# FoTeRs: a novel family of telomere-associated retrotransposons in Fusarium oxysporum

## TL;DR

This paper discovers a new type of jumping gene in a fungus that causes disease, which inserts itself specifically at chromosome ends and may influence genome stability.

## Contribution

The study identifies FoTeRs, a novel retrotransposon family in Fusarium oxysporum, with unique telomere-targeting integration and dual evolutionary dynamics.

## Key findings

- FoTeRs are non-LTR retrotransposons localized exclusively at chromosome ends in Fusarium oxysporum.
- Functional FoTeR elements are under purifying selection, while others show mutational decay due to RIP mutations.
- FoTeRs co-localize with telomere-linked helicases, suggesting a role in telomere maintenance.

## Abstract

Transposable elements (TEs) are dynamic components of eukaryotic genomes, playing a crucial role in genome evolution and plasticity, particularly in unstable regions such as chromosome ends. In the globally significant fungal pathogen Fusarium oxysporum, we identified and characterized a novel family of non-LTR retrotransposons named FoTeRs (F. oxysporum Telomeric Retrotransposons). These elements are consistently and uniquely localized at chromosome ends, representing a rare example of site-specific TE integration. Phylogenetic analysis confirmed that FoTeRs form a distinct clade with other telomere-targeting retrotransposons, suggesting a shared evolutionary history and a convergent mechanism for telomeric integration. We found that individual FoTeR elements exhibit a duality in their evolutionary status. Putatively functional elements are under strong purifying selection, indicating that their protein-coding regions are highly conserved. This contrasts with the presence of other, non-functional copies that exhibit signs of mutational decay, a process accelerated by Repeat-Induced Point (RIP) mutations —a fungal-specific defense mechanism. The high density of upstream variable number tandem repeats (VNTRs) also contributes to their genomic plasticity. Furthermore, FoTeRs frequently co-localize with host Telomere-Linked Helicases (TLHs), suggesting a potential functional link in telomere maintenance. This study provides crucial insights into the role of TEs in shaping the genome architecture and adaptive potential of this important fungal pathogen.

The online version contains supplementary material available at 10.1186/s13100-025-00385-6.