DOAP1 Promotes Flowering in the Orchid Dendrobium Chao Praya Smile

Abstract

<i>APETALA1</i> (<i>AP1</i>) encodes a key MADS-box transcription factor that specifies the floral meristem identity on the flank of the inflorescence meristem, and determines the identity of perianth floral organs in the model plant <i>Arabidopsis thaliana</i>. Orchids are members of the Orchidaceae, one of the largest families of angiosperms. Although the expression patterns of a few <i>AP1</i>-like genes in orchids have been reported, their actual functions in orchid reproductive development are so far largely unknown. In this study, we isolated and characterized an <i>AP1</i> ortholog, <i>DOAP1</i>, from <i>Dendrobium</i> Chao Praya Smile. <i>DOAP1</i> was highly expressed in reproductive tissues, including inflorescence apices and flowers at various developmental stages. Overexpression of <i>DOAP1</i> resulted in early flowering in <i>Arabidopsis</i>, and was able to rescue the floral organ defects of <i>Arabidopsis ap1</i> mutants. Moreover, we successfully created transgenic <i>Dendrobium</i> Chao Praya Smile orchids overexpressing <i>DOAP1</i>, which displayed earlier flowering and earlier termination of inflorescence meristems into floral meristems than wild-type orchids. Our results demonstrate that <i>DOAP1</i> plays an evolutionarily conserved role in promoting flowering and floral meristem specification in the Orchidaceae family.