Alterações no fluxo metabólico em folhas de duas cultivares de feijão-caupi sob infecção do vírus CPSMV

Abstract

Cowpea (Vigna unguiculata (L.) Walp) is a species of paramount importance for the Northeast region of Brazil, being responsible for more than one million hectares of cultivated land every year in the region. The genetic diversity of cowpea allows genotypes to present substantial differences in terms of yield and performance against biotic and abiotic stresses. In this context, infection by the severe cowpea mosaic virus (CPSMV) is responsible for considerable losses in production. Thus, it is important to investigate the mechanisms underlying resistance and sensitivity to CPSMV to better understand which factors regulate the dichotomy between growth and defense to CPSMV in this species. In this study, two cultivars with contrasting characteristics were used; (i) macaibo - resistant to abiotic (e.g. heat and water scarcity) and biotic (e.g. viral infections) stresses, but with low productivity; (ii) pitiuba - sensitive to viral infection as well as to abiotic factors, but with greater productive capacity. To unravel the metabolic responses of macaibo and pitiuba to infection by CPSMV, plants of these genotypes were cultured and, after reaching stage V3, the central leaf of the second trifoliate, here called the local leaf, was inoculated with the virus. The trifoliate was collected and immersed in glucose solution uniformly labeled with carbon 13 (glucose-¹³C), being removed and frozen in 2 and 8 hours after inoculation of the virus. Polar metabolites were extracted and analyzed via gas chromatography coupled to a mass spectrometer. The metabolites were identified based on libraries, then statistical treatment was performed to calculate the relative enrichment of ¹³C (R¹³C) in the identified fragments. An increase in R¹³C was identified in myo-inositol, butyric acid, glucose and sucrose in macaibo. In Pitiuba, an increase in R¹³C was found only in sucrose. However, increases in ¹³C were observed in some isotopologes of other metabolites in both genotypes. The stress response of Macaibo is potentially broader than that of Pitiuba, modifying different pathways, which may explain its better resistance to stresses, however, conclusions about the different metabolic responses of genotypes to CPSMV infection are still limited.