Comparative proteomic analysis of Tunisian barley landraces in response to salinity at the tillering stage.

Salinity is one of the major abiotic constraints impairing barley production. Tunisian landraces constitute a valuable reservoir of useful traits for breeding programs. Therefore, exploring the molecular mechanisms underlying salinity tolerance is of great interest. Here, the proteome response to salt stress of the 4th leaf at the tillering stage was assessed in two barley accessions, Barrage Mellegue (BM, tolerant) and Saouef (S, sensitive). Results led to the selection of differentially abundant proteins (DAP), including 20 and 49 genotype specific salt responsive proteins, respectively, and 12 common ones. Moreover, 10 biological functions were associated to salinity response, including photosynthesis. Indeed, the RBCS protein was surabundant only in the tolerant genotype. Nevertheless, 8 proteins including PSB28, PPD3, TLP16.5, MgCh40, TLP17.4, Rubisco, OEE and PSBH were less abundant in the sensitive genotype, although invariable in the tolerant BM. Therefore, signaling, nucleic acid binding, protein synthesis, ROS scavenging and photosynthesis might be the main biological processes related to salinity tolerance in barley. In fact, based on hierarchical classification and protein-protein interactions, ES2A, Cp31 BHv, PRX II, Srpsus2, RBCS and RLP12 (RPS50) proteins were identified as key candidates. Our findings suggest that BM can mitigate the negative effect of salinity at the tillering stage by inducing signal transduction pathway elements, reducing nucleic acid binding process, regulating ROS scavenging system, decreasing protein synthesis and, maintaining the photosynthesis system. Our results would serve as a useful source for deciphering the mechanisms governing salt stress tolerance at all stages of development, which is essential for barley breeding programs.