Uso de priming com tunicamicina e hidropriming em sementes de arroz como estratégia para mitigar efeitos do estresse salino

Abstract

Food insecurity is a problem that intensifies with the growing increase in population. In addition, biotic and abiotic stresses affect plant growth and, consequently, productivity. To address this issue, studies suggest that the use of priming – a technique that involves soaking seeds in chemical compounds before sowing to induce responses that improve plant adaptation – is able to develop tolerance against a range of stresses such as drought and salinity. One of the stress response pathways is the Unfolded Protein Response (UPR), which occurs in the endoplasmic reticulum (ER) and is triggered by the accumulation of misfolded proteins, leading to the production of chaperones that alleviate the stress. The use of chemical inducers like tunicamycin (TM) has proven to be a strategy to stimulate the ER response by inducing higher expression of genes related to this organelle and consequently reducing stress. Therefore, this study aims to test the hypothesis that TM priming in rice seeds induces tolerance in plants subjected to 60 mM NaCl, similarly to hydropriming. Rice seeds were primed with tunicamycin and ultrapure water and sown in vermiculite. Seventeen days after sowing, the plants were transferred to a hydroponic system and subjected to 60 mM NaCl for 14 days, then collected. Salinity significantly reduced fresh and dry weight, stomatal conductance, potassium concentration in both shoots and roots and promoted higher sodium accumulation. However, TM priming induced an increase in root fresh and dry weight under saline conditions, and both treatments reduced sodium accumulation in roots under the same condition. Furthermore, the priming treatments maintained the levels of photosynthetic pigments and carbon assimilation rates between 0 and 60 mM NaCl. Salinity was the main factor separating metabolic profiles. Proline, valine, pyroglutamic acid, and glutamic acid were identified as common metabolites for the treatments under 60 mM NaCl, while threonine, leucine, and lactitol were specific to the control, hydropriming, and TM treatments, respectively, molecules that are osmotically active and involved in plant antioxidant pathways. Thus, it is suggested that TM priming has the potential to alleviate the detrimental effects of salinity on rice, but further analysis is needed to clarify the mechanisms through which priming affects the plant’s physiological responses.