Transcriptional repressor AGL79 positively regulates flowering time in Arabidopsis.

The MADS-box gene family is widely distributed in higher plants and the members of the angiosperm-specific APETALA1/FRUITFULL (AP1/FUL) subfamily plays important roles in the regulation of plant reproductive development. Recent studies revealed that the AP1/FUL subfamily member Dt2, VEGETATIVE1/PsFRUITFULc (VEG1/PsFULc) and MtFRUITFULc (MtFULc) are essential for the stem growth, branching and inflorescence development in legume species soybean (Glycine max), pea (Pisum sativum) and Medicago truncatula. However, the biological function of their homologue in Arabidopsis thaliana, AGAMOUS-LIKE 79 (AGL79), has not been well elucidated. In this study, we investigated the developmental roles of Arabidopsis AGL79 by CRISPR/Cas9-mutagenesis and molecular and physiological analyses. We found that AGL79 mainly acts as a transcriptional repressor and positively regulates Arabidopsis flowering time. We further revealed that AGL79 interacts with SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1) and represses the expression of TERMINAL FLOWER 1 (TFL1). Our results demonstrated the AGL79-mediated flowering regulation in Arabidopsis and added an additional layer of complexity to the understanding of flowering time regulation in dicot plants.