DNA transposon expansion drives genome plasticity in Diutina catenulata

Diutina catenulata is an ascomycetous yeast of environmental and emerging clinical relevance. Genome analysis of strains representing the major phylogenetic lineages of the species revealed a strong genetic structure, with deeply diverged clades displaying limited gene flow, likely reflecting clonal propagation or long-term historical divergence. A notable feature of D. catenulata genomes is an extensive degree of chromosomal instability associated with two DNA transposons, Dici1 and Dici2, present across all lineages, with up to 96 Dici1 copies in the type strain CBS 565^T. We experimentally demonstrate that both elements remain active and mobilize under laboratory conditions. High sequence conservation among Dici copies supports a recent and ongoing transpositional burst reshaping genome architecture. Related elements identified in multiple fungal species define a previously undescribed family of DNA transposons related to the IS630-Tc1-mariner superfamily. These findings provide a framework for studying DNA transposon proliferation and genome evolution in yeasts.