Betalains can be produced in Nicotiana benthamiana roots as a response to AM fungi colonisation.

(a) Schematic of the multigene vectors constructed for inducible betalain expression in N . benthamiana roots where only the first gene of the betalain biosynthesis pathway is controlled by AM symbiosis–specific promoters. Expression of NbPT5b -p1 (b) and NbBCP1b -p1 (c) in whole root systems of N . benthamiana T1 plants 4 weeks after inoculation with Rhizophagus irregularis . Right: Root images are filtered for red colour. (d–g) Confocal microscopy of red NbPT5b-p1 (d and e) and NbBCP1b-p1 (f and g) transgenic root sections which were cut and stained with WGA-FITC to visualise fungal structures. (d and f) colour-filtered for red; (e and g) FITC green fluorescence. Scale bar (b and c), 1 cm; scale bar (d–g), 100 μm. AM, arbuscular mycorrhiza; WGA, wheat germ agglutinin.