Efeito do pré-tratamento foliar com H2O2 sobre o proteoma e enzimas antioxidantes em plantas de feijão-de-corda submetidas ao estresse salino

Abstract

The cowpea [Vigna unguiculata (L.) Walp.] has a great nutritional an socioeconomic importance in Brazil. However, in the Northeastern there is a decline in its agricultural production, which might be associated with an increased salinity in the soil. It is know that salinity causes metabolic changes, accelerating the production of reactive oxygen species (ROS). They lead to several damage in cells, but also play a crucial role as signaling molecules for acclimation to various abiotic stresses. For this reason, the aim of this work was to evaluate the effects of hydrogen peroxide (H2O2) leaf pretreatment in cowpea plants on acclimation to salt stress, studying the physiological, biochemical and molecular mechanisms. Therefore, two experiments were conducted in a greenhouse under hydroponic conditions, using the cowpea, cultivar TVu 2331. In the first experiment, were evaluated physiological change induced by H2O2 leaf spraying pretreatment in different concentrations (1, 5, 10, 25, 50 e 100 mM), in cowpea plants subjected to salt treatment (NaCl 80 mM). The results showed that the spraying with 25 mM H2O2 solution was able to alleviate the deleterious effects of salinity on growth. From this point, in the second experiment, were evaluated the effects of this concentration of H2O2 leaf pretreatment on the biochemical and proteomic changes in plants during saline treatment. It was found the involvement of enzymes SOD and CAT in the initial times after spraying of H2O2, indicating an antioxidant response. However, in the presence of NaCl, the lipid peroxidation was not reduced by H2O2 spraying. In the proteomic study it was verified that pretreated with water and salt treatment altered the expression of 38 proteins, as H2O2 pretreatment and saline treatment were able to alter expression of 28 proteins and pretreatment with H2O2 was only able to change expression 11 proteins. Among these proteins, 44 of them had their identity determined by mass spectrometry (ESI-Q-TOF). Most of the identified proteins in the treatments performed were related to the photosynthetic process, to protection / defense and to carbohydrate metabolism. However, in the saline treatment revealed a decrease in the expression the proteins related to photosynthesis, it was observed that the pretreatment with H2O2 was able to enhance the expressed proteins, such as Rubisco and protein related to oxygen evolution (OEE2). In addition, that treatment displayed the largest number of proteins associated with protection/defense, such as glutathione reductase, chloroplast chaperonin, cytosolic APX and POB1 BTB/POZ. These data should contribute to a better understanding of the biochemical and molecular mechanisms of cowpea, TVu cultivar, involved in acclimation to salt stress previously treated with H2O2. The acquired knowledge generates perspectives for the development of biotechnological strategies in order to obtain cultivars that are more tolerant to salinity.