Functional analysis of a lily SHORT VEGETATIVE PHASE ortholog in flowering transition and floral development

Lilium is a commercially important genus of bulbous flowers, investigating the flowering molecular mechanisms is important for flowering regulation of lily. MADS-box SHORT VEGETATIVE PHASE (SVP) orthologs are involved in the flowering transition and floral organ differentiation in many plants. In this study, we identified an SVP ortholog from L. x formolongi (LfSVP), which was closely related to Arabidopsis SVP according to phylogenetic analysis. Tissue-specific expression patterns indicated that LfSVP expression levels peaked in the leaves and showed low expression levels in flowering tepals. Stage-dependent expression patterns of LfSVP showed high transcription level in the flowering induction stage under different photoperiods and exhibited transcription peak in the floral budding development stage under long days. Overexpressed LfSVP led to delayed flowering and floral organ defects in Arabidopsis independent of photoperiod. Tobacco rattle virus -induced gene silencing of LfSVP caused a strongly earlier flowering time and floral organ defects of L. x formolongi. Moreover, LfSVP can interact with L. x formolongi APETALA1 (AP1) in both yeast and tobacco cells, and the two may interact to regulate floral organ differentiation. In conclusion, LfSVP is a flowering repressor and may be involved in the regulation of floral organ differentiation. This study will be helpful for the molecular breeding of short-life-period and rich floral patterns lily varieties.