Analysis of global gene expression profiles during the flowering initiation process of Lilium × formolongi
The onset of flowering is critical for the reproductive development of plants. Lilium × formolongi is a lily hybrid that flowers within a year after sowing. We successfully identified four important stages during vegetative growth and flowering initiation of L. × formolongi under long day conditions. The plant tissues from the four stages were used in a genome-wide transcriptional analysis to investigate stage-specific changes of gene expression in L. × formolongi. In total, the sequence reads of the four RNA-sequencing libraries were assembled into 52,824 unigenes, of which 37,031 (70.10%) were differentially expressed. The global expression dynamics of the differentially expressed genes were predominant in flowering induction phase I and the floral differentiation stage, but down-regulated in flowering induction phase II. Various transcription factor families relevant to flowering were elucidated, and the members of the MADS-box, SBP and CO-like transcription factor families were the most represented. There were 85 differentially expressed genes relevant to flowering. CONSTANS-LIKE, FLOWERING LOCUS T, TREHALOSE-6-PHOSPHATE SYNTHASE and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE homologs were discovered and may play significant roles in the flowering induction and transition process of L. × formolongi. A putative gene regulatory network, including photoperiod, age-dependent and trehalose-6-phosphate flowering pathways, was constructed. This is the first expression dataset obtained from a transcriptome analysis of photoperiod-mediated flowering pathway in lily, and it is valuable for the exploration of the molecular mechanisms of flowering initiation and the short vegetative stage of L. × formolongi.
KeywordsLilium × formolongi Flowering induction Photoperiod Gene expression RNA-seq
This work has been supported by the National Natural Science Foundation of China (Grant No. 31470106) and the National Forestry Industry Research Special Funds for Public Welfare Projects (Grant No. 201204609).
G-X Jia and M-F Zhang designed the experiments. Y-F Li, M-F Zhang and M Zhang performed the experiments. Y-F Li performed the bioinformatics and the statistical analyses of the transcriptiome and wrote the article. All authors read and approved the final manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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