Defended to the Nines: 25 years of Resistance Gene Cloning Identifies Nine Mechanisms for R Protein Function

Plants have many, highly variable resistance (R) gene loci, which provide resistance to a variety of pathogens. The first R gene to be cloned, maize (Zea mays) Hm1, was published over 25 years ago, and since then, many different R genes have been identified and isolated. The encoded proteins have provided clues to the diverse molecular mechanisms underlying immunity. Here, we present a meta-analysis of 314 cloned R genes. The majority of R genes encode cell-surface or intracellular receptors, and we distinguish nine molecular mechanisms by which R proteins can elevate (提高) or trigger disease resistance: direct (1) or indirect (2) perception of pathogen-derived molecules on the cell surface by receptor-like proteins and receptor-like kinases; direct (3) or indirect (4) intracellular detection of pathogen-derived molecules by nucleotide-binding, leucine-rich repeat receptors, or detection through integrated domains (5); perception of transcription activator-like effectors through activation of executor genes (6); and active (7), passive (8), or host reprogramming mediated (9) loss-of-susceptibility. Although the molecular mechanisms underlying the functions of R genes are only understood for a small proportion of known R genes, a clearer understanding of mechanisms is emerging and will be crucial for rational (合理的) engineering and deployment of novel R genes.

植物有着许多高度可变的抗性R基因位点，这些R基因位点为植物提供针对多种病原菌的抗性。第一个被克隆的R基因是玉米中的Hm1，在25年前就已经报道，从那以后，很多不同的R基因被陆续鉴定和分离出来。这些R基因编码的蛋白为植物免疫潜在的分子机制提供了新的线索。本文对314个已经克隆的R基因进行了元分析。R基因主要编码了细胞表面受体和细胞内受体，作者通过R蛋白诱导疾病抗性的分子机制把R基因化为九大类：通过细胞表面上的类受体蛋白或类受体激酶直接（1）或者间接（2）感应来自于病原菌的分子；通过核酸结合、富含亮氨酸重复受体直接（3）或者间接（4）检测细胞内的来自于病原菌的分子，或者通过整合的结构域检测（5）；通过激活下游功能基因感知转录激活效应物（6）；主动（7），被动（8），或者是寄主重编程介导的（9）病原菌易感性缺失。尽管现在只是对部分的已知R基因功能有了解，对于R基因分子机制的研究越来越透彻，这对于将来开发和利用这些R基因至关重要。

通讯：Renier A. L. van der Hoorn (https://www.plants.ox.ac.uk/people/renier-van-der-hoorn)

研究方向：植物病原菌的寄主调控。

doi: https://doi.org/10.1105/tpc.17.00579