Recombination, distribution and evolution of endogenous retroelements in birds.
Krishnan, Mallika
2003
Abstract
Endogenous retroviruses have been observed in almost all vertebrates. Most work on avian retroviruses has focused on alpharetroviruses in domesticated galliform species. Very little is known about avian retroviral diversity, evolution and distribution outside of domesticated birds. To understand retroviral origins, life histories and mechanisms of transmission, a greater knowledge of the diversity and distribution of retroviruses in non-domesticated species is required. Comparisons of well-corroborated retroviral and host species phylogeny for phylogenetic congruence or incongruence can aid in estimating the relative frequency of vertical transmission compared to horizontal transmission of retroviruses among host species. Six novel replication defective retroelements were isolated from a <italic> Colinus virginianus</italic> (Northern Bobwhite quail) and a <italic>Dendragapus falcipennis</italic> (Siberian Grouse) individual. Two of the retroelements have regions with similarity to Murine Endogenous Retrovirus-L like polymerase (<italic>pol</italic>). Distribution of <italic>pol</italic> in avian hosts indicates a history of horizontal transmission. The <italic>pol</italic> element was observed in three non-galliform species, <italic>Falco peregrinus</italic> (Peregrine falcon), <italic>Accipiter cooperii </italic>(Cooper's hawk), and <italic> Melopsittacus undulata</italic> (Budgerigar). Reverse transcriptase (RT) elements were observed in association with TERV-like retroelements in one galliform and four non-galliform species. The RT is monophyletic within a TERV group of viruses. ASLV <italic>gag</italic> was also observed in the Peregrine Falcon. In a study of distribution and evolution of alpharetroviruses, avian sarcoma and leukosis virus (ASLV) <italic>gag</italic> genes were found in 26 species of galliform birds from various geographic regions. 19 of the 26 host species were not previously known to contain ASLVs. Vertical transmission of ASLVs is inferred from congruent ASLV and host phylogenies for <italic> Perdix, Gallus,</italic> and two <italic>Lagopus</italic> species. Horizontal transmission of ASLVs among some members of the Tetraoninae sub-family (grouse and ptarmigan) is supported by the ASLV phylogeny reflecting geographic distribution and proximity of hosts rather than host species phylogeny. A replication-defective retrovirus Tetraonine Endogenous Retrovirus (TERV) was isolated from <italic>Bonasa umbellus</italic> (Ruffed Grouse). TERV consists of putative Gag and Env proteins flanked by long terminal repeats. Reverse transcription-PCR analysis showed that <italic>gag</italic> sequences closely related to TERV are transcribed in the host.Subjects
Accipiter Cooperii Avian Sarcoma And Leukosis Virus Birds Bonasa Umbellus Colinus Virginianus Dendragapus Falcipennis Distribution Endogenous Evolution Falco Peregrinus Melopsittacus Undulata Recombination Retroelements
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