English
Evolution of Lichenization in Verrucariales Inferred from Phylogenomic Analysis
Chang Wan Seo1, Jung-Jae Woo2, and Seung Yoon Oh3*
1Global Institute for Advanced Nanoscience & Technology, Changwon National University, Changwon, South Korea
2Gyeongnam Bio and Anti-aging Core Facility, Changwon National University, Changwon, South Korea
3Department of AI-Integrated Biological Sciences, Changwon National University, Changwon, South Korea
*Email: syoh@changwon.ac.kr
Verrucariales (Eurotiomycetes, Ascomycota) is a predominantly lichen-forming fungal order within Chaetothyriomycetidae, yet the genomic consequences of the transition to obligate symbiosis in this lineage remain poorly understood. We retrieved publicly available genomes of Verrucariales, the sister order Chaetothyriales, the outgroup Pyrenulales, and photobiont Prasiolales. All genomes were re-annotated using a standardized pipeline to enable unbiased comparison. Phylogenomic analysis of clade-specific orthogroups revealed that Verrucariales retain substantially fewer lineage-specific gene families than Chaetothyriales, consistent with gene loss accompanying the evolution of obligate lichenization. Functional annotation integrated with genome-scale metabolic models reconstructed across Verrucariales showed that gene retention is biased toward secondary metabolite biosynthesis, desiccation tolerance, and lichen thallus development. Lineage-specific gene family expansions were additionally identified in carbohydrate-binding lectins and rhodopsins. Horizontal gene transfer between mycobiont and photobiont genomes was assessed to identify gene exchange at the symbiotic interface. These contrasting patterns of gene gain and loss suggest that the transition to obligate lichenization in Verrucariales was driven by selective gene retention for symbiosis-related functions and concurrent loss of free-living metabolic capacity.
[This work was supported by a grant from the Korea Basic Science Institute (National research Facilities and Equipment Center) (2023R1A6C101B022) and Global – Learning & Academic research institution for Master’s·PhD students, and Postdocs (LAMP) Program of the National Research Foundation of Korea (NRF) grant (No. RS-2024-00444460) funded by the Ministry of Education.]