Complete nucleotide sequence and genome organization of hibiscus chloroticringspot virus, a new member of the genus Carmovirus: Evidence for the presence and expression of two novel open reading frames

The complete nucleotide sequence of hibiscus chlorotic ringspot virus (HCRS V) was determined. The genomic RNA (gRNA) is 3,911 nucleotides long and has the potential to encode seven viral proteins in the order of 28 (p28), 23 (p23), 81 (p81), 8 (p8), 9 (p9), 38 (p38), and 25 (p25) kDa, Excluding two unique open reading frames (ORFs) encoding p23 and p25, the ORFs encode pro teins with high amino acid similarity to those of carmoviruses, In addition to gRNA, two 3'-coterminated subgenomic RNA (sgRNA) species were identifie d. Full-length cDNA clones derived from gRNA and sgRNA were constructed und er the control of a T7 promoter. Both capped and uncapped transcripts deriv ed from the full-length genomic cDNA clone were infectious. In vitro transl ation and mutagenesis assays confirmed that all the predicted ORFs except t he ORF encoding p8 are translatable, and the two novel ORFs (those encoding p23 and p25) may be functionally indispensable for the viral infection cyc le. Based on virion morphology and genome organization, we propose that HCR SV be classified as a new member of the genus Carmovirus in family Tombusvi ridae.