Rose long non-coding RNA lncWD83 promotes flowering by modulating ubiquitination of the floral repressor RcMYC2L

Abstract Long noncoding RNAs (lncRNAs) play important roles in various signaling pathways in vascular plants. However, the crosstalk between lncRNAs and E3 ubiquitin ligases has been barely reported. In this study, we demonstrate that the lncRNA lncWD83 from rose (Rosa chinensis) ‘Old blush’ activates flowering by modulating the ubiquitination of the floral repressor MYC2 LIKE (RcMYC2L). Flowering was substantially delayed in rose by virus-induced gene silencing of lncWD83. In an in vitro pull-down assay, lncWD83 associated with PLANT U-BOX PROTEIN 11 (PUB11), a U-box-containing E3 ubiquitin ligase. Seedlings with knocked down RcPUB11 transcripts phenocopied the later-flowering phenotype of lncWD83-silenced seedlings. RcMYC2L physically interacted with RcPUB11 and was ubiquitinated in an RcPUB11-dependent manner in vitro. Accordingly, silencing RcMYC2L fully reversed the later-flowering phenotype resulting from RcPUB11 knockdown. Furthermore, RcMYC2L bound to G-box-related motifs in the FLOWERING LOCUS T (RcFT) promoter and repressed its transcription. However, RcPUB11 alleviated this repression of RcFT expression via proteasomal degradation of RcMYC2L, and lncWD83 enhanced this degradation by associating with RcPUB11. Therefore, lncWD83 promotes flowering by modulating the ubiquitination of the floral repressor RcMYC2L in rose plants. These findings reveal a distinct regulatory mechanism for an lncRNA in facilitating ubiquitin-mediated proteolysis to regulate rose flowering.