Abordagem ômica integrada na investigação da aclimatação ao estresse salino induzida pela ativação do retículo endoplasmático em feijão-caupi (Vigna unguiculata [L.] Walp)

Abstract

Salinity represents one of the main limiting factors for agricultural productivity, affecting ionic homeostasis, redox balance, metabolism, and plant growth. Although the endoplasmic reticulum (ER) is recognized as an important hub for integrating cellular signals under stress conditions, the mechanisms by which its activation can modulate salt tolerance in cowpea (Vigna unguiculata [L.] Walp.) remain incompletely understood. This thesis investigated whether the controlled stimulation of adaptive endoplasmic reticulum signaling, through transient activation of the unfolded protein response (UPR) induced by tunicamycin (TM), could function as a priming mechanism, increasing the efficiency of acclimation to salinity. Foliar application of TM was selected to induce systemic ER signaling without directly altering ion uptake by roots, allowing the controlled activation of adaptive pathways prior to salt exposure. An integrative and temporal approach was employed, combining physiological analyses, Na+ and K+ quantification, hydrogen peroxide (H2O2) determination, qPCR-based gene expression analysis of unfolded protein response (UPR) markers and ion transporters, as well as metabolomic, lipidomic, and quantitative proteomic analyses in leaves. The results demonstrated that TM priming significantly attenuated the deleterious effects of NaCl, promoting improved photosynthetic performance and enhanced plant growth. A reduction in Na+ accumulation in the shoot, greater K+ retention, and increased ionic sequestration in roots were observed, indicating improved ionic homeostasis. TM application induced a rapid and transient ER stress response, characterized by an initial increase in H2O2 and early expression of UPR-related genes, with a return to basal levels within 24 hours. Under salinity, plants previously treated with TM exhibited lower H2O2 accumulation, earlier and more efficient activation of pathways associated with ER signaling and sodium transport, as well as reduced expression of chaperones and Na+ transporters. Proteomic analysis revealed that salinity promoted broad metabolic repression, including reductions in enzymes of the Calvin cycle and glycolysis (GAPDH, triose phosphate isomerase) and in ribosomal proteins, whereas TM priming attenuated this suppression and promoted selective reinforcement of the translational machinery and proteins associated with stress adaptation. Metabolomic and lipidomic profiles indicated enhanced osmotic adjustment and membrane remodeling, reinforcing cellular stability under stress conditions. It is concluded that transient ER activation acts as a physiological preconditioning mechanism, coordinating redox regulation, proteostasis, ionic homeostasis, and metabolic reprogramming. These findings expand the understanding of the ER as a regulatory hub in plant adaptation to salt stress and highlight promising molecular

targets for breeding strategies aimed at increasing cowpea resilience in salinized environments.