A RNAseq Approach to Decipher the Molecular Mechanisms Involved in Dormancy Regulation in the Fagaceae Family

In perennial species the seasonal cycling is divided in two main steps: a growing period from spring to late summer and a non growing period in winter to prevent buds from cold injury. The non-growing period is called dormancy.  Dormancy comprised two phases: (i) endodormancy, the deepest state of dormancy induced by the meristem itself, and (ii) ecodormancy when unfavorable environmental conditions prevent bud burst in late winter and spring. This dormancy cycle has been shown to be strongly affected by climatic change, higher temperatures having a negative impact on endodormancy and a positive effect on ecodormancy. In forest trees, the molecular mechanisms involved both in dormancy induction and regulation are poorly understood. To fill this gap, we set up a RNAseq approach in two fagaceae species (Oak and Beech). First, we harvested terminal buds at three time points:  endodormancy, ecodormancy and just before bud burst (swelling buds). Then, transcriptome was sequenced using an illumina sequencing approach and assembled. Following mapping of the reads onto the unigenes, contigs covered by more than 5 reads were kept for digital expression analysis. Differentially expressed genes were then used for Gene-set Enrichment Analysis (GSEA) and Sub-network Enrichment Analysis (SNEA) using Ariadne Pathway Studio 9 Software. Our results showed that the molecular mechanisms involved in endormancy and ecodormancy are comparable in oak and beech while those involved in buds swelling are opposite suggesting different flushing strategy in the two analyzed species.