Ectopic expression of the Aechmea fasciata APETALA2 gene AfAP2-2 reduces seed size and delays flowering in Arabidopsis

Abstract The Bromeliaceae family, which is distributed pantropically, is one of the most morphologically diverse families. Except for the edible pineapple ( Ananas comosus ), the vast majority of bromeliads cultivated worldwide are appreciated mainly for their ornamental value. As subtropical and tropical flowering plants, these bromeliads, among with Aechmea fasciata , have significant economic importance. However, the molecular mechanism of flowering in bromeliads remains unrevealed. In this study, an APETALA2 (AP2) homologue, AfAP2-2, which belongs to the AP2/ethylene response element binding protein (AP2/EREBP) transcription factor superfamily, was identified in A. fasciata . AfAP2-2 contains two conserved AP2 domains and is a nuclear-localized transactivator. The expression level of AfAP2-2 was predominantly higher in vegetative organs of the reproductive phase than in those of the vegetative phase. Ectopic expression of AfAP2-2 in Arabidopsis specifically delayed flowering in short-day (SD) conditions. Furthermore, the size and weight of seeds of AfAP2-2-overexpressing Arabidopsis plants were significantly reduced compared to those of the wild type (WT). Our findings suggest that AfAP2-2 might be a negative regulator of flowering and seed size and weight. These results may help facilitate the molecular breeding of bromeliads.