Distinct Geminivirus Research Articles

Geminiviruses Associated with Diseased Tomatoes in Cuba

AbstractTomato plants displaying symptoms of yellowing and leaf curling were analysed for the presence of geminiviruses. Two distinct geminiviruses were present in the plants studied. One had a genome size and coat protein gene sequence similar to the Israeli strain of tomato yellow leaf curl virus (TYLCV), while the other had a smaller genome size than TYLCV that could not be amplified using primers specific for Israeli TYLCV. The presence of the Israeli strain of TYLCV has been reported in other Caribbean islands, but not in Southern Florida (USA) which is close to those islands where TYLCV has been detected. This suggests that the introduction of the Israeli strain of TYLCV to the Caribbean area may have occurred within recent times.

Pseudorecombination between infectious cloned DNA components of tomato mottle and bean dwarf mosaic geminiviruses

A newly described whitefly-transmitted geminivirus infecting tomato plants in Florida induces yellow mottling symptoms on leaves, and stunted and distorted growth. The DNA-A and DNA-B components were cloned from extracts of field-infected tomato tissue; excised monomers or uncut tandem dimers of these clones were infectious when co-inoculated on to Nicotiana benthamiana by rub-inoculation. Tomato plants inoculated directly with the DNA-A and DNA-B dimers, or indirectly by sap or graft transmission from N. benthamiana plants previously infected with the dimers, developed symptoms similar to those observed in field-infected plants. This tomato geminivirus is different from previously characterized geminiviruses, and has been named tomato mottle geminivirus (ToMoV). DNA sequence comparisons revealed that ToMoV is closely related to bean dwarf mosaic geminivirus (BDMV) and abutilon mosaic geminivirus. Infectious pseudorecombinants were made by exchanging the cloned infectious DNA components of ToMoV and BDMV and inoculating N. benthamiana plants. The presence of the inoculated DNA components in systemically infected plants was confirmed by characterization of DNA-A and DNA-B fragments amplified by the polymerase chain reaction. This is the first report of pseudorecombination between two distinct geminiviruses. The implications of this finding in geminivirus evolution are discussed.

Characterization of the Sugarcane Streak Agent as a Distinct Geminivirus

The relationship between maize streak virus and the geminivirus causing streak in sugarcane was investigated. The DNA of sugarcane streak virus does not cross-hybridize detectably with that of maize streak virus and vice versa. Restriction mapping of native replicative form viral DNA (genome size 2.7 kb) and of cloned viral DNA, combined with limited sequencing and estimated DNA sequence divergence, showed that sugarcane streak virus is as unrelated to maize streak virus and digitaria streak virus as these are different from each other. The virus is only distantly related to wheat dwarf virus and chloris striate mosaic virus. Based on these results, we propose that the agent causing sugarcane streak is a distinct geminivirus.