Papel funcional da família de enzimas glicolato oxidase (GOX) e catalase (CAT) em feijão-caupi (Vigna unguiculata [L.] Walp.) na resposta ao Cowpea Severe Mosaic Virus

Abstract

With the increase in food shortages and nutritional deficiencies, the choice of alternative crops with relevant characteristics is important. Vigna unguiculata L. is therefore a crop of great interest. However, cowpeas are still susceptible to some pathogens, such as the CowPea Severe Mosaic Virus (CPSMV). Under adverse conditions, such as infection by pathogens, one of the initial mechanisms for the stress response involves the production of reactive oxygen species. One of these molecules is hydrogen peroxide, which has its highest production rate related to Glycolate Oxidase (GOX), an enzyme in the photorespiration process, but like all reactive species, its production and consumption must be finely balanced, so there is the peroxisomal enzyme Catalase (CAT), responsible for this control during a stress phenomenon. The aim of this study was therefore to analyse the expression of GOX and CAT gene copies, at transcript and activity level, in response to CPSMV. To this end, the plant specimens were inoculated with CPSMV at three time points (16 hours, 48 hours and 144 hours). Analyses of catalase enzyme activity showed differences between the cultivars only in the initial hours (16h), in the control conditions of inoculated Pitiúba and Mock, possibly related to the initial response to the pathogen. In addition, analyses using DAB (3,3'-Diaminobenzidine) staining, MDA (Malonaldehyde) and peroxide content were used to determine the degree of oxidative stress, again with differences only between Pitiúba Mock and inoculated at 16 and 48 hours. In addition, the expression data showed differences mainly in the VuGOX1 gene in the Macaíbo cultivar, whose expression was induced during infection compared to the Mock. While VuGOX2 was the gene with the highest abundance at transcript level, showing differences between the cultivars at times of 16 and 144h, with reduced expression in inoculated Pitiúba compared to Mock 144h. Analysis of cis-elements showed regions that corroborate points raised in the discussion, mainly related to the pathogen response route and the synthesis of salicylic acid (SA). Thus, it is hoped that the results found will help breeding programmes and understanding of the resistance phenomenon.