Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 12, 2010
Publication Date: September 1, 2010
Citation: Hajeri, S., Ramadugu, C., Keremane, M.L., Vidalakis, G., Lee, R.F. 2010. Nucleotide sequence and genome organization of Dweet mottle virus and its relationship to members of the family Betaflexiviridae. Archives of Virology. 155(9):1523–1527. Interpretive Summary: Dweet mottle virus (DMV) was reported from Riverside, California in 1968 during reindexing of a ‘Cleopatra’ mandarin variety introduced from Florida in the Citrus Variety Improvement Program, the fore-runner of the present Citrus Clonal Protection Program (CCPP). DMV produced leaf mottling symptoms only in ‘Dweet’ tangor that resembling but distinct from the symptoms of psorosis and concave gum. A partial sequence analysis showed that DMV has very high sequence homology (over 96%) with the Citrus leaf blotch virus (CLBV). CLBV was first reported in Spain in an introduction of ‘Nagami’ kumquat from Corsica. Both DMV and CLBV induce mottling in ‘Dweet’ tangor and stem pitting in ‘Etrog’ citron however, only CLBV causes vein clearing in ‘Pineapple’ sweet orange and bud union crease on trifoliate and trifoliate hybrids rootstocks and has been reported to be seed transmitted. Experiments with CLBV infectious clones suggested that the bud union crease and vein clearing symptoms may be caused by a different agent associated with ‘Nagami’ kumquat sources. Since DMV and CLBV have distinct biological similarities and differences, a direct comparison of the full DMV genome at the genetic level was undertaken. The full genomic sequence and genome organization of DMV is presented here and compared to the members of Alpha- and Beta-flexiviridae family.
Technical Abstract: The nucleotide sequence of Dweet mottle virus (DMV) was determined and compared to sequences of members of the family Alpha- and Beta-flexiviridae. The DMV genome has 8747 nucleotides (nt) excluding the poly-(A) tail at the 3’ end of the genome. The overall G+C content of DMV genomic RNA is 40%. DMV genomic RNA contains three putative open reading frames (ORFs) and untranslated regions (UTR) of 73 nt at the 5’ and 541 at 3’ termini. ORF1 potentially encoding a 227.48 kDa polyprotein, which has methyltransferase, oxygenase (Alk-B), endo-peptidase, helicase, and RNA-dependent RNA polymerase (RdRP) domains. ORF2 encodes a movement protein of 40.25 kDa while ORF3 is the coat protein (CP) of 40.69 kDa polypeptide. Protein database searches showed 98-99% matches of DMV ORFs with CLBV sequences. Phylogenetic analysis, based on RdRP core domain revealed that DMV is closely related to CLBV as a member of the genus Citrivirus. DMV did not satisfy the molecular criteria for demarcation of an independent species within the genus Citrivirus under family Betaflexiviridae however; additional information for the biological properties of the virus is needed before we can definitely conclude if DMV is just a CLBV isolate.