Pear anthracnose, caused by the fungus Colletotrichum fructicola, is a devastating disease for the pear industry. The apoplast, an extracellular compartment outside the plasma membrane, plays a crucial role in water and nutrient transport, as well as plant-microbe interactions. This study aimed to uncover the molecular mechanism of pear leaf apoplastic protein-mediated resistance to C. fructicola. Apoplast fluid was isolated using the vacuum infiltration method, and defence-related apoplastic proteins were identified through protein mass spectrometry and transcriptome sequencing. We found 213 apoplastic proteins in the leaf apoplast fluid during early C. fructicola infection, with the majority (74.64%) being enzymes, including glycosidases, proteases, and oxidoreductases. Gene Ontology analysis revealed their involvement in defence response, enzyme inhibition, carbohydrate metabolism, and phenylpropanoid biosynthesis. Transcriptome analysis showed the infection induced expression of certain apoplast proteins, potentially contributing to pear leaf resistance. Notably, the expression of PbrGlu1, an endo-β-1,3-glucanase from the glycoside hydrolase 17 family, was significantly higher in infected leaves. Silencing of the PbrGlu1 gene increased pear leaf susceptibility to C. fructicola, leading to more severe symptoms and higher reactive oxygen species content. Overall, our study provides insights into the apoplast space interaction between pear leaves and C. fructicola, identifies a key gene in infected pears, and offers a foundation and new strategy for understanding the molecular mechanisms underlying pear anthracnose and breeding disease-resistant pears.

梨炭疽病是由真菌Colletotrichum fructicola引起的，对梨产业来说是一种毁灭性的疾病。质外体是质膜外的细胞外区室，在水和养分运输以及植物-微生物相互作用中发挥着至关重要的作用。本研究旨在揭示梨叶质外体蛋白介导的果果梨抗性的分子机制。采用真空渗透法分离质外体液，并通过蛋白质质谱和转录组测序鉴定与防御相关的质外体蛋白。我们在早期C. fructicola感染过程中，在叶片质外体液中发现了 213 种质外体蛋白，其中大多数（74.64%）是酶，包括糖苷酶、蛋白酶和氧化还原酶。基因本体分析揭示了它们参与防御反应、酶抑制、碳水化合物代谢和苯丙素生物合成。转录组分析表明，感染诱导某些质外体蛋白的表达，可能有助于梨叶的抗性。值得注意的是， PbrGlu1（一种来自糖苷水解酶 17 家族的内切-β-1,3-葡聚糖酶）的表达在受感染的叶子中显着升高。 PbrGlu1基因的沉默增加了梨叶对C. fructicola的敏感性，导致更严重的症状和更高的活性氧含量。总体而言，我们的研究提供了对梨叶和C. fructicola之间的质外体空间相互作用的见解，确定了受感染梨中的关键基因，并为了解梨炭疽病和培育抗病梨的分子机制提供了基础和新策略。