ZmSOC1, an MADS-Box Transcription Factor from Zea mays, Promotes Flowering in Arabidopsis

Zea mays is an economically important crop, but its molecular mechanism of flowering remains largely uncharacterized. The gene, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), integrates multiple flowering signals to regulate floral transition in Arabidopsis. In this study, ZmSOC1 was isolated from Zea mays. Sequence alignment and phylogenetic analysis demonstrated that the ZmSOC1 protein contained a highly conserved MADS domain and a typical SOC1 motif. ZmSOC1 protein was localized in the nucleus in protoplasts and showed no transcriptional activation activity in yeast cells. ZmSOC1 was highly expressed in maize reproductive organs, including filaments, ear and endosperm, but expression was very low in embryos; on the other hand, the abiotic stresses could repress ZmSOC1 expression. Overexpression of ZmSOC1 resulted in early flowering in Arabidopsis through increasing the expression of AtLFY and AtAP1. Overall, these results suggest that ZmSOC1 is a flowering promoter in Arabidopsis.