Distinct patterns of pigment suppression are produced by allelic sense and antisense chalcone synthase transgenes in petunia flowers

Abstract

Summary A single‐copy sense Chalcone synthase ( Chs ) transgene driven by a strong promoter and producing a fully translatable transcript was converted to an allelic antisense Chs transgene by Cre ‐lox ‐mediated DNA recombination in petunia. The sense Chs allele suppressed flower pigmentation in a simple pattern determined by cells at the junctions between adjacent petals, as is typical of single‐copy sense Chs transgenes of this type, whereas the antisense Chs allele produced a different pattern of Chs suppression with white petal edges and reduced pigmentation throughout the petal limbs, as is typical of antisense Chs transgenes. In plants carrying a lox‐ flanked Chs transgene, the presence of Cre protein can cause both sense‐specific and antisense‐specific patterns to be superimposed in the same flower, suggesting that sense and antisense suppression by single‐copy transgenes are mediated by different mechanisms or occur in different cellular or developmental compartments. The presence of Cre also causes the production of numerous, non‐clonal white spots, suggesting that the turnover state is not cell‐autonomous.