Identification of a novel DNA molecule associated with Tobacco leaf curl virus

A circular DNA molecule, designated as DNAbeta, was identified in tobacco plants infected with,Tobacco leaf curl virus (TLCV) isolates Y5 and Y8 by PCR using primers based on the conserved region of the two reported DNAbeta sequences of whitefly-transmitted geminiviruses (WTGs). The complete nucleotide sequences of DNAbeta of Y5 and Y8 (TLCV DNAbeta) were determined. Y5 DNAbeta comprises 1333 nucleotides encoding 8 predicted ORFs with 4 ORFs in virion-sense DNA and 4 ORFs in complementary-sense DNA; Y8 DNAbeta consists of 1338 nucleotides encoding 7 predicted ORFs with 4 ORFs in virion-sense DNA and 3 ORFs in complementary-sense DNA. TLCV DNAbeta has little sequence homology to DNA-A of TLCV, except that it shares conserved TAATATTAC loop sequence with TLCV DNA-A. Sequence comparison showed that Y5 DNAbeta shared 85% sequence homology with Y8 DNAbeta, and both Y5 DNAbeta and Y8 DNAbeta had relatively low sequence identity (51%-65%) with the reported DNAbeta molecules associated with Ageratum yellow vein virus and Cotton leaf curl virus. The immunotrapping PCR and whitefly transmission tests showed that DNAbeta molecule could be encapsidated in virus particle and transmitted by Bemisia tabaci. This is the first report of DNAbeta associated with WTGs in China.