Résumé
The Coffea genus represents a major agricultural commodity in world trade. Nowadays, drought and elevated temperatures are the major climatic limitations for coffee production. These variations also influence biochemical composition of beans, affecting directly the final cup quality. There is genetic variability within the Coffea genus that could be used to increase drought tolerance and generate coffee varieties better adapted to climatic variations. Abscisic acid (ABA) is a vital plant hormone acting as central regulator that protects plants against abiotic stresses such as drought. Recently, novel intracellular ABA receptors (PYL/RCARs) involved in ABA sensing and signaling have been identified in several species. A mechanism of ABA transduction has been proposed, involving PYR/PYL/RCARs receptors interacting with PP2Cs phosphatases and SnRK2 protein kinases. The goal of this study was to identify and characterize ortholog genes of this tripartite system in Coffea sp. For this purpose, protein sequences from Arabidopsis, citrus, rice, grape, and tomato were chosen as query to search ortholog genes in the coffee-sequence database. Using 51 PYR/PYL/RCAR sequences from those plant species, it was possible to identify 9 sequences for ABA receptors in coffee. Likewise, the 40 and 29 sequences query resulted in 6 and 9 similar sequences of PP2Cs and SnRK2 specific to ABA in Coffea sp. The 24 genes isolated, that belong to the tripartite system of the coffee's ABA pathway, showed in silico differential expression in tissues as leaves, seeds, roots and floral organs. Polymorphisms were found among the orthologs and homeologs genes. All analyses allowed the identification in C. arabica genome of sequences variations between the two ancestral diploid sub-genomes, C. canephora (CaCc) and C. eugenioides (CaCe). Further analyses will predict the functional effect of these polymorphisms in protein structure in different coffee species. All these evidences will also help us to identify the genetic determinism of drought tolerance essential to obtain molecular markers that could be used in coffeebreeding programs. Work supported by CAPES-COFECUB, Consórcio Pesquisa Café and INCT-Café (CNPq/FAPEMIG). (Texte intégral)