RNAi-Mediated Silencing of Endogenous Wheat Genes EIF(Iso)4E-2 and EIF4G Induce Resistance to Multiple RNA Viruses in Transgenic Wheat

Wheat (Triticum aestivum L.) lacks sources of effective resistance to the potyviruses Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV). Potyviruses use host eukaryotic initiation factors (eIFs) to facilitate initial translation of their genomes, and many plant virus resistance genes are due to mutations in eIFs. Therefore, we hypothesized that silencing TaeIF(iso)4E and TaeIF4G would provide effective and broad-spectrum virus resistance. Three transgenic wheat lines with an RNA interference (RNAi) hairpin construct targeting TaeIF(iso)4E and four lines with a hairpin construct targeting TaeIF4G were recovered through wheat transformation. Early generation lines were found to be resistant to WSMV and TriMV, and co-inoculation of both. The lines were selfed to the T-5 generation to insure transgene stability, as well as crossed onto the hard red winter wheat cultivar 'Karl 92' to test the RNAi constructs in a more adapted genetic background. Phenotypically, transgenic lines were found to be resistant to WSMV, TriMV, and mixed infections of both, were resistant to Soil-borne wheat mosaic virus, and demonstrated a significant reduction in Barley yellow dwarf virus infection. The RNAi effectiveness on viral RNA was evaluated using reverse transcription quantitative polymerase chain reaction (PCR). An 18-fold reduction in WSMV and TriMV viral RNA was found in the T-5 transgenic lines when compared with control plants. Viral RNA reduction was also found in the F-1, and BC1F1 crosses to Karl 92. These results demonstrate that a single, endogenously derived transgene in wheat can provide resistance to multiple viruses and provides a proof of concept for future gene editing.