High Expression of Truncated Viral Rep Protein Confers Resistance to Tomato Yellow Leaf Curl Virus in Transgenic Plants.

A truncated version of the C1 gene of tomato yellow leaf curl geminivirus (TYLCV), encoding the first 210 amino acids of the multifunctional Rep protein, was introduced by Agrobacterium transformation into Lycopersicon esculentum cv. Moneymaker plants under the transcriptional control of an enhanced cauliflower mosaic virus 35S promoter. One R0 plant (line 47) carrying the C1 gene in two loci (A and B) and accumulating the truncated Rep protein (T-Rep), was crossed with either a wild-type plant, or a C1 antisense plant (line 10). The wild type (wt) × 47 progeny were phenotypically homogeneous, contained either A or B locus, expressed high levels of T-Rep protein, had a "curled" phenotype, and were resistant to TYLCV when challenged either by agroinfection or by the vector Bemisia tabaci. In the 10 × 47 progeny, plants carrying only the sense gene behaved like the wt × 47 progeny, while those containing both sense and antisense transgenes did not accumulate the T-Rep protein, showed a normal phenotype, and were not resistant, showing that accumulation of T-Rep protein is required to confer TYLCV resistance. Plants accumulating T-Rep were susceptible to a distinct geminivirus, tomato leaf curl virus (ToLCV-Au).