Chromosome-Level Genome Assembly and Annotation of the White-Rot Fungus Pappia fissilis Provide New Insights into Its Genome Evolution, Wood-Decay Ecology, and Secondary Metabolic Potential

Pappia fissilis is a white-rot fungus capable of colonizing lignocellulosic substrates and decomposing plant cell wall components, and is likely involved in the degradation of woody debris and carbon cycling in forest ecosystems. A variety of lanostane-type triterpenoids and other bioactive compounds have been isolated from its fruiting bodies, pointing to potential value in natural product development. However, previous studies on this species have been largely confined to taxonomy, mitochondrial genomics, and chemical profiling of fruiting bodies, leaving its genomic features and the genetic underpinnings of wood decay and secondary metabolism poorly characterized. Here, we leveraged a hybrid sequencing strategy combining PacBio HiFi, Illumina, and Hi-C data to generate a chromosome-level genome assembly and annotation for P. fissilis, and conducted comprehensive phylogenomic, comparative genomic, CYP450, CAZyme, and biosynthetic gene cluster (BGC) analyses, which report the first genome resource for this species. The assembled genome spans 38.63 Mb, with 97.52% of the sequence anchored to 11 chromosomes, a BUSCO completeness of 95.4%, and 9499 predicted protein-coding genes. Phylogenomic analysis recovered P. fissilis as sister to a clade comprising Phlebia radiata and P. brevispora, with an estimated divergence time of approximately 53.17 Mya. The genome contains 153 CYP450 genes, 436 CAZyme genes, and 26 candidate BGCs harboring a total of 30 core biosynthetic genes (22 terpene, 5 T1PKS, 1 T3PKS, 2 β-lactone); these core genes are predominantly associated with terpene biosynthesis, and also encompass diverse types of polyketide synthase (PKS) genes as well as genes implicated in β-lactone biosynthesis. Collectively, these results establish a chromosome-level reference for investigating the genome evolution, wood-decay ecology, and secondary metabolic potential of P. fissilis, and lay the groundwork for future functional characterization of candidate biosynthetic genes and their associated natural products.