Figure 1 (Top) Negative contrast electron micrograph of virions of Citrus tristeza virus (CTV) a representative of the genus Closterovirus. Particles of members of the genus Crinivirus have the same morphology. The bar represents 100 nm. (Courtesy of R.G. Milne.). (Bottom) Beet yellows virus (BYV) particle showing a decorated extremity (arrowheads) following exposure to an antiserum to the N-terminal peptide of the coat protein analogue gene. The bar represents 100 nm. (Courtesy of D.E. Lesemann.)
Figure 2 Genome organization of Beet yellows virus, (BYV), showing the relative position of the ORFs and their expression products. P-Pro, papain-like protease; Mt, methyltransferase; Hel, helicase; Pol, RNA polymerase; HSP70, heat shock-related protein; CP, coat protein; CPd, coat protein analogue. The five boxes with the same shadowing represent the five gene block conserved among closteroviruses.
Figure 3 Map and expression strategy of Citrus trizteza virus, (CTV) genome. Narrow boxes represent putative protein products corresponding to the respective ORFs. The arrow designates the putative ribosomal frameshift. Solid lines define the two genomic regions expressed through proteolytic processing of the polyprotein precursor(s) and through the formation of a nested set of 3 co-terminal sgRNAs (from Karasev and Hilf, 1997).
Figure 4 Genome organization of Lettuce infectious yellows virus (LIYV) showing the relative position of the ORFs and their expression products. P-Pro, papain-like protease; MT, methyltranferase; HEL, helicase; POL, RNA polymerase; HSP70, heat shock-related protein; CP, coat protein; CPd, coat protein analogue.
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