Characteristics of PoVIN3, a Key Gene of Vernalization Pathway, Affects Flowering Time

The tree peony (Paeonia section Moutan DC.) is the candidate flower in China, with abundant germplasm resources and high ornamental value. However, the short and concentrated flowering period severely restricted the improvement of the economic value of tree peonies. Based on the full-length transcriptome database of tree peonies, the PoVIN3 (GenBank ID: OP341879), involved in the flowering regulation of tree peonies were identified and cloned for the first time. The PoVIN3 was also characterized by bioinformatics methods, quantitative real-time PCR (qRT-PCR), and the establishment of a transgenic system. The expression levels of PoVIN3 in seven different petals developmental stages were the highest at the initial flowering stage of the variant cultivar of Paeonia ostii 'Fengdan,' the initial decay stage of the normal flowering Paeonia ostii 'Fengdan,' and the half opening stage of the late flowering Paeonia suffruticosa 'Lianhe.' Tissue-specific expression analysis showed that the relative expression levels of PoVIN3 were the highest in sepals of both normal flowering Paeonia ostii 'Fengdan' and the late flowering Paeonia suffruticosa 'Lianhe,' and the highest expression was in stamens of early flowering mutant Paeonia ostii 'Fengdan.' In addition, the flowering time of pCAMBIA2300-PoVIN3 transgenic plants was significantly earlier than that of the wild-type, indicating that PoVIN3 could promote plant flowering. The results provide a theoretical basis for exploring the role of PoVIN3 in the regulation of flowering in tree peonies.