Unraveling miRNA Post-Transcriptional Regulation Mechanisms behind Eucalyptus globulus Wood Formation

Eucalyptus globulushas great economic, social and ecological importance, occupying about one third of the Portuguese total forest area. In the context of rapid climate changes and limited land availability, the ability to drive wood quality would represent a huge contribution for the Portuguese economy since the use of more adequate and productive genotypes will optimize the exploitation of available plantation areas. Wood complex anatomical, chemical and physical properties are determined upon composite ontogenetic and environmental, requiring the spatio-temporal transcriptional and post-transcriptional regulation of a large number of genes.

In plants, the post-transcriptional regulation by microRNAs plays crucial roles in diverse biological processes such as development, cellular differentiation, and responses to abiotic and biotic stress, including cambium differentiation. These endogenously expressed small RNAs down-regulate the expression of their target genes at the post-transcriptional level predominantly by cleaving their corresponding transcripts

Using two Eucalyptus xylogenesis models (seasonal and tension wood models), we pursued the identification of miRNA and their targets. By combining the sequencing of 15 E.globulus smallRNA libraries to a list of  in silico predicted miRNA candidates identified by themining  E. grandis genome sequence (using the CRAVELA framework; www.cravela.org),  5152 robust candidates (2576 miRNA precursors) were predicted, filtered and ranked according their intrinsic, structural and transcriptional potential features. About 37.7% of these candidates were validated by degradome analysis. Target gene prediction and experimental validation suggested that genes associated with transcription factor regulatory activity, but also those associated to cell wall biosynthesis, are target by these microRNA.

Acknowledgments:

The research was partial funded by Fundação Para a Ciência e a Tecnologia (Portugal) throughout projects PTDC/AGR-GPL/098179/2008, P-KBBE/AGR-GPL/0001/2010 and PTDC/EIA-EIA/122534/2010.