We are testing is the ability of trans-dominant mutant versions of the geminivirus replication proteins – AL1 and AL3 – to interfere with viral replication in transgenic plants. We generated transgenic Nicotiana benthamiana plants that co-express trans-dominant mutant versions of TGMV AL1 and AL3. It has been difficult to express AL1 stably in plants, most likely because of its ability to interact with pRBR and modify host cell cycle and developmental controls. To overcome this problem, we used a mutant version of AL1 that is also impaired pRBR binding.

Infectivity studies identified plants that are phenotypically normal, express the transgene through at least the T4 generation, and are immune to TGMV infection. Because the mutations in AL1 and AL3 are in highly conserved residues, this technology can be readily transferred to other geminivirus/host combinations as near term solution to geminivirus resistance. We are collaborating with Jane Polston (University of Florida) and Moshi Lapidot (Volcani Center, Israel) to introduce similar expression cassettes into tomato for resistance studies with TYLCV and ToMoV.

This research is funded by grants from NRI-USDA and the BARD Foundation.