Justin E. Rigden

Nucleotide sequence and genome organization of tomato leaf curl geminivirus.

The genome of tomato leaf curl virus (TLCV) from Australia was cloned and its complete nucleotide sequence determined. It is a single circular ssDNA of 2766 nucleotides containing the consensus nonanucleotide sequence present in all geminiviruses. It has six open reading frames with an organization resembling that of certain other dicotyledonous plant-infecting monopartite geminiviruses, i.e. tomato yellow leaf curl and beet curly top viruses. The regulatory sequences present indicate a bidirectional mode of transcription. A dimeric TLCV DNA clone was constructed in a binary vector and used to agroinoculate three different host species. Typical virus infections were produced, confirming that the single DNA component is sufficient for infectivity.

Analysis of sequence variation in grapevine yellow speckle viroid 1 reveals two distinct alternative structures for the pathogenic domain.

The nucleotide sequences of 24 full-length cDNA clones prepared from a field isolate of grapevine yellow speckle viroid 1 (GYSV 1) have been determined and compared with that of the previously published GYSV 1 sequence. A large number of sequence variations were observed, the majority of which occurred in the pathogenicity domain (P domain) of the viroid. The GYSV 1 variants could be divided into two types each containing a distinct secondary structure within the P domain. Monomeric exact-length RNA transcripts produced from individual clones belonging to both types were infectious in viroid-free grapevines and produced homogenous populations of progeny viroid in vivo.