Molecular mechanisms of toxin-induced susceptibility and plant immunity-Functional diversification within the microbial NLP superfamily

寄主叶片坏死和乙烯诱导肽1样蛋白（NLP）是由植物病原微生物产生的三种微生物谱系：细菌，真菌和卵菌。许多NLP是成孔毒素，其在结合至真双子叶植物特异性鞘糖脂毒素受体后促进真双子叶植物的感染。鉴定缺乏溶细胞活性的NLP蛋白表明该微生物超家族内的功能多样化。编码非溶细胞NLP（ncNLP）的基因的表达模式和ncNLP与真菌凝集素的三级结构相似性表明，这些蛋白质可能在宿主感染的早期阶段在宿主附着中发挥作用。然而，没有证据表明ncNLP作为微生物毒力因子的作用。在这里，我们建议进行全面分析的推定的疾病促进活动的12个ncNLP从四个不同的微生物物种的瞬时表达在本氏烟草和随后的感染疫霉菌。我们进一步尝试研究一个建议的作用，ncNLPs凝集素样分子在早期宿主感染，并确定主机的目标结构ncNLPs。此外，我们设计了一种策略来控制寄生植物侵染茄科植物的条件，感染位点特异性表达的溶细胞NLP。

Host leaf necrosis and ethylene-inducing peptide 1-like proteins (NLP) are produced by plant pathogenic species from three microbial lineages; bacteria, fungi and oomycetes. Many NLPs are pore-forming toxins that facilitate infection of eudicot plants upon binding to eudicot-specific glycosphingolipid toxin receptors. Identification of NLP proteins lacking cytolytic activities suggests functional diversification within this microbial superfamily. Expression patterns of genes encoding non-cytolytic NLPs (ncNLPs) and tertiary structure similarities of ncNLPs with fungal lectins suggest that these proteins may play roles in host attachment at early phases of host infection. However, no evidence is available for a role of ncNLPs as microbial virulence factors. Here, we propose to conduct a comprehensive analysis of the putative disease-promoting activities of twelve ncNLPs from four different microbial species by transient expression in Nicotiana benthamiana and subsequent infection with Phytophthora infestans. We further attempt to study a proposed role of ncNLPs as lectin-like molecules during early host infection, and to identify host target structures for ncNLPs. In addition, we devise a strategy to control parasitic plant infestation in solanaceous plants by conditional, infection site-specific expression of a cytolytic NLP.