Phi-class glutathione-S-transferase is involved in Dn1-mediated resistance.

Wheat Dn genes afford resistance to the economically important pest, Diuraphis noxia (Kurdjumov, Russian wheat aphid, RWA) and have been the topic of transcriptomic and proteomic studies aimed at unraveling the pathways involved in resistance. The antibiotic resistance conveyed by Dn1 is characterized by a hypersensitive response (HR) followed by systemic acquired resistance (SAR). Although many candidate genes differentially expressed during the Dn1-mediated resistance response have been identified, few have been functionally verified. The aim of this study was to silence three HR-associated candidate genes in Dn1 containing wheat using virus-induced gene silencing (VIGS): thylakoid-associated ascorbate peroxidase (tAPX), phi-class glutathione-S-transferase (TaGSTF6) and superoxide dismutase Cu/Zn (SOD). D. noxia fertility was used as a measure of antibiotic resistance. Silencing of SOD Cu/Zn had little effect on D. noxia fertility, while increased aphid reproduction was recorded on tAPX- and TaGSTF6-silenced plants. However, tAPX-silencing only affected early measurements and did not have a prolonged effect on resistance. TaGSTF6-silenced plants expressed lowered H2 O2 production in resistant wheat under infestation conditions, suggesting that TaGSTF6 and H2 O2 play an integral role in Dn1-mediated D. noxia resistance in wheat plants.

Virus-induced gene silencing of WRKY53 and an inducible phenylalanine ammonia-lyase in wheat reduces aphid resistance.

Although several wheat genes differentially expressed during the Russian wheat aphid resistance response have recently been identified, their requirement for and specific role in resistance remain unclear. Progress in wheat-aphid interaction research is hampered by inadequate collections of mutant germplasm and difficulty in transforming hexaploid wheat. Virus-induced gene silencing (VIGS) technology is emerging as a viable reverse genetics approach in cereal crops. However, the potential of VIGS for determining aphid defence gene function in wheat has not been evaluated. We report on the use of recombinant barley stripe mosaic virus (BSMV) to target and silence a WRKY53 transcription factor and an inducible phenylalanine ammonia-lyase (PAL) gene, both predicted to contribute to aphid defence in a genetically resistant wheat line. After inoculating resistant wheat with the VIGS constructs, transcript abundance was reduced to levels similar to that observed in susceptible wheat. Notably, the level of PAL expression was also suppressed by the WKRY53 construct, suggesting that these genes operate in the same defence response network. Both knockdowns exhibited a susceptible phenotype upon aphid infestation, and aphids feeding on silenced plants exhibited a significant increase in fitness compared to aphids feeding on control plants. Altered plant phenotype and changes in aphid behaviour after silencing imply that WKRY53 and PAL play key roles in generating a successful resistance response. This study is the first report on the successful use of VIGS to investigate genes involved in wheat-insect interactions.