1）和NRG1（N requirement gene 1）的上游发挥功能，这两个基因编码TIR免疫功能所需的调节蛋白。因此，植物TIR-NLR受体需要NADase功能来将病原体识别转化为细胞死亡反应。
据了解，植物NLR（nucleotide-binding leucine-rich repeat）免疫受体通过未知机制激活细胞死亡并赋予疾病抗性。
附：英文原文
Title: TIR domains of plant immune receptors are NAD+-cleaving enzymes that promote cell death
Author: Li Wan, Kow Essuman, Ryan G. Anderson, Yo Sasaki, Freddy Monteiro, Eui-Hwan Chung, Erin Osborne Nishimura, Aaron DiAntonio, Jeffrey Milbrandt, Jeffery L. Dangl, Marc T. Nishimura
Issue&Volume: Volume 365 Issue 6455
Abstract: Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors activate cell death and confer disease resistance by unknown mechanisms. We demonstrate that plant Toll/interleukin-1 receptor (TIR) domains of NLRs are enzymes capable of degrading nicotinamide adenine dinucleotide in its oxidized form (NAD+). Both cell death induction and NAD+ cleavage activity of plant TIR domains require known self-association interfaces and a putative catalytic glutamic acid that is conserved in both bacterial TIR NAD+-cleaving enzymes (NADases) and the mammalian SARM1 (sterile alpha and TIR motif containing 1) NADase. We identify a variant of cyclic adenosine diphosphate ribose as a biomarker of TIR enzymatic activity. TIR enzymatic activity is induced by pathogen recognition and functions upstream of the genes enhanced disease susceptibility 1 (EDS1) and N requirement gene 1 (NRG1), which encode regulators required for TIR immune function. Thus, plant TIR-NLR receptors require NADase function to transduce recognition of pathogens into a cell death response.
DOI: 10.1126/science.aax1771
Source:https://science.sciencemag.org/content/365/6455/799