Aplicação da técnica DESI-MSI em metabolômica vegetal: estudos de fisiologia e farmacognosia e detecção de transgenia

Abstract

The ambient ionization technique known as DESI (Desorption Electrospray Ionization) has been used in mass spectrometry to allow the analysis of samples in their natural environment with no need of using laborious sample pre-treatment procedures. When coupledto a mobile platform, chemical images of a sample can be obtained in a methodology known as DESI-MSI (Desorption Electrospray Ionization Mass Spectrometry Imaging). In this work, chemical images of 13 metabolites of transport and storage (carbohydrates, amino acids and ureides) were obtained in leaves of peppermint (Mentha × piperita L.) of different maturation stages (young, intermediate and mature), making a comparison among the spatial distribution of these metabolites in these leaf types. It was also possible to evaluate the spatial distribution of 21 among the major flavonoids in mature leaves of this species using DESI-MSI and DI-ESI-MS (Direct Infusion Electrospray Ionization Mass Spectrometry). The DESI-MSI technique was also used to detect metabolic differences between transgenic and conventional plants. For this, chemical images of leaves and grains of transgenic and conventional soybean were obtained. Seven (7) diagnostic metabolites were selected for the differentiation between these types of samples. In an analogous study, remarkable differences between the chemical images of 12 metabolites observed in transgenic and conventional corn grains were noticed. In a parallel investigation, DI-ESI-MS was used toevaluate the metabolic changes that occur, as a function of time, in transgenic and conventional soybean leaves submitted to the glyphosate herbicide. In this study, it was selected shikimic acid (mainly) and 12 other metabolites that presented different behavior in the transgenic andconventional samples. The results presented in this work are unprecedented, in which relevant information was achieved, maily, from the DESI-MSI and, to a lesser extent, DI-ESI-MS analysis. It is amultidisciplinary work that opens a range of immense possibilities for the application of these techniques in other studies of vegetal metabolomics.