Antifungal mechanism of volatile compounds emitted by Actinomycetota Paenarthrobacter ureafaciens from a disease-suppressive soil on Saccharomyces cerevisiae.

Increasing evidence suggests that in disease-suppressive soils, microbial volatile compounds (mVCs) released from bacteria may inhibit the growth of plant-pathogenic fungi. However, the antifungal activities and molecular responses of fungi to different mVCs remain largely undescribed. In this study, we first evaluated the responses of pathogenic fungi to treatment with mVCs from Paenarthrobacter ureafaciens. Then, we utilized the well-characterized fungal model organism Saccharomyces cerevisiae to study the potential mechanistic effects of the mVCs. Our data showed that exposure to P. ureafaciens mVCs leads to reduced growth of several pathogenic fungi, and in yeast cells, mVC exposure prompts the accumulation of reactive oxygen species (ROS). Further experiments with S. cerevisiae deletion mutants indicated that Slt2/Mpk1 and Hog1 MAPKs play major roles in the yeast response to P. ureafaciens mVCs. Transcriptomic analysis revealed that exposure to mVCs was associated with 1030 differentially expressed genes (DEGs) in the yeast. According to GO and KEGG analyses, many of these DEGs are involved in mitochondrial dysfunction, cell integrity, mitophagy, cellular metabolism and iron uptake. Genes encoding antimicrobial proteins were also significantly altered in the yeast after exposure to mVCs. These findings suggest that oxidative damage and mitochondrial dysfunction are major contributors to the fungal toxicity of mVCs. Furthermore, our data showed that cell wall defenses, antioxidant defenses and antimicrobial defenses are induced in yeast exposed to mVCs. Thus, our findings expand upon previous research by delineating the transcriptional responses of fungal model.越来越多的证据表明，在抑病土壤中，细菌释放的微生物挥发性化合物（microbial volatile compounds, mVCs）可抑制植物病原真菌的生长。然而，真菌针对不同mVCs的抗真菌活性及其分子响应机制在很大程度上仍未被解析。本研究首先评估了病原真菌对解脲节杆菌（Paenarthrobacter ureafaciens）释放的mVCs的响应；随后，采用研究已较为透彻的真菌模式生物酿酒酵母（Saccharomyces cerevisiae），探究该mVCs发挥作用的潜在分子机制。我们的实验数据显示，暴露于解脲节杆菌mVCs可显著抑制多种病原真菌的生长；在酵母细胞中，mVCs处理会诱导活性氧（reactive oxygen species, ROS）积累。进一步通过酿酒酵母缺失突变体开展的实验表明，Slt2/Mpk1与Hog1丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）在酵母响应解脲节杆菌mVCs的过程中发挥核心调控作用。转录组分析结果显示，经mVCs处理后，酵母中共存在1030个差异表达基因（differentially expressed genes, DEGs）。通过基因本体（Gene Ontology, GO）与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集分析发现，这些差异表达基因大多参与线粒体功能障碍、细胞完整性维持、线粒体自噬、细胞代谢及铁摄取等生物学过程。此外，编码抗菌蛋白的基因在mVCs处理后的酵母中也发生了显著表达变化。本研究结果表明，氧化损伤与线粒体功能障碍是mVCs产生真菌毒性的主要诱因。进一步的实验数据还显示，经mVCs处理的酵母会激活细胞壁防御、抗氧化防御及抗菌防御相关通路。综上，本研究阐明了真菌模式生物的转录响应机制，拓展了此前的相关研究领域。