MicroRNA comparison between poplar and larch provides insight into the different mechanism of wood formation.

MiRNA transcriptome analysis of different tissues in poplar and larch suggests variant roles of miRNAs in regulating wood formation between two kinds of phyla. Poplar and larch belong to two different phyla. Both are ecological woody species and major resources for wood-related industrial applications. However, wood properties are different between these two species and the molecular basis is largely unknown. In this study, we performed high-throughput sequencing of microRNAs (miRNAs) in the three tissues, xylem, phloem and leaf of Populus alba × Populus glandulosa and Larix kaempferi. Differentially expressed miRNA (DEmiRNA) analysis identified 85 xylem-specific miRNAs in P. alba × P. glandulosa and 158 xylem-specific miRNAs in L. kaempferi. Among 36 common miRNAs, 12 were conserved between the two species. GO and KEGG analyses of the miRNA target genes showed similar metabolism in two species. Through KEGG and BLASTN, we predicted target genes of xylem differentially expressed (DEmiRNA) in the wood formation-related pathways and located DEmiRNAs in these pathways. A network was built for wood formation-related DEmiRNAs, their target genes and orthologous genes in Arabidopsis thaliana. Comparison of DEmiRNA and target gene annotation between P. alba × P. glandulosa and L. kaempferi suggested the different functions of DEmiRNAs and divergent mechanism in wood formation between two species, providing knowledge to understand wood formation mechanism in gymnosperm and angiosperm woody plants.