Striking similarities between the nucleotide sequence and genome organization of citrus tatter leaf and apple stem...

The sequence of the 3'-terminal 2956 nucleotides, excluding the poly(A) tail, of the citrus tatter leaf virus (CTLV) genome was determined and compared with that of the apple stem grooving virus (ASGV) genome. The sequence of the 3'-terminal region of CTLV contains two overlapping open reading frames (ORFs) and a 3'-terminal non-coding region of 142 nucleotides. The long, incomplete ORF1 ends at UAG (position 2812) and encodes a protein with at least 938 amino acids (M(r) > 108,703). This protein contains the GDD motif associated with the RNA polymerase. ORF2, in a different frame within ORF1, starts at AUG (position 1248) and stops at UGA (position 2208) encoding a protein with an M(r) of 36,179 (36K). Partial homologies were found among the 36K protein of CTLV, the 50K protein of apple chlorotic leaf spot closterovirus, the 40K protein of potato virus T and the gene 1 products of caulimoviruses. The arrangement of ORFs in the 3'-terminal region of the CTLV genome is in perfect agreement with that of the ASGV genome. The sequence of the 3'-terminal 2956 nucleotides, excluding the poly(A) tail, of the CTLV genome shows 86.1% identity to that of the ASGV genome. Similarities of amino acid sequences encoded by ORF1 and ORF2 of CTLV with the corresponding regions of ASGV are 86.1% and 97.3%, respectively. These results indicate that CTLV is a capillovirus closely related to ASGV.