A virus‐induced gene‐silencing system for functional genetics in a betalainic species, Amaranthus tricolor (Amaranthaceae)

Premise of the Study Research in Amaranthaceae could be accelerated by developing methods for targeted gene silencing. Most amaranths, including Amaranthus tricolor , produce betalains. However, the physiological and ecological roles of these pigments are uncertain. We sought to establish a virus‐induced gene‐silencing ( VIGS ) method for amaranths, using silencing of betalain pigments as a proof‐of‐principle. Methods We targeted Atri CYP 76 AD 1 , a putative cytochrome P450 component of the betalain biosynthetic pathway, using VIGS , and compared two different methods of introducing the VIGS construct into plants. We measured transcript abundance and concentrations of betalains and their l ‐ DOPA precursor in VIGS ‐treated plants, and compared these to controls. Results We observed that when Atri CYP 76 AD 1 was targeted by VIGS in normally red plants, Atri CYP 76 AD 1 and the related genes Atri CYP 76 AD 6 and Atri CYP 76 AD 5 had diminished transcript abundance. Furthermore, newly emergent petioles and leaves of VIGS ‐treated plants appeared green, betacyanin accumulation was strongly reduced, and l ‐ DOPA accumulation was increased. No betaxanthin could be detected in this variety of A. tricolor , either before or after VIGS treatment. Discussion These results help to establish the genetic basis of betalain synthesis in amaranths. Furthermore, this is the first report of VIGS in amaranths and demonstrates the potential of this technique for basic and applied research in these species.