Insights into sucrose pathway of chicory stems by integrative transcriptomic and metabolic analyses

The worldwide-cultivated chicory (Cichorium intybus L.) produces food and beneficial compounds, and young pre-flowering inflorescence stems are newly marketed vegetables. These sink-organs undergo growth by metabolizing sugars of leaf origin; the carbohydrate content and sweetness are crucial aspects for consumers’ nutrition and acceptance. NMR profiling of 31 hydrosoluble phytochemicals showed that stem contents varied as influenced by genotype, environment and interaction, and that higher sucrose levels were associated with the sweeter of two landraces. Integrative analyses of metabolic and transcriptomic profile variations allowed the dissection of sucrose pathway. Overall, 427 and 23 unigenes respectively fell into the categories of sucrose metabolism and sugar carriers. Among 10 differentially expressed genes, the 11474/sucrose synthase, 53458/fructokinase, 9306 and 17035/hexokinases, and 20171/SWEET-type genes significantly associated to sugar content variation, and deduced proteins were characterised in silico. Correlation analyses encompassing sugar level variation, expressions of the former genes and of computationally assigned transcription factors (10938/NAC, 14712/bHLH, 40133/TALE and 17846/MIKC) revealed a gene network. The latter was minimally affected by the environment and accomplished with markers, representing a resource for biological studies and breeding. Integrative analysis combining metabolic and gene transcription profiles were used to give insights into chicory stem sugar metabolism of two landraces grown in different sites in order to define a gene network subtending sugar content differences. [Display omitted] •Sugar sink of stems was studied in chicories diverging for sugar content.•Sucrose level and sweetness were affected by the genotype, site and interactions.•Catabolism/transport gene expression variations associated to sucrose differences.•Transcription factors were in silico assigned to build a gene-metabolite network.•The network was unaffected by the environment and provided gene markers.