Nadeem A1, Weng Z, Nelson MR, Xiong Z
Department of Plant Pathology, Forbes 204, University of Arizona, Tucson, AZ 85721, USA.
1Current address: Central Cotton Research Institute, Old Shujahabad Road, Multan, Pakistan.
Z. Xiong, Department of Plant Pathology, Forbes 204, University of Arizona, Tucson, AZ
Telephone: 520-621-9869 Fax 520-621-9290 email: firstname.lastname@example.org
Cotton leaf crumple virus (CLCrV) and cotton leaf curl virus (CLCuV) are two whitefly-transmitted geminiviruses that infect cotton. Using a polymerase chain reaction (PCR)-based technique, the complete DNA A component of each virus was amplified as two DNA fragments from total nucleic acids extracted from infected cotton leaves and subsequently cloned. Two pairs of PCR primers were designed according to conserved regions of several published, whitefly-transmitted geminivirus sequences. Electrophoretic analysis of the PCR products indicated that the DNA A of CLCrV and CLCuV was approximately 2.6 kb and 2.7 kb, respectively. Southern hybridization analyses of the cloned PCR fragments showed that CLCrV DNA and CLCuV DNA did not hybridize with each other under high stringency conditions whereas they hybridized weakly with each other under low stringency conditions. Riboprobes prepared from cloned DNA fragments also hybridized with their respective single-stranded virion DNA and the double-stranded replicative form extracted from infected cotton leaves. A smaller-than-genomic viral DNA, presumably a subgenomic DNA, was detected in CLCuV-infected cotton, but not in CLCrV-infected cotton by the hybridization. The hybridization data are consistent with partial sequence analysis of the AC1 gene and the capsid protein gene. Although both viruses share a high degree of nucleic acid identity, CLCrV is more closely related to the New World geminiviruses such as Abutilon mosaic virus, sida golden mosiac virus, bean dwarf mosaic virus, and tomato mottle virus; whereas CLCuV is more closely related to the Old World viruses such as ageratum yellow vein virus, tomato leaf curl virus, African cassava mosaic virus, and tomato yellow leaf curl virus. Our data indicate that CLCrV and CLCuV are two distinct and distantly related geminiviruses.