# Transcriptome Analysis of the Pathogenic Mechanism of the Novel Pathogenic Fungus Bipolaris fujianensis in Chinese Fir (Cunninghamia lanceolata) Shoot Blight

## TL;DR

This study explores how the fungus Bipolaris fujianensis causes disease in Chinese fir by analyzing gene activity during infection.

## Contribution

The study identifies key genes and pathways involved in the pathogenicity of Bipolaris fujianensis, including those related to toxin production.

## Key findings

- 4133 differentially expressed genes were identified during infection of Chinese fir by Bipolaris fujianensis.
- Transporters and hydrolases were found to play essential roles in the pathogenic process.
- Cytochrome P450 and MFS transporters are likely involved in the biosynthesis and transport of the toxin ophiobolin F.

## Abstract

The molecular pathogenesis of Bipolaris fujianensis, a novel fungal pathogen causing shoot blight in Chinese fir (Cunninghamia lanceolata), remains unclear. Through comparative transcriptomics, we analyzed its gene expression during infection. Key findings include the identification of differentially expressed genes involved in transport, hydrolysis, carbon metabolism, and biosynthesis of secondary metabolites. Notably, we predicted the involvement of cytochrome P450 and a major facilitator superfamily (MFS) transporter in the production and transport of the diterpenoid toxin ophiobolin F. These insights advance the understanding of B. fujianensis virulence and may facilitate the development of control strategies against this disease.

Bipolaris fujianensis is a novel pathogenic species causing Chinese fir (Cunninghamia lanceolata) shoot blight (CFSB), first discovered in Nanping City, Fujian Province. However, its molecular pathogenic mechanisms remain largely unknown. Elucidating theses mechanisms has the potential of aiding future developments in disease management and resistance breeding in Chinese fir. In this regard, we examined the expression pattern of B. fujianensis grown on PDA (BGPDA), and during infection of Chinese fir at 24 h (BGCF-E), 48 h (BGCF-M), and 5 d (BGCF-L) post inoculation. Comparative transcriptome analysis identified 4133 differentially expressed genes (DEGs), including 1778 upregulated and 2355 downregulated in BGCF compared with BGPDA. During the infection process, Gene ontology (GO) enrichment analysis indicated that transporters and hydrolases in the molecular function categories play essential roles. Kyoto encyclopedia of genes and genomes (KEGG) analyses showed glycolysis/gluconeogenesis, carbon metabolism, and secondary metabolite biosynthesis were the major enriched pathways. Furthermore, this pathogen could produce diterpenoid toxin ophiobolin F, with cytochrome P450 and MFS transport proteins likely involved in its biosynthesis and transport predicted by RT-qPCR.