Résumé
RATIONALE Polyploidy impacts the diversity of plant species, giving rise to novel phenotypes and leading to ecological diversification. Many phenotypic changes with a high adaptive value, concerning vigor, biomass and adaptation to biotic and abiotic stress, would enable the polyploids to occupy new ecological niches and seem to be conducive to their use in agriculture. METHODS In order to observe adaptive and evolutionary capacities of polyploids, we compared the growth, primary metabolism and transcriptomic expression level in the leaves of the newly formed allotetraploid Coffea arabica species compared with its two diploid parental species (Coffea eugenioides and Coffea canephora), exposed to four thermal regimes (TRs; 18-14, 23-19, 28-24 and 33-29C). RESULTS The growth rate of the allopolyploid C. arabica was similar to that of C. canephora under the hottest TR and that of C. eugenioides under the coldest TR. For metabolite contents measured at the hottest TR, the allopolyploid showed similar behavior to C. canephora, the parent which tolerates higher growth temperatures in the natural environment. However, at the coldest TR, the allopolyploid displayed higher sucrose, raffinose and ABA contents than those of its two parents and similar linolenic acid leaf composition and Chi content to those of C. eugenioides. At the gene expression level, few differences between the allopolyploid and its parents were observed for studied genes linked to photosynthesis, respiration and the circadian clock, whereas genes linked to redox activity showed a greater capacity of the allopolyploid for homeostasis. Finally, we found that the overall transcriptional response to TRs of the allopolyploid was more homeostatic compared with its parents. CONCLUSIONS & PERSPECTIVES This better transcriptional homeostasis of the allopolyploid C. arabica afforded a greater phenotypic homeostasis when faced with environments that are unsuited to the diploid parental species.