Complete nucleotide sequence of the infectious cloned DNA components of tomato golden mosaic virus: potential coding regions and regulatory sequences

Abstract

The nucleotide sequences of the infectious cloned DNA com-ponents of tomato golden mosaic virus (TGMV) have been determined. DNA A (2588 nucleotides) and DNA B (2508 nucleotides) have little sequence homology except for a region of --200 bases which is almost identical in the two molecules. Analysis of open reading frames revealed six potential coding regions for proteins of mol. wt. >10 000, four in DNA A and two in DNA B. Possible regulatory signals are identified and a model for bidirectional transcription of the two genome components is presented. Comparison of the nucleotide se-quences of the DNAs of TGMV and cassava latent virus (CLV) revealed a fairly close relationship between TGMV DNA A and CLV DNA 1 and a comparatively distant rela-tionship between TGMV DNA B and CLV DNA 2. All the potential coding regions in the TGMV DNAs had counter-parts in the CLV DNAs suggesting an overall similarity in genome organisation, but six potential coding regions in the CLV DNAs had no counterparts in the TGMV DNAs. The 200-base region common to the two DNAs of each virus had little sequence homology, except for a highly conserved 33-base sequence potentially capable of forming a stable hair-pin structure. Key words: geminivirus/genome organisation/nucleotide se-quence/sequence homology/tomato golden mosaic virus Introduction Tomato golden mosaic virus (TGMV) belongs to the gemini-virus group, members of which are characterised by their twin isometric (geminate) virions, major capsid polypeptides of mol. wt. -28 000 and genomes of circular single-stranded (ss) DNA (Hamilton et al., 1981; Matthews, 1982). The genomes of TGMV and two other geminiviruses, cassava la-tent virus (CLV) (synonym African cassava mosaic virus, Bock and Woods, 1983) and bean golden mosaic virus (BGMV) consist of two ssDNA components and those of CLV have been sequenced (Hamilton et al., 1982; Bisaro et al., 1982; Stanley and Gay, 1983; Haber et al., 1981, 1983). Cloned double-stranded (ds) DNA of TGMV (Hamilton et al., 1983) and CLV (Stanley, 1983) have been shown to be in-fectious in plants giving rise to infectious progeny particles