Key microRNAs and target genes involved in regulating maturation of Lilium

Lilium is a kind of ornamental bulb plant, but the juvenile stage is long, which brings inconvenience to the production. In this study, bulbs of Lilium OT 'Robina' were treated in a period of lowered temperature to induce phase transition. Small RNA and degradome were sequenced.In small RNA sequencing, a total of 92 known miRNAs were selected and 86 novel miRNAs were predicted. Combined with degradome sequencing, 161 miRNAs could be identified as targets. 29 known miRNAs were differentially expressed, including 16 up-regulated miRNAs and 13 down-regulated miRNAs. Lbr-miR156a showed a significantly down-regulated expression trend, and the target genes of Lbr-miR156a were accurately identified as LbrSPL3 and LbrSPL16 combined with degradome sequencing.Phylogenetic analysis showed that LbrSPL3 and LbrSPL16 had high homology with other plant SPLs. Subcellular localization and transcriptional activation experiments confirmed that LbrSPL3 and LbrSPL16 were mainly located in the nucleus and had transcriptional activity. in situ hybridization results showed that the expressions of LbrSPL3 and LbrSPL16 were increased after temperature change. Functional verification experiments of transgenic plants showed that overexpression of LbrSPL3 and LbrSPL16 could promote plant phase change, while overexpression of Lbr-miR156a could inhibit this process. These results are helpful to elucidate the mechanism of phase transition regulation in Lilium and provide reference for other corm flower breeding studies.