A Retrotransposon Insertion in the Promoter Causes Harlequin/Black Flowers in Orchids.

The harlequin/black flowers in orchids contain dark purple spots and various pigmentation patterns, which appeared as a new color in 1996. We analyzed this phenotype by microscopy, HPLC, gene functional characterization, genome structure analysis, and transient overexpression system to obtain a better understanding of the black color formation in orchids. Most mesophyll cells of harlequin flowers showed extremely high accumulation of anthocyanins as well as a high expression of MYB11 () as the major regulatory R2R3-MYB transcription factor for regulating the production of the black color.