Mapping of the polycistronic RNAs of tomato leaf curl geminivirus

Four major transcripts from infected tomato were identified and mapped onto the monopartite genome of the geminivirus tomato leaf curl virus (TLCV). The C1, C2, and C3 ORFs are spanned by one transcript and a second internal RNA covered C2 and C3. Both these RNAs have their counterparts in the DNA A components of the bipartite subgroup of geminiviruses. The 5' ends of the virion-sense RNAs map either side of the first in-frame AUG of the V1 ORF. The 3' ends of the virion-sense RNAs are coterminal and overlap with the 3' ends of the complementary-sense RNAs. All of the RNAs have transcription regulatory sequences close to their mapped termini and the presence of overlapping transcripts suggests that temporal regulation of their synthesis may occur. The translation of these polycistronic RNAs is discussed in the light of the RNA mapping data.