Genomic comparisons of the laurel wilt pathogen, Raffaelea lauricola, and related tree pathogens highlight an arsenal of pathogenicity related genes.

ABSTRACT

Raffaelea lauricola is an invasive fungal pathogen and symbiont of the redbay ambrosia beetle (Xyleborus glabratus) that has caused widespread mortality to redbay (Persea borbonia) and other Lauraceae species in the southeastern USA. We compare two genomes of R. lauricola (C2646 and RL570) to seven other related Ophiostomatales species including R. aguacate (nonpathogenic close relative of R. lauricola), R. quercus-mongolicae (associated with mortality of oaks in Korea), R. quercivora (associated with mortality of oaks in Japan), Grosmannia clavigera (cause of blue stain in conifers), Ophiostoma novo-ulmi (extremely virulent causal agent of Dutch elm disease), O. ulmi (moderately virulent pathogen that cause of Dutch elm disease), and O. piceae (blue-stain saprophyte of conifer logs and lumber). Structural and functional annotations were performed to determine genes that are potentially associated with disease development. Raffaelea lauricola and R. aguacate had the largest genomes, along with the largest number of protein-coding genes, genes encoding secreted proteins, small-secreted proteins, ABC transporters, cytochrome P450 enzymes, CAZYmes, and proteases. Our results indicate that this large genome size was not related to pathogenicity but was likely lineage specific, as the other pathogens in Raffaelea (R. quercus-mongolicae and R. quercivora) had similar genome characteristics to the Ophiostoma species. A diverse repertoire of wood-decaying enzymes were identified in each of the genomes, likely used for toxin neutralization rather than wood degradation. Lastly, a larger number of species-specific, secondary metabolite, synthesis clusters were identified in R. lauricola suggesting that it is well equipped as a pathogen, which could explain its success as a pathogen of a wide range of lauraceous hosts.