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Molecular mechanisms in the first step of aba-mediated response in Coffea ssp.

Guitton Cotta M.. 2017. Montpellier : Montpellier SupAgro, 176 p.. Thèse de doctorat -- Biologie intégrative des plantes.

Abscisic acid (ABA) is a phytohormone 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, in volving intracellular ABA receptors (PYR/PYL/RCARs) interacting with PP2Cs phosphatases and SnRK2 protein kinases regulating this tripartite protein system. The goal of this study was to identify and characterize for the first time the orthologs genes of this tripartite system in Coffea. For this purpose, protein sequences from A rabidopsis , citrus, rice, grape, tomato and potato were chosen as query to search orthologous genes in the Coffee Genome Hub ( Differential expression in tissues as leaves, seeds, roots and floral organs was checked through in silico analyses. In vivo gene expression analyses were also performed by RT-qPCR in leaves and roots of drought-tolerant (D T 14, 73 and 120) and drought-susceptible (D S 22) C. canephora Conilon clones submitted (or not) to drought. The expression profiles of the tripartite system CcPYL-PP2C-SnRK2 genes were also analyzed in leaves of C. arabica (Ca) and C. canephora (Cc) plants grow n under hydroponic condition and submitted to exogenous ABA treatment (500 ?M). This approach allowed the identification and characterization of 24 candidate genes (9 PYL/RCARs, 6 PP2Cs and 9 SnRK2s) in Cc genome. The protein motifs identified in the predict coffee sequences enabled characterize these genes as family's members of PYL/RCARs receptors, PP2Cs phosphatases or SnRK2 kinases of the ABA-dependent response pathway. These families were functionally annotated in the Cc genome. In vivo analyses revealed that eight genes were up-regulated under drought conditions in both leaves and root s tissues. On the other hand, CcPYL4 was down-regulated under water deficit in both tissues for all clones. Among them, three genes coding p

Mots-clés : coffea

Thématique : Génétique et amélioration des plantes; Physiologie et biochimie végétales; Troubles divers des plantes

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