Post transcriptional gene silencing in controlling species of the Tomato yellow leaf curl virus complex

Tomato yellow leaf curl virus (TYLCV) is a geminivirus, which is transmitted by whitefly (Bemisia tabaci) and causes the most destructive disease of tomato throughout the Mediterranean region and the Middle East. The efficacy of post transcriptional gene silencing (PTGS) to control the disease caused by TYLCV were investigated. Non-coding regions of TYLCV genome were selected to design a silencing trigger construct targeting four species of TYLCV complex. These construct were cloned into an Agrobacterium-binary vector in sense and antisense orientation. These constructs were infiltrated into leaves of tomato and Nicotiana benthamiana. After 12 days, plants were Agro-mediated inoculated with TYLCV, and viral DNA titer determined by DNA hybridization, after 20 days. Viral DNA was detected in 14% of the tomato plants but not in tobacco plants. All plants without the PTGS-constructs had a high viral titer. Similar experiments were performed with viruliferous whiteflies, and the PTGS-construct-infiltrated plants showed resistance to TYLCV, Tomato yellow leaf curl Sardinia virus and the mild strain of TYLCV. A positive correlation existed between the resistance to TYLCV and the accumulation of a 21- to 25-nucleotide siRNAs that corresponds to viral RNA. These data provide compelling evidence that PTGS can be used to engineer geminivirus-resistant plants.