Differential transcriptional activity of plant-pathogenic begomoviruses in their whitefly vector (Bemisia tabaci, Gennadius: Hemiptera Aleyrodidae)

Plant-pathogenic begomoviruses have a complex association with their whitefly vector and aspects concerning virus genetic activity (genome replication and gene transcription) within the insect remain highly controversial. Virus transcript abundance was assessed by quantifying selected gene transcripts of Tomato mottle virus (ToMoV, a New World bipartite begomovirus) and Tomato yellow leaf curl virus (TYLCV, an Old World monopartite begomovirus) in whiteflies (Bemisia tabaci biotype B) after feeding on virus-infected tomato plants and after subsequent transfer to cotton, a plant that is immune to the selected begomoviruses. Real-time RT-PCR was performed using specific primers for three ToMoV genes (AV1, BC1 and BV1) and three TYLCV genes (V1, V2 and C3). The ToMoV gene transcripts rapidly became undetectable in whiteflies following transfer from tomato to cotton, probably because degradation was not accompanied by new synthesis. On the other hand, TYLCV transcripts increased after transfer of whiteflies to cotton, indicating active TYLCV transcription. Interestingly, the difference observed in ToMoV and TYLCV transcripts in the vector parallel observations on the different biological effects of these viruses on whiteflies, i.e. TYLCV, but not ToMoV, reduces whitefly fitness.