Possible emergence of new geminiviruses by frequent recombination

Although exchange of genetic information by recombination plays a role in t he evolution of viruses, the extent to which it generates diversity is not clear. We analyzed genomes of geminiviruses for recombination using a new s tatistical procedure developed to detect gene conversions. Geminiviruses (f amily, Geminiviridae) are a group of plant viruses characterized by a genom e of circular single-stranded DNA (similar to 2700 nucleotides in length) e ncapsidated in twinned quasi-isometric particles. Complete nucleotide seque nces of geminiviruses were aligned, and recombination events were detected by searching pairs of viruses for sequences that are significantly more sim ilar than expected based on random distribution of polymorphic sites. The a nalyses revealed that recombination is very frequent and occurs between spe cies and within and across genera. Tests identified 420 statistically signi ficant recombinant fragments distributed across the genome. The results sug gest that recombination is a significant contributor to geminivirus evoluti on. The high rate of recombination may he contributing to the recent emerge nce of new geminivirus diseases. (C) 1999 Academic Press.