Ao Kevin, Rohmann Philipp F W, Huang Shuai, Li Lin, Lipka Volker, Chen She, Wiermer Marcel, Li Xin
Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
Plant J. 2023 May;114(3):591-612. doi: 10.1111/tpj.16155. Epub 2023 Mar 22.
Immune receptors play important roles in the perception of pathogens and initiation of immune responses in both plants and animals. Intracellular nucleotide-binding domain leucine-rich repeat (NLR)-type receptors constitute a major class of receptors in vascular plants. In the Arabidopsis thaliana mutant suppressor of npr1-1, constitutive 1 (snc1), a gain-of-function mutation in the NLR gene SNC1 leads to SNC1 overaccumulation and constitutive activation of defense responses. From a CRISPR/Cas9-based reverse genetics screen in the snc1 autoimmune background, we identified that mutations in TRAF CANDIDATE 1b (TC1b), a gene encoding a protein with four tumor necrosis factor receptor-associated factor (TRAF) domains, can suppress snc1 phenotypes. TC1b does not appear to be a general immune regulator as it is not required for defense mediated by other tested immune receptors. TC1b also does not physically associate with SNC1, affect SNC1 accumulation, or affect signaling of the downstream helper NLRs represented by ACTIVATED DISEASE RESISTANCE PROTEIN 1-L2 (ADR1-L2), suggesting that TC1b impacts snc1 autoimmunity in a unique way. TC1b can form oligomers and localizes to punctate structures of unknown function. The puncta localization of TC1b strictly requires its coiled-coil (CC) domain, whereas the functionality of TC1b requires the four TRAF domains in addition to the CC. Overall, we uncovered the TRAF domain protein TC1b as a novel positive contributor to plant immunity.
免疫受体在植物和动物感知病原体及启动免疫反应过程中发挥着重要作用。细胞内核苷酸结合结构域富含亮氨酸重复序列（NLR）型受体是维管植物中主要的受体类型。在拟南芥突变体npr1-1组成型1（snc1）抑制子中，NLR基因SNC1的功能获得性突变导致SNC1过度积累以及防御反应的组成型激活。通过基于CRISPR/Cas9的反向遗传学筛选，在snc1自身免疫背景下，我们发现肿瘤坏死因子受体相关因子候选蛋白1b（TC1b）发生突变可以抑制snc1的表型，TC1b基因编码一种含有四个肿瘤坏死因子受体相关因子（TRAF）结构域的蛋白。TC1b似乎不是一个普遍的免疫调节因子，因为其他测试的免疫受体介导的防御反应不需要它。TC1b也不与SNC1发生物理相互作用、不影响SNC1的积累，也不影响由激活的抗病蛋白1-L2（ADR1-L2）代表的下游辅助NLR的信号传导，这表明TC1b以独特的方式影响snc1自身免疫。TC1b可以形成寡聚体并定位于功能未知的点状结构。TC1b的点状定位严格需要其卷曲螺旋（CC）结构域，而TC1b的功能除了CC结构域外还需要四个TRAF结构域。总体而言，我们发现TRAF结构域蛋白TC1b是植物免疫的一个新的正向贡献因子。
