MicroRNA-Mediated Post-transcriptional Regulation of Wood Property Traits in Eucalyptus tereticornis

Eucalyptus is a fast growing hardwood tree species preferred for its wood properties which are suitable for paper and pulp industries. The transcriptional regulation governing secondary wood formation in Eucalyptus is extensively studied while the role of post-transcriptional mechanism determining wood phenotypes is not well documented. The present study aimed at understanding the miRNA-mediated regulation of secondary development in Eucalyptus tereticornis. Transcriptome-wide identification of miRNAs in wood tissues predicted a total of 266 conserved mature miRNA members belonging to 76 families. Et-miR156 was the most abundant family followed by Et-miR166 and Et-miR167. Majority of the gene targets of miRNAs were transcription factors including AP2, GRF, TCP, ARF, bHLH, bZIP, HD-ZIP, MYB, NAC, SBP, WRKY and Zinc finger. Further, 102 miRNA members were predicted to target genes from the cellulose and lignin biosynthetic pathways. Additionally, the expression patterns of four miRNAs (Et-miR156d-5p, Et-miR156a, Et-miR156b-5p, and Et-miR159b) and their gene targets were validated in eight individuals with contrasting cellulose and lignin content to predict the role of miRNAs in governing wood property traits. In summary, the present study has predicted potential miRNA targets which may regulate wood phenotypes in E. tereticornis and has also generated valuable genomic resource for enhancing wood quality through marker assisted selection and gene editing strategies.