Extensive retroviral diversity in shark.
BACKGROUND
Retroviruses infect a wide range of vertebrates. However, little is known about the diversity of retroviruses in basal vertebrates. Endogenous retrovirus (ERV) provides a valuable resource to study the ecology and evolution of retrovirus.


RESULTS
I performed a genome-scale screening for ERVs in the elephant shark (Callorhinchus milii) and identified three complete or nearly complete ERVs and many short ERV fragments. I designate these retroviral elements "C. milli ERVs" (CmiERVs). Phylogenetic analysis shows that the CmiERVs form three distinct lineages. The genome invasions by these retroviruses are estimated to take place more than 50 million years ago.


CONCLUSIONS
My results reveal the extensive retroviral diversity in the elephant shark. Diverse retroviruses appear to have been associated with cartilaginous fishes for millions of years. These findings have important implications in understanding the diversity and evolution of retroviruses.
Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Center for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu, 210023, China. guanzhu@email.arizona.edu.|Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85719, USA. guanzhu@email.arizona.edu.
Guan-Zhu
GZ
Han
D000818:Animals; D016000:Cluster Analysis; D020077:Endogenous Retroviruses / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D014644:Genetic Variation; D010802:Phylogeny; D012192:Retroviridae Infections / Q000662:veterinary* / Q000821:virology; D017385:Sequence Homology; D012754:Sharks / Q000821:virology*