Department of Biochemistry, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic.
Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
J Exp Bot. 2021 Apr 2;72(8):3219-3234. doi: 10.1093/jxb/erab011.
Successful plant defence against microbial pathogens is based on early recognition and fast activation of inducible responses. Key mechanisms include detection of microbe-associated molecular patterns by membrane-localized pattern recognition receptors that induce a basal resistance response. A well-described model of such responses to pathogens involves the interactions between Solanaceae plants and proteinaceous elicitors secreted by oomycetes, called elicitins. It has been hypothesized that the formation of oligomeric structures by elicitins could be involved in their recognition and activation of defensive transduction cascades. In this study, we tested this hypothesis using several approaches, and we observed differences in tobacco plant responses induced by the elicitin β-cryptogein (β-CRY) and its homodimer, β-CRYDIM. We also found that the C-terminal domain of elicitins of other ELI (true-elicitin) clades plays a significant role in stabilization of their oligomeric structure and restraint in the cell wall. In addition, covalently cross-linking β-CRYDIM impaired the formation of signalling complexes, thereby reducing its capacity to elicit the hypersensitive response and resistance in the host plant, with no significant changes in pathogenesis-related protein expression. By revealing the details of the effects of β-CRY dimerization on recognition and defence responses in tobacco, our results shed light on the poorly understood role of elicitins' oligomeric structures in the interactions between oomycetes and plants.
成功的植物防御微生物病原体的基础是早期识别和快速激活可诱导的反应。关键机制包括通过膜定位的模式识别受体检测微生物相关的分子模式，从而诱导基础抗性反应。这种对病原体的反应的一个很好的描述性模型涉及茄科植物与卵菌分泌的蛋白激发子（称为激发素）之间的相互作用。有人假设，激发素形成寡聚体结构可能与其识别和激活防御转导级联有关。在这项研究中，我们使用了几种方法来检验这一假设，观察到由激发素β-隐地蛋白（β-CRY）及其同源二聚体β-CRYDIM 诱导的烟草植物反应的差异。我们还发现，其他 ELI（真激发素）类群的激发素的 C 末端结构域在稳定其寡聚体结构和限制在细胞壁中的方面发挥着重要作用。此外，β-CRYDIM 的共价交联破坏了信号复合物的形成，从而降低了其在宿主植物中引发过敏反应和抗性的能力，而与病程相关蛋白的表达没有明显变化。通过揭示 β-CRY 二聚化对烟草中识别和防御反应的影响细节，我们的结果阐明了激发素寡聚体结构在卵菌与植物相互作用中的作用，这一作用目前仍知之甚少。
