Algae-to-host horizontal gene transfer in Paramecium bursaria is associated with host adaptation during endosymbiosis.

Lei Yang; Deyu Wei; Yuan Li; Xiao Chen

doi:10.1016/j.ympev.2026.108726

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Algae-to-host horizontal gene transfer in Paramecium bursaria is associated with host adaptation during endosymbiosis.

Lei Yang·Deyu Wei·Yuan Li·Xiao Chen

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Abstract

Paramecium bursaria maintains a stable endosymbiosis with green algae, yet the evolutionary consequences of this association remain unclear. Here, we screened the host genome for algal-derived horizontally transferred genes (HTGs) using a lineage-aware workflow designed to detect horizontal gene transfer (HGT) between two defined lineages. We identified 16 candidate HTGs, including four putative newly transferred genes and 12 homologous transferred genes, most of which were functionally associated with redox homeostasis and metabolism. Five HTGs showed symbiosis-dependent expression. RNAi knockdown of GH32s and SATs reduced host proliferation, total cell area, and motility, while GH32s knockdown also reduced endosymbiont load. Duplication patterns suggest that most transfers may have occurred after the P. bursaria lineage diverged from the sampled Paramecium species but before its lineage-specific whole-genome duplication (WGD). The HTGs also showed host-associated shifts in GC content and gene length, while representative HTGs retained conserved domains and functional motifs. Together, our results support algae-to-host HGT in P. bursaria and suggest that some transferred genes may contribute to metabolic integration during endosymbiosis.

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Gene Transfer, Horizontal Symbiosis Paramecium Phylogeny Chlorophyta Evolution, Molecular RNA Interference Ciliate Endosymbiosis Green algae Horizontal gene transfer Journal Article

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Lei Yang, Deyu Wei, Yuan Li, Xiao Chen. 2026-08-31. Algae-to-host horizontal gene transfer in Paramecium bursaria is associated with host adaptation during endosymbiosis.. https://doi.org/10.1016/j.ympev.2026.108726

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Journal Article resource Chlorophyta subject Ciliate subject Endosymbiosis subject Evolution, Molecular subject Gene Transfer, Horizontal subject Green algae subject Horizontal gene transfer subject Journal Article subject Paramecium subject

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