The gray mold fungus is a necrotrophic pathogen that causes diseases in hundreds of plant species, including high-value crops. Its polyxenous nature and pathogenic success are due to its ability to perceive host signals in its favor. In this study, we found that laticifer cells of are a source of susceptibility factors required by to cause disease. Consequently, poor-in-latex () mutants, which lack laticifer cells, show full resistance to this pathogen, whereas -- mutants, which produce more laticifer cells, are hypersusceptible. These S factors are triterpenoid saponins, which are widely distributed natural products of vast structural diversity. The downregulation of laticifer-specific genes, which encode the first committed step enzymes for triterpene and, therefore, saponin biosynthesis, conferred disease resistance to . Likewise, the mutant, compromised in triterpenoid saponin biosynthesis, showed enhanced resistance. Interestingly, the application of different purified triterpenoid saponins pharmacologically complemented the disease-resistant phenotype of and mutants and enhanced disease susceptibility in different plant species. We found that triterpenoid saponins function as plant cues that signal transcriptional reprogramming in , leading to a change in its growth habit and infection strategy, culminating in the abundant formation of infection cushions, the multicellular appressoria apparatus dedicated to plant penetration and biomass destruction in . Taken together, these results provide an explanation for how plant triterpenoid saponins function as disease susceptibility factors to promote pathogenicity.

中文翻译：

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植物三萜皂苷作为易感因子促进灰葡萄孢致病性


灰霉病菌是一种坏死营养型病原体，可导致数百种植物患病，其中包括高价值作物。它的多杂性和致病性成功是由于它能够感知有利于其的宿主信号。在这项研究中，我们发现乳管细胞是引起疾病所需的易感因子的来源。因此，缺乏乳胶细胞的“poor-in-latex”（）突变体对这种病原体表现出完全的抵抗力，而产生更多乳胶细胞的“-”突变体则高度敏感。这些S因子是三萜皂苷，是分布广泛、结构多样的天然产物。乳管特异性基因的下调赋予了抗病性，该基因编码三萜以及皂苷生物合成的第一个关键步骤酶。同样，三萜皂苷生物合成受损的突变体表现出增强的抵抗力。有趣的是，不同纯化三萜皂苷的应用在药理学上补充了突变体的抗病表型，并增强了不同植物物种的疾病易感性。我们发现三萜皂苷作为植物信号传导转录重编程信号，导致其生长习性和感染策略的改变，最终导致感染垫的丰富形成，感染垫是专门负责植物渗透和生物量破坏的多细胞附着胞。总而言之，这些结果解释了植物三萜皂苷如何作为疾病易感因子来促进致病性。