Bemisia tabaci – Tomato Yellow Leaf Curl Virus Interaction Causing Worldwide Epidemics

Tomato yellow leaf curl virus (TYLCV) is a begomovirus that threatens tomato production worldwide. TYLCV is transmitted in a circulative manner by the whitefly Bemisia tabaci. Once ingested, TYLCV was detected in the insect midgut after 1 h, in the haemolymph after 1.5 h, and in the salivary glands after 7 h. Whiteflies were able to infect tomato plants after 8 h. TYLCV survival in the haemolymph of B. tabaci is ensured by the interaction of virus particles with a GroEL homologue produced by the whitefly endosymbionts. The relation between TYLCV and its vector are intricate. Following a short acquisition period, the virus remains associated with B. tabaci for the 4 weeks-long adult life of the insect. During this period, infectivity decreased from 100 to 10–20%. The long-term presence of TYLCV in B. tabaci was associated with a decrease in longevity and fertility. Similar results were reported with Tomato yellow leaf curl China virus (TYLCCNV). The question of whether TYLCV is expressed and replicates in its vector is not settled. Transcripts of TYLCV genes encoded by the genome strand as well as by the genome complementary strand have been detected in B. tabaci following virus acquisition. TYLCV was found to be transmitted transovarially up to the adult stage of the first progeny generation, as did Tomato yellow leaf curl Sardinia virus (TYLCSV); however contrary to TYLCV, the whiteflies were not able to transmit the disease to tomato plants. TYLCV and TYLCCN could be transmitted with various efficiency during mating. A cDNA microarray was constructed to discover the genes involved in TYLCV-B. tabaci interactions.