受体类蛋白是由胞外亮氨酸富集重复序列、单跨膜区以及短的胞内区构成的植物免疫反应受体。
9月14日，北京生命科学研究所张跃林研究小组发现一个免疫反应组成型激活的获得功能型突变体snc2-1D (suppressor of npr1-1, constitutive 2)。该研究成果发表于最新一期Plant Cell杂志上。
图位克隆发现突变基因编码了一个受体类蛋白。在snc2-1D 中，跨膜区GXXXG motif的第二个Gly变成Arg，提示我们这个氨基酸对蛋白功能的负调控起到重要作用。上下位遗传分析表明snc2-1D激活了一条不同于NB-LRR类R蛋白介导的免疫反应通路。对snc2-1D 进行抑制子筛选，发现转录因子WRKY70 的突变能抑制snc2-1D激活的免疫反应，说明WRKY70在snc2-1D 的下游发挥功能。先前在拟南芥中没有研究受体类蛋白介导的免疫反应的平台，snc2-1D的发现成为我们研究受体类蛋白免疫通路的出发点。
博士生张亚晰为本文的第一作者，参与此工作的还有中国农业大学的杨元爱, 北京师范大学的方斌和丁平涛, University of British Columbia的Patrick Gannon和李昕教授。我所研究员张跃林博士是本文的通讯作者。此项研究为科技部863和北京市科委资助课题，在北京生命科学研究所完成。
生物谷推荐英文摘要：
Plant Cell DOI:10.1105/tpc.110.074120
Arabidopsis snc2-1D Activates Receptor-Like Protein-Mediated Immunity Transduced through WRKY70
Yaxi Zhanga,b, Yuanai Yanga, Bin Fanga, Patrick Gannonc, Pingtao Dinga, Xin Lic and Yuelin Zhanga,1
a National Institute of Biological Sciences, Beijing 102206, People’s Republic of China
b Beijing Normal University, Beijing 100875, People's Republic of China
c Michael Smith Laboratories, University of British Columbia, Vancouver V6T 1Z4, Canada
Plant immune receptors belonging to the receptor-like protein (RLP) family contain extracellular leucine-rich repeats (LRRs) and a short cytoplasmic tail linked by a single transmembrane motif. Here, we report the identification of snc2-1D (for suppressor of npr1-1, constitutive 2), a semidominant Arabidopsis thaliana mutant with constitutively activated defense responses. Map-based cloning of snc2-1D showed that it encodes an RLP. The point mutation in snc2-1D leads to substitution of the second Gly for Arg in the conserved GXXXG motif of the transmembrane helix, suggesting that this residue is important for negative regulation of the protein. Epistasis analysis revealed that the snc2-1D mutant phenotype is not affected by mutations in genes known to be required for the nucleotide binding (NB)-LRR Resistance (R) protein signaling. A suppressor screen of snc2-1D was performed, and map-based cloning of one suppressor revealed that mutations in WRKY70 suppress the constitutive defense responses in snc2-1D, suggesting that WRKY70 functions downstream of snc2-1D. The identification of snc2-1D provides us with a unique system for genetic analysis of resistance pathways downstream of RLPs, which may be distinct from those downstream of NB-LRR type R proteins.
