J. Exp. Bot. http://doi.org/7sn (2015)

Variegation — the presence of different coloured sectors within a single flower or leaf — is a highly valued horticultural trait. Transposable elements are most commonly responsible; unstably disrupting genes involved in pigment production to generate variegated varieties of flowers such as petunia, antirrhinum, carnations, roses and morning glories. However, transposable elements are not the only route to variegation as Yuepeng Han and colleagues at Wuhan Botanical Garden amply demonstrate.

The researchers investigated variegation in the ornamental peach variety Hongbaihuatao. Flowers on a single tree can be red, pink, white or variegated combinations of all three. HPLC analysis of petals showed that the variation in colour was due to differing levels of the anthocyanin cyanadin 3-glucoside, which is abundant in red petals but absent in white. The intermediate pink regions arose when the anthocyanin was confined to the upper and lower epidermal cell layers only.

Well over fifty genes were differentially expressed between red and white regions however only two encoded proteins involved in anthocyanin production and only one, a glutathione S-transferase called Raist, showed sequence differences corresponding to different flower colours. In white petals a two-base-pair insertion created a premature STOP codon. Although no transposable elements play a part in this alteration of Raist, the mechanism by which these spontaneous insertions occur remains to be determined.