Division of Plant Biology, Bose Institute, Centenary Campus, P-1/12, CIT Scheme-VIIM, Kankurgachi, Kolkata 700054, West Bengal, India.
Centre of Excellence in Bioinformatics, Bose Institute, Centenary Campus, P-1/12, CIT Scheme-VIIM, Kankurgachi, Kolkata 700054, West Bengal, India.
Plant Sci. 2018 Nov;276:111-133. doi: 10.1016/j.plantsci.2018.08.008. Epub 2018 Aug 22.
Fusarium wilt is one of the most serious diseases affecting chickpea (Cicer arietinum L.). Here, we identified a putative Resistance Gene Analog (CaRGA) from chickpea, encoding a coiled-coil (CC) nucleotide-binding oligomerization domain (NB-ARC) containing leucine-rich repeat (LRR) protein (CC-NLR protein) that confers resistance against Fusarium oxysporum f. sp. ciceri race1 (Foc1). Over-expression and silencing of CaRGA in chickpea resulted in enhanced resistance and hyper-susceptibility, respectively against Foc1. Furthermore, defense response to Foc1 depends on CC-NLR interaction with WRKY64 transcription factor. CaRGA mediated wilt resistance largely compromised when WRKY64 was silenced. We also determined in planta intramolecular interactions and self-association of chickpea CC-NLR protein. The study shows CC domain suppressing auto-activation of the full-length CC-NLR protein in the absence of pathogen through self-inhibitory intramolecular interaction with NB-ARC domain, which is attenuated by self-interactions to LRR domain. Chickpea CC-NLR protein forms homocomplexes and then interacts with WRKY64. CC-NLR protein further phosphorylates WRKY64 thereby, ubiquitination and proteasome mediated degradation are protected. Phosphorylated WRKY64 with increased stability binds to EDS1 promoter and stimulates its transcription that induces in planta ectopic cell-death. The detailed analysis of CC-NLR and WRKY interactions provide a better understanding of the immune regulation by NLR proteins under biotic stresses.
枯萎病是影响鹰嘴豆（Cicer arietinum L.）的最严重病害之一。在这里，我们从鹰嘴豆中鉴定出一个假定的抗性基因类似物（CaRGA），该基因编码一个卷曲螺旋（CC）核苷酸结合寡聚化结构域（NB-ARC），包含富含亮氨酸重复（LRR）的蛋白（CC-NLR 蛋白），该蛋白赋予对尖孢镰刀菌 f. 种. 小种 1（Foc1）的抗性。在鹰嘴豆中过表达和沉默 CaRGA 分别导致对 Foc1 的增强抗性和超敏性。此外，对 Foc1 的防御反应依赖于 CC-NLR 与 WRKY64 转录因子的相互作用。当沉默 WRKY64 时，CaRGA 介导的枯萎病抗性在很大程度上受到损害。我们还确定了鹰嘴豆 CC-NLR 蛋白在体内的分子内相互作用和自组装。该研究表明，CC 结构域通过与 NB-ARC 结构域的自身抑制性分子内相互作用，在没有病原体的情况下抑制全长 CC-NLR 蛋白的自动激活，这种自相互作用被 LRR 结构域减弱。鹰嘴豆 CC-NLR 蛋白形成同源复合物，然后与 WRKY64 相互作用。CC-NLR 蛋白进一步使 WRKY64 磷酸化，从而保护其泛素化和蛋白酶体介导的降解。稳定性增加的磷酸化 WRKY64 与 EDS1 启动子结合并刺激其转录，从而诱导体内异位细胞死亡。对 CC-NLR 和 WRKY 相互作用的详细分析提供了对生物胁迫下 NLR 蛋白免疫调节的更好理解。
