Abstract
The transfer of genetic information between unrelated species is referred to as horizontal gene transfer. Previous studies have demonstrated that both retroviral and non-retroviral sequences have been integrated into eukaryotic genomes. Recently, we identified many non-retroviral sequences in plant genomes. In this study, we investigated the evolutionary origin and gene transfer of domains present in endornaviruses which are double-stranded RNA viruses. Using the available sequences for endornaviruses, we found that Bell pepper endornavirus-like sequences homologous to the glycosyltransferase 28 domain are present in plants, fungi, and bacteria. The phylogenetic analysis revealed the glycosyltransferase 28 domain of Bell pepper endornavirus may have originated from bacteria. In addition, two domains of Oryza sativa endornavirus, a glycosyltransferase sugar-binding domain and a capsular polysaccharide synthesis protein, also exhibited high similarity to those of bacteria. We found evidence that at least four independent horizontal gene transfer events for the glycosyltransferase 28 domain have occurred among plants, fungi, and bacteria. The glycosyltransferase sugar-binding domains of two proteobacteria may have been horizontally transferred to the genome of Thalassiosira pseudonana. Our study is the first to show that three glycome-related viral genes in the genus Endornavirus have been acquired from marine bacteria by horizontal gene transfer.
Highlights
Eukaryotic genomes have acquired genetic information through two different mechanisms throughout the course of evolution
We propose a hypothesis related to the evolutionary origins and horizontal gene transfer of endornaviral genes
To detect predicted conserved domains in each endornavirus, the full-length amino acid sequences were subjected to analysis with the SMART program, and sequence data associated with known domains were retrieved from the Pfam database
Summary
Eukaryotic genomes have acquired genetic information through two different mechanisms throughout the course of evolution. A total of 30 nonredundant endogenous BPEV-like sequences, referred to as EBPEs, were identified in 19 plant species (Table 1). Only T. pseudonana contains an EBPE, and other monocot plants, such as sorghum and rice, carry several EBPEs. Interestingly, all identified EBPEs are homologous to one specific domain of BPEV, which is referred as glycosyltransferase 28 (GT28) domain (Figure 1A).
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