Ectopic expression of an AtBMI1a homolog from Vitis vinifera accelerates flowering time in transgenic Arabidopsis

BMI1 is the main component of the Polycomb Group Complex 1 (PRC1), which functions as an important epigenetic inhibitor of various regulatory genes associated with shoot apical meristem, embryonic development, flowering, senescence and so on. However, its role in the regulation of grapevine development is still unclear. In order to explore the function of VvBMI1a gene in the regulation of flowering in Vitis vinifera ‘Cabernet Sauvignon’, the subcellular localization, expression pattern, yeast two-hybrid, two-molecule fluorescence complementation and flowering time of transgenic Arabidopsis were analyzed. The results showed that VvBMI1a, a member of RING domain-containing proteins family from grapevine (Vitis vinifera), is involved in controlling plant flowering time. Expression of VvBMI1a was abundant in the shoot tips and inflorescence meristems of grapevine. VvBMI1a protein is localized in the nucleus. VvBMI1a could interact with VvRING1a protein which belonged to PRC1. Phenotypic analysis showed that VvBMI1a over-expression lines had earlier flowering time than wild-type plants under long-day (LD) conditions. Further analysis by qRT-PCR and transcriptome suggests that both the suppression of FLC and activation of FT, SOC1, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 5 (SPL5), AGL8 were observed in VvBMI1a-overexpressing lines, resulting in early flowering. Our results provide the evidence demonstrating the effectiveness of manipulating VvBMI1a to alter the flowering time of plants. In a word, ectopic overexpression of VvBMI1a inhibited the expression of FLC, activated the expression of FT, SPL5, AGL8 to alter the flowering time of Arabidopsis plants.