Transcription coactivator A rabidopsis ANGUSTIFOLIA 3 modulates anthocyanin accumulation and light‐induced root elongation through transrepression of C onstitutive P hotomorphogenic1

ANGUSTIFOLIA 3 ( AN 3), a transcription coactivator, is implicated in modulating cell proliferation. In this study, I found that AN 3 is a novel regulator of anthocyanin biosynthesis and light‐induced root elongation. Seedlings and seeds lacking AN 3 activity presented significantly reduced anthocyanin accumulation and light‐induced root elongation, whereas those of transgenic plants harbouring the 35 S : AN 3 construct exhibited increased anthocyanin accumulation. AN 3 is required for the proper expression of other genes that affect anthocyanin accumulation and light‐induced root elongation, C onstitutive   P hotomorphogenic1 ( COP 1 ), encoding a RING motif – containing E3 ubiquitin ligase. AN 3 was associated with COP 1 promoter in vivo . Thus, AN 3 may act with other proteins that bind to COP 1 promoter to promote anthocyanin accumulation and inhibit light‐induced root elongation.