Résumé
Abscisic acid (ABA) pathway is aphytohormone universally conserved in land plants which coordinates several aspects of the plant response to water deficit such as root architecture, seed dormancy and regulation of stomatal closure. A mechanism of ABA signal transduction has been proposed, evolving intracellular ABA receptors (PYR/PYL/RCARs) interacting with PP2Cs phosphatases and SnRK2 protein kinases regulating this tripartite protein system. Rationale. The goal of this study was to identify and characterize for the first time the orthologs genes of this tripartite system in Coffea canephora. Methods. For this purpose, protein sequences from Arabidopsis, citrus, rice, grape, tomato and potato were chosen as query to search orthologous genes in the Coffee Genome Hub (http://coffee-genome.org/). Differential expression in tissues as leaves, seeds, roots and floral organs was checked through in silky analyses. In vivo gene expression analyses were also performed by RT-qPCR in leaves and roots of drought-tolerant (DT 14, 73 and 120) and drought-susceptible (Ds 22) C canephora Conilon clones submitted or not) to drought. Results. This approach allowed the identification and characterization of 17 candidate genes (9 PYL/RCARs, 6 PP2Cs and 2 SnRK2s) in C. canephora genome. The protein motifs identified in predict coffee sequences enabled characterize these genes as family's members of PYL/RCARs receptors, PP2Cs phosphatases or SnRK2 kinases of the ABA response pathway. These families were functionally annotated in the C. canephora genome. In vivo analyses revealed that eight genes are up-regulated under drought conditions in both leaves and roots tissues. Among them, three genes coding phosphatases were expressed in all (DT and Ds) clones therefore suggesting that they were activated as a general response to cope with drought stress. However, two other phosphatase coding genes were up-regulated only in the DT clones, suggesting that they constituted key-genes for drought tolerance in these clones. The DT clones also showed differential gene expression profiles for five other genes therefore reinforcing the idea that multiple biological mechanisms are involved drought tolerance in C. canephora. Conclusions and Perspectives. All these evidences will help us to identify the genetic determinism of drought tolerance through ABA pathway essential to obtain molecular markers that could be used in coffee breeding programs. (Texte intégral)