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

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.