Cysteine-rich repeats identified as markers of horizontal gene transfer in eukaryotes
Researchers have identified a class of cysteine-rich protein repeats (CysRReps) associated with horizontal gene transfer (HGT) events across 43 protein families and hundreds of eukaryotic species. Starting from a single fungal protein in Neocallimastix californica, a BLASTp search uncovered 859 eukaryotic proteins sharing strong similarity to bacterial, archaeal, or viral counterparts. The findings suggest CysRReps may be markers — or even facilitators — of a universal molecular mechanism enabling gene transfer across the tree of life.
Horizontal gene transfer (HGT), the movement of genetic material between non-parental organisms, is well established in prokaryotes but has been underappreciated as a driver of evolutionary novelty in eukaryotes. In this preprint study, researchers began with a cysteine-rich repeat-containing protein from the chytridiomycete fungus Neocallimastix californica and used sequence similarity searches to identify 859 additional eukaryotic proteins across 43 protein families, each with close matches to bacterial, archaeal, or viral sequences. The prokaryotic counterparts span bacteria from 15 distinct phyla representing highly diverse physiologies and habitats, while viral diversity is largely concentrated in the class Caudoviricetes — a group of tailed bacteriophages — pointing toward a possible virus-mediated DNA integration mechanism. The HGT-derived proteins were found across multiple eukaryotic taxa, including organisms already recognized as frequent recipients of horizontal gene transfers. While the precise biological function of CysRReps themselves remains unknown, their consistent association with cross-domain transfer events across such a broad phylogenetic range implies they may play a structural or functional role in the transfer process. The authors propose that CysRReps could serve as a targeted molecular signature for detecting and studying HGT events, potentially accelerating progress in a field currently limited by the lack of systematic detection tools.
What's missing
As a preprint posted on bioRxiv, this study has not yet undergone peer review, and its conclusions should be treated as preliminary. The function of CysRReps remains entirely uncharacterized, meaning the proposed mechanistic role in facilitating gene transfer is speculative. The study relies on sequence similarity (BLASTp) as its primary evidence for HGT, which can produce false positives due to convergent evolution or database contamination; phylogenetic analyses confirming directionality of transfer are not described in the abstract. The relative contribution of virus-mediated versus other HGT mechanisms is inferred from taxonomic patterns rather than experimental validation.
What different sources said
- bioRxivCenter
Cysteine-rich repeats trace past horizontal gene transfers in eukaryotes
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