Mutations in the capsid protein of TYLCSV alter the ability of the virus to circulate within whiteflies.

Tomato yellow leaf curl Sardinia virus (TYLCSV) is a monopartite Begomovirus (Geminiviridae). A functional capsid protein (CP) is essential for both the infection of plants and the transmission by the whitefly vector Bemisia tabaci. The CP of the wild type (wt) virus contains two glutamines (Q129 and Q134) that are essential for infectivity and transmissibility. A double mutation Q129P and Q134H (PH mutant) completely abolishes insect transmissibility (Noris et al., 1998, J. Virol. 72:10050). To study the role of the CP in whitefly transmissibility, we have compared the acquisition and retention of the wt (QQ) and of the PH mutant viruses, both in the vector and in a non-vector whitefly, Trialeurodes vaporariorum. B. tabaci acquired the wt and the PH mutant in comparable amounts and with similar efficiencies. Both viruses were retained in the insects with the same kinetics up to 10 days. Compared to B. tabaci, the non vector T. vaporariorum acquired the wt with the same efficiency and retained it with the same kinetic. However, T. vaporariorum was unable to acquire and retain the PH mutant. Results will also be presented about the ability of both the wt and PH viruses to circulate within insect organs and to accumulate in the head and pro-thorax, after acquisition and incubation, in both B. tabaci and T. vaporariorum.