Beauveria bassiana acts as a beneficial endophyte in tea crops, modulating microbial communities and metabolic pathways to enhance plant growth

Entomopathogenic fungi have the ability to both directly kill insect pests and act as plant endophytic fungi to impact plant growth and development. Despite this, the widespread endophytic use of these fungi in tea plants (Camellia sinensis) is still limited. This study examined how Beauveria bassiana colonizes tea plant tissues and its impact on tea plant growth and development. Through amplicon sequencing and liquid chromatography-tandem mass spectrometry (LC-MS/MS), the study investigated the response patterns of dominant endophytic microbial populations in tea plants during fungal colonization and the alterations in secondary metabolites in tea plants due to the colonization process. B. bassiana effectively colonized tea seedlings through root irrigation and foliar spraying methods, showing a preference for stems, and the colonization persisted for more than 90 days. Colonization resulted in a reduction in the diversity and structural stability of the endophytic microbial community in tea plants; however, it also enhanced the importance of ecologically mutualistic relationships or cooperative interactions in community assembly. Additionally, colonization had a more pronounced effect on endophytic fungi compared to endophytic bacteria. It led to an increase in the relative abundance of arbuscular mycorrhizal fungi in root tissues and a decrease in the relative abundance of total plant pathogens in tea plant tissues. Terpenoids were the most significantly associated differential metabolites following B. bassiana colonization, followed by steroids and their derivatives, and flavonoids. Colonization by B. bassiana resulted in elevated levels of the majority of differential metabolites in tea plant stems at the onset of colonization. The colonization of B. bassiana in tea plants displayed a strong positive correlation with 26 distinct metabolites, such as proanthocyanidin B2 and L-malic acid. This colonization altered the endophytic microbial community, impacting metabolic pathways associated with plant hormone synthesis, volatile compound production, as well as the growth, development, and defense of tea plants.

虫生真菌（Entomopathogenic fungi）兼具直接杀灭昆虫害虫的能力，同时可作为植物内生真菌（plant endophytic fungi）影响植物的生长发育。尽管具备上述特性，但这类真菌在茶树（Camellia sinensis）中的内生应用仍存在较大局限。本研究探究了球孢白僵菌（Beauveria bassiana）在茶树组织中的定殖特征，及其对茶树生长发育的影响。本研究通过扩增子测序（amplicon sequencing）与液相色谱-串联质谱（LC-MS/MS）技术，解析了茶树内生优势微生物种群在真菌定殖过程中的响应模式，以及定殖引发的茶树次生代谢物变化。球孢白僵菌可通过根灌与叶面喷施两种方式有效定殖茶苗，且对茎部具有显著的定殖偏好性，定殖状态可维持90天以上。定殖过程会降低茶树内生微生物群落的多样性与结构稳定性，但同时强化了生态共生关系或协同互作在群落构建中的核心作用。此外，相较于内生细菌，球孢白僵菌定殖对内生真菌的调控效应更为显著：其可提升根系组织中丛枝菌根真菌（arbuscular mycorrhizal fungi）的相对丰度，并降低茶树组织内总植物病原菌的相对丰度。萜类化合物（terpenoids）是球孢白僵菌定殖后差异丰度最显著的代谢物类别，其次为类固醇及其衍生物（steroids and their derivatives）与黄酮类化合物（flavonoids）。在定殖初期，球孢白僵菌定殖会使茶树茎部内多数差异代谢物的含量显著升高。球孢白僵菌在茶树中的定殖情况，与26种特定代谢物（如原花青素B2（proanthocyanidin B2）与L-苹果酸（L-malic acid））呈显著正相关。该定殖过程通过改变茶树内生微生物群落，进而调控了植物激素合成、挥发性化合物生成相关代谢通路，并最终影响茶树的生长发育与防御机制。