Small RNA and degradome analyses reveal regulatory roles of miRNAs in vascular cambium development in Cryptomeria fortunei

The vascular cambium activity of trees directly affects the yield and quality of forest products. Therefore, studying the laws governing vascular cambium activity in Cryptomeria fortunei, a species mainly used for wood production, is important. miRNAs regulate target gene expression and play an important role in plant growth and development, but the role of miRNAs in C. fortunei vascular cambium growth remains poorly understood. Here, small RNA (sRNA) and degradome libraries were constructed for C. fortunei vascular cambium at five different growth stages. A total of 1064 miRNAs (859 known and 205 novel miRNAs), including 266 differentially expressed miRNAs (DEMs), were identified by sRNA sequencing, and 4215 targets of 843 miRNAs were identified by degradome analysis. These targets were enriched in metabolism (e.g., phenylpropanoid biosynthesis), genetic information processing and signal transduction (e.g., plant hormone signal transduction) pathways during vascular cambium development. We obtained 365 differentially expressed target pairs and constructed a regulatory network of 111 annotated negatively regulated target pairs. The blue module was identified as a key module through weighted DEM coexpression network analysis, and seven negatively regulated target pairs (pabmiR159g/aly-miR397a-5p/pab-miR397a/novel23_mature-MYB, novel12_star-UGT72B1 and smo-miR1083/pabmiR1083-GARP-ARR-B) were considered as key regulators of C. fortunei vascular cambium growth. This study provides important miRNA and target data related to C. fortunei vascular cambium growth. These results increase the understanding of the posttranscriptional regulatory mechanisms of vascular cambium development in conifers and provide important references for the genetic improvement of wood production in plants.

Automated summary

This study identified numerous miRNAs and target genes involved in the vascular cambium development of Cryptomeria fortunei through sRNA and degradome sequencing. The results revealed the regulatory roles of these miRNAs and constructed a regulatory network and key module. The findings provide important insights into the posttranscriptional regulatory mechanisms of vascular cambium development in conifers and offer references for genetic improvement of wood production in plants.