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Effects of Different Carbohydrate Sources on Fructan Metabolism in Plants of Chrysolaena obovata Grown in vitro


Chrysolaena obovata (Less.) Dematt., previously named Vernonia herbacea, is anAsteraceae native to the Cerrado which accumulates about 80% of the rhizophoredry mass as inulin-type fructans. Considering its high inulin production and the wideQ1 Q2application of fructans, a protocol for C. obovata in vitro culture was recently established.Q8Carbohydrates are essential for in vitro growth and development of plants and can alsoact as signaling molecules involved in cellular adjustments and metabolic regulation.This work aimed to evaluate the effect of different sources of carbohydrate on fructanmetabolism in plants grown in vitro. For this purpose, C. obovata plants cultivated in vitrowere submitted to carbon deprivation and transferred to MS medium supplementedwith sucrose, glucose or fructose. Following, their fructan composition and activity andexpression of genes encoding enzymes for fructan synthesis (1-SST and 1-FFT) anddegradation (1-FEH) were evaluated. For qRT-PCR analysis partial cDNA sequencescorresponding to two different C. obovata genes, 1-SST and 1-FFT, were isolated. As expected,C. obovata sequences showed highest sequence identity to other Asteraceae 1-SSTand 1-FFT, than to Poaceae related proteins. A carbon deficit treatment stimulatedthe transcription of the gene 1-FEH and inhibited 1-SST and 1-FFT and carbohydratesupplementation promoted reversal of the expression profile of these genes. With theexception of 1-FFT, a positive correlation between enzyme activity and gene expressionwas observed. The overall results indicate that sucrose, fructose and glucose act similarlyon fructanmetabolismand that 1-FEH and 1-SST are transcriptionally regulated by sugarin this species. Cultivation of plants in increasing sucrose concentrations stimulatedsynthesis and inhibited fructan mobilization, and induced a distinct pattern of enzymeactivity for 1-SST and 1-FFT, indicating the existence of a mechanism for differentialregulation between them. (AU)

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