Fig. 1.

Schematic diagrams of transgene constructs used in tobacco and/or tomato transformation. (Right) The predicted structure of RNA transcripts from these transgenes. RPVSat is a full-length (322-nt) sequence of the cereal yellow dwarf virus RPV satellite. The PSTVd sequence in GUS:PSTVd[+] and GUS:PSTVd[-] contains several minor sequence mutations (arising from cloning) compared with the 359-nt wild-type PSTVd-RG1 sequence (deletions of G₁₆₈ and C₃₁₈G₃₁₉ and single-nucleotide substitutions of C₁₈₅→T and C₂₃₁→G), but these mutations do not cause significant alteration to the predicted rod-like structure of the viroid RNA. The sense PSTVd sequence in hpPSTVd starts at nucleotide 16 and ends at nucleotide 355 of the RG1 strain, with one nucleotide substitution of G₂₈₁→A, and the antisense sequence is the same as that in the GUS:PSTVd fusion constructs. There are two versions (A and B) for the hpY-Sat and d/rY-Sat constructs; the Y-SatA sequence has the size of a wild-type Y-Sat RNA (369 nt) but with two single-nucleotide substitutions of A₂₉₃→G and A₃₀₈→G, and Y-SatB has a 5-nt deletion (nucleotides 192-196), which constitutes part of the yellow symptom domain, plus four single-nucleotide substitutions of G₈₀→A, G₁₂₈→ C, G₂₀₄→T, and A₂₁₄→T. The hpGUS sequence is the same as that described in ref. 18. 35S-P, cauliflower mosaic virus 35S promoter; Ocs-T, 3′ region of Agrobacterium octopine synthase gene; i/r, inverted-repeat sequences.