Fig. 5.

Diversity of flower colour patterning and developmental patterns. (A) Schematics of known flower colour patterns. The central flower has unpigmented petals. The top-left schematic shows a monocolour flower, with pink pigmentation in all petals. Moving clockwise, the bicolour flower has pigmented (pink) and unpigmented regions to each petal. Venation patterning is shown next, with pink pigmentation over the veins of the petals. Below that, a flower is shown with pink pigmentation and darker pigmented spots. At bottom-right, the flower is blue because chemical modification has changed the absorption spectrum of the pigment. The bottom-left schematic shows a flower in which only one petal is pigmented yellow, providing an orientation petal to aid pollinator foraging. The next flower has two different pigment colours on each petal, creating a central bullseye pattern. The final flower has pink pigment but an unpigmented region over the midrib of each petal, creating stripes. (B) Regulation of pigment synthesis in Clarkia gracilis (B.1) and Mimulus lewisii (B.2). C. gracilis has four paralogues of R2R3 MYB transcription factors of which three, MYB6, MYB11 and MYB12, show expression patterns associated with the background pink pigment production (MYB11, distal part of the petal; MYB12, proximal part of the petal; MYB6, whole petal), while MYB1 is only associated with the red spot region. Furthermore, MYB12 exclusively regulates pigment production in the white region at the base of the petals. In M. lewisii, PELAN (PEL) forms an MBW complex (with an unknown bHLH and WDR partner) to produce the pink colour in petals, while RCP1 inhibits and restricts PEL in the ventral petal ridges and, through a double negative regulation of YUP and RCP2, produces yellow pigment. Meanwhile, a reaction-diffusion gradient comprised of NEGAN (NEG) and its R3 MYB repressor RTO, produces the red spots on the ventral petal ridges.