Integrated RNA and miRNA sequencing analysis reveals a complex regulatory network of Magnolia sieboldii seed germination

Magnolia sieboldii K. Koch (M. sieboldii) is a deciduous Chinese tree species of the Magnoliaceae family with high ornamental, medicinal, and economic benefits. The germination of M. sieboldii seeds under natural conditions is extremely difficult, thereby hindering the cultivation and breeding of this important species. The molecular mechanisms underlying M. sieboldii seed germination remain unclear due to the lack of genomic and transcriptomic resources. Here, we integrated both mRNA and miRNA sequencing to identify the genes and pathways related to M. sieboldii germination. A comprehensive full-length transcriptome containing 158,083 high-quality unigenes was obtained by single-molecule real-time (SMRT) sequencing technology. We identified a total of 13,877 genes that were differentially expressed between non-germinated and germinated seeds. These genes were mainly involved in plant hormone signal transduction and diverse metabolic pathways such as those involving lipids, sugars, and amino acids. Our results also identified a complex regulatory network between miRNAs and their target genes. Taken together, we present the first transcriptome of M. sieboldii and provide key genes and pathways associated with seed germination for further characterization. Future studies of the molecular basis of seed germination will facilitate the genetic improvement M. sieboldii.