Desenvolvimento de substrato e adequação de metodologia para detecção de β-1,3 glucanase em soja Glycine max (L.) Merril

Abstract

The current food production model based on the use of chemical pesticides, has been discussed and questioned, considering the risks to the environment and food security. Many efforts have been made for alternative methods to be used in disease control, such as using resistance inductors. The inducers (elicitors) that may be biotic or abiotic, inorganic, organic or synthetic nature, are capable of inducing a defense response when they bind to receptors of the plasma membrane of the plant cell. They can induce systemic acquired resistance (SAR), which is one of the most important forms of resistance, because it confers systemic protection to the plant to a broad spectrum of microorganisms. Among the defense mechanisms of SAR, are the cell wall modifications, the production of phytoalexins, and concomitantly increased expression of pathogenesis related genes, which express the pathogenicity-related proteins (PR proteins). Among the PR proteins, the most important are the chitinase (PR-3) and β-1,3 glucanases (PR-2), which have hydrolytic activity, often synergistic, cleaving structural chitin and glucan polymers, respectively, present in the wall of pathogens, especially fungi. The activity of these enzymes is enhanced when plants are treated with specific inducers or when attacked by their natural enemies. However, research of new inductors require a series of tests to effective proof that plant defense response has been activated. Biochemical analysis of PR-proteins, such as β-1,3-glucanase, are needed to support the discovery of new and efficient inductors. However, the current enzyme substrate available in the market to evaluate this enzyme has shown discontinuous production. In this scenario, this study aimed to develop substrate and matching methodology for detecting β-1,3 glucanase in soybean plants - Glycine max (L.) Merr, main culture produced in Brazil. It has been developed two substrates glucan base: Curdlan-RBB and Scleroglucan-RBB. The efficiency of the substrates was compared with other currently available methods of determination, and the substrates were tested produced through β-1,3 glucanase purified action. Since the tests were positive biochemical analysis was performed with induced systemically and soybean plants inoculated with Phakopsora pachyrhizi fungus Syd. & P. Syd. The results showed that all substrates enables to quantify the enzymatic activity of β-1,3 glucanase, hence one of the substrates developed in this research, the scleroglucan-RBB had higher efficiency to commercial substrate AZCLCurdlan®.