AtDIVARICATA1 promotes flowering through regulating flowering integrators and GA biosynthesis in Arabidopsis.

Arabidopsis R-R-type MYB-like transcription factors AtDIV1 and AtDIV2 (DIVARICATAs) act as critical participants in response to salinity stress. However, their functions in flowering transition are unknown. Here, we reported the function of AtDIV1 in flowering regulation. Protein sequence and 3D structure comparison showed that AtDIV1 was highly conserved, and contained two MYB-like DNA binding domains and one typical 'SHAQKYF/Y' motif. Expression pattern analyses exhibited that AtDIV1 was highly expressed at the bolting stage in Arabidopsis. Overexpression of AtDIV1 in Arabidopsis promoted the flowering of transgenic plants, whereas mutation of AtDIV1 postponed the flowering of div1-1 and div1-2 mutants. Transcriptome analyses revealed that a number of plant hormone and flowering associated genes were up- or down-regulated in transgenic plants. ChIP and EMSA analyses demonstrated that AtDIV1 directly bound to the promoter regions of TEM1, SOC1 and GA3ox1. Further growth experiments in AtDIV1 transgenic plants and div1-1 mutant demonstrated that the content of GA in them was respectively increased and decreased, and the promoted and postponed flowering of them could be respectively rescued with the exogenous application of GA and GA biosynthesis inhibitor paclobutrazol. Our results provide insights into the regulatory mechanism of AtDIV1 mediated flowering via GA signalling pathway in Arabidopsis.