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Abstract:
Arthrobotrys oligospora, a nematode-trapping fungus, exhibits a dual lifestyle as both a saprophyte and predator, showcasing remarkable versatility in adapting to diverse environmental conditions and nutrient availabilities. In its carnivorous mode, it traps, kills, and consumes nematodes, ensuring its success even in nutrient-deficient environments. However, the number of traps and their efficacy varies widely among A. oligospora isolates, even when exposed to similar environmental conditions and nematode cues. To gain deeper insights into the population dynamics of this nematode-trapping fungus, we collected and sequenced over 180 A. oligospora wild isolates from various locations across Taiwan. We assembled pangenomes for each isolate, revealing substantial variation in genome size and gene count—some differing by up to 3 Mb and lacking up to 1000 genes compared to the reference genome. Variations also extend to the number and distribution of transposable elements within our population. Identification of orthologs among isolates and related species allowed us to categorize genes unique to A. oligospora and pinpoint potential candidates involved in the trapping process. Our investigation into population structure and phylogeny of A. oligosporawild isolates revealed eight distinct subpopulations, hinting at possible interbreeding among them. We computed trapping phenotype for selected subpopulations, aiming to discern genes and g enomic features associated with trapping ability. Our genome-wide association study (GWAS) identified mutations in genes correlated with the ability to form traps across isolates, unveiling novel candidate genes potentially linked to the still elusive trapping process of nematode-trapping fungi. This research constitutes the most comprehensive study to date of a natural population of nematode-trapping fungi. We believe that our findings will contribute to a better understanding of the genetic mechanisms governing the trapping process and the population dynamics of nematode-trapping fungi.
