Supplementary file 1_Functional characterization and mechanistic basis of antifungal and plant growth-promoting traits of Streptomyces sp. LZZY-S40.docx

Biological control agents (BCAs) represent a sustainable and environmentally benign alternative to synthetic chemical pesticides in modern agriculture. Among these, Streptomyces species are widely recognized for their ability to suppress phytopathogens and promote plant growth through diverse functional traits. In this study, a Streptomyces strain designated LZZY-S40 (=CGMCC No.30320) was evaluated for its antifungal activity using dual-culture assays and for its plant growth-promoting (PGP) potential through seedling growth assays and functional trait analysis. Genome mining and LC–MS-based metabolomic profiling were further performed to investigate its biosynthetic potential and secondary metabolite composition. Strain LZZY-S40 exhibited broad-spectrum antifungal activity against nine plant-pathogenic fungi, with inhibition rates ranging from 55.8% to 92.8%, the strongest suppression was observed against Exserohilum turcicum (92.8%). Further analyses indicated that strain LZZY-S40 is capable of producing extracellular proteases, suggesting a potential contribution to its antifungal activity. Genome mining identified several secondary metabolite biosynthetic gene clusters (BGCs) associated with the production of antimicrobial compounds, including those responsible for the biosynthesis of undecylprodigiosin and manumycin A. These genomic predictions were corroborated by LC-MS analysis. In addition to its antifungal properties, strain LZZY-S40 significantly enhanced the growth of wheat seedlings. At a concentration of 105 CFU·ml−1, it increased root length by 88.3%, shoot length by 37.9%, and fresh weight by 32.1%. Consistent with these phenotypic effects, the strain tested positive for multiple well-established PGP traits—including indole-3-acetic acid (IAA) production, siderophore secretion, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and nitrogenase-mediated nitrogen fixation—providing mechanistic support for its growth-enhancing capacity. Collectively, these findings demonstrate that strain LZZY-S40 exhibits robust antifungal activity against a broad spectrum of plant-pathogenic fungi and promotes plant growth significantly. Mechanistic investigations provided preliminary insights into the strain's antifungal and plant growth-promoting traits, contributing to a better understanding of its potential as a dual-action biocontrol agent.

生物防治剂（BCAs）是现代农业中替代合成化学农药的可持续、环境友好型方案。其中，链霉菌属（Streptomyces）物种因通过多样功能性状抑制植物病原菌并促进植物生长而广受认可。本研究针对命名为LZZY-S40（=CGMCC No.30320）的链霉菌菌株，采用双培养测定法评估其抗真菌活性，并通过幼苗生长试验与功能性状分析探究其植物促生（PGP）潜力。进一步通过基因组挖掘及基于液相色谱-质谱（LC-MS）的代谢组学分析，对该菌株的生物合成潜力与次生代谢物组成展开研究。菌株LZZY-S40对9种植物病原真菌均表现出广谱抗真菌活性，抑制率介于55.8%至92.8%之间，其中对玉米大斑病菌（Exserohilum turcicum）的抑制效果最强，抑制率达92.8%。后续分析显示，LZZY-S40可分泌胞外蛋白酶，这可能是其抗真菌活性的潜在作用机制之一。基因组挖掘鉴定出多个与抗菌化合物生物合成相关的次生代谢物生物合成基因簇（BGCs），包括负责十一烷基灵菌红素与灭旋霉素A生物合成的基因簇，该基因组预测结果经LC-MS分析得到验证。除抗真菌特性外，LZZY-S40可显著促进小麦幼苗生长。当浓度为10⁵ CFU·mL⁻¹时，该菌株可使幼苗根长增加88.3%、苗高增加37.9%、鲜重增加32.1%。与上述表型效应一致的是，该菌株在多项经典植物促生性状检测中呈阳性，包括吲哚-3-乙酸（IAA）合成、铁载体分泌、1-氨基环丙烷-1-羧酸（ACC）脱氨酶活性及固氮酶介导的固氮作用，为其促生能力提供了机制层面的佐证。综上，本研究结果表明，菌株LZZY-S40对多种植物病原真菌具有强效抗真菌活性，且可显著促进植物生长。本研究通过机制探究初步阐明了该菌株的抗真菌与植物促生性状相关机制，有助于深化对其作为双重功能生物防治剂应用潜力的认知。