Identification and comparative genomic analysis of endophytic fungi in Bletilla striata and its potential for promoting militarine bioaccumulation

Bletilla striata (Thunb.) Reichb.f is renowned for its traditional medicinal applications and a spectrum of pharmacological activities, which is intricately linked to militarine. Addressing sustainable production of B. striata and militarine necessitates innovative strategies. Endophytic fungi, residing within plant tissues and establishing symbiotic relationships, act as secondary genomes of plants, co-regulating plant growth and secondary metabolite synthesis. Despite their potential, the genetic and metabolic diversity, functional activity, and regulatory interactions of endophytic fungi with B. striata remain unexplored. This study aims to bridge this gap by investigating endophytic fungi that could enhance B. striata growth and militarine biosynthesis. The study revealed that endophytic fungi from pseudobulbs, roots, and stems were co-cultured with callus tissue of B. striata, and it was discovered that Serendipita indica from the Serendipita genus can enhance militarine accumulation. Subsequently, key genes, core enzymes, and regulatory factors related to militarine biosynthesis in the S. indica genome were analyzed. By employing advanced biotechnological and comparative genomic approaches, we elucidated the composition and distribution of regulatory factors across different endophytic fungal genomes associated with B. striata. This research not only advances our understanding of the symbiotic relationship between B. striata and its endophytic fungi but also provides a foundational blueprint for the sustainable exploitation and enhancement of militarine production.