Résumé
Polyploidy occurs throughout the evolutionary history of many plants, giving rise to novel phenotypes and leading to ecological diversification and colonization of new niches. Coffea arabica a recent allopolyploid between two low divergent diploid species, Coffea eugenioides and Coffea canephora, can be grown in regions with marked variations in thermal amplitude while the parental species are less adapted to temperature variations. To assess the contribution of subgenomes to the C. arabica transcriptome and its variation in relation to the adaptation to variable culture conditions, the transcriptome of leaves of C. arabica plants grown in two contrasted thermal regimes were examined using RNA sequencing (RNA-seq) approach. Then the relative homoeologous gene expression was compared to the relative expression between the modern-day diploid progenitor species. Whatever the growing conditions, 65% of the studied genes showed equivalent level of homoeologous gene expression, and for a large majority (92%), the relative homoeologous gene expression between both growing conditions varied less than 10 %. In C. arabica growing conditions do not disrupt the relative homoeologous gene expression and the overall gene expression appears to be regulated by intertwined mechanisms. Unlike others allopolyploids analyzed previously, C. arabica showed no preferentially expressed subgenome illustrating the interest of considering the age of the allopolyploidization event and the evolutionary divergence of progenitor species when studying allopolyploidy. (Résumé d'auteur)