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Differential gene expression in Roseburia inulinivorans grown on inulin and starch

ABSTRACT: Roseburia inulinivorans is a recently identified motile representative of the Firmicutes that contributes to butyrate formation from a variety of dietary polysaccharide substrates in the human large intestine. Microarray analysis was used here to investigate substrate-driven gene expression changes in R. inulinivorans A2-194. A cluster of fructo-oligosaccharide (FOS)/inulin utilisation genes induced during growth on inulin included one encoding a b-fructofuranosidase protein that was prominent in the proteome of inulin-grown cells. This cluster also included a 6-phosphofructokinase and an ABC transport system, while a distinct inulin-induced 1-phosphofructokinase was linked to a fructose-specific phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS II transport enzyme). Real-time PCR analysis demonstrated that the b-fructofuranosidase and adjacent ABC transport protein showed greatest induction during growth on inulin, whereas the 1-phosphofructokinase enzyme and linked PTS II transport system were most strongly up-regulated during growth on fructose, indicating that these two clusters play distinct roles in the utilization of inulin. The R. inulinivorans B-fructofuranosidase was over-expressed in E. coli and shown to hydrolyse fructans ranging from inulin down to sucrose, with greatest activity on fructo-oligosacharides. Genes induced on starch included the major extra-cellular a-amylase and two distinct a-glucanotransferases together with a gene encoding a flagellin protein. The latter response may be concerned with improving bacterial access to insoluble starch particles.

ORGANISM(S): Roseburia inulinivorans DSM 16841 Roseburia inulinivorans

PROVIDER: GSE22245 | GEO | 2010/07/24

SECONDARY ACCESSION(S): PRJNA128757

REPOSITORIES: GEO

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Project description:Roseburia inulinivorans is a recently identified motile representative of the Firmicutes that contributes to butyrate formation from a variety of dietary polysaccharide substrates in the human large intestine. Microarray analysis was used here to investigate substrate-driven gene expression changes in R. inulinivorans A2-194. A cluster of fructo-oligosaccharide (FOS)/inulin utilisation genes induced during growth on inulin included one encoding a b-fructofuranosidase protein that was prominent in the proteome of inulin-grown cells. This cluster also included a 6-phosphofructokinase and an ABC transport system, while a distinct inulin-induced 1-phosphofructokinase was linked to a fructose-specific phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS II transport enzyme). Real-time PCR analysis demonstrated that the b-fructofuranosidase and adjacent ABC transport protein showed greatest induction during growth on inulin, whereas the 1-phosphofructokinase enzyme and linked PTS II transport system were most strongly up-regulated during growth on fructose, indicating that these two clusters play distinct roles in the utilization of inulin. The R. inulinivorans B-fructofuranosidase was over-expressed in E. coli and shown to hydrolyse fructans ranging from inulin down to sucrose, with greatest activity on fructo-oligosacharides. Genes induced on starch included the major extra-cellular a-amylase and two distinct a-glucanotransferases together with a gene encoding a flagellin protein. The latter response may be concerned with improving bacterial access to insoluble starch particles. RNA was purified from mid-exponential phase (OD650 = 0.4) cultures of R. inulinivorans grown on basal YCFA supplemented with a single substrate of either starch or inulin using the RNeasy RNA purification kit (Qiagen), and the mRNA component enriched using the MICROBExpress system (Ambion). The purified RNA (1 ug) was labelled by reverse transcription (Amersham), employing random nonamer extension incorporating either dCTP-Cy3 or dCTP-Cy5 dyes. In order to ensure reproducibility, and to obtain statistically significant results, the dye labelling was swapped for a second hybridisation. RNA purified from a separate biological replicate was labelled and hybridised twice in the same way.

Project description:Helianthus tuberosus L., known as the Jerusalem Artichoke, is a hexaploid plant species, adapted to low nutrient soils, that accumulates high levels of inulin in its tubers. Inulin is a fructose-based polysaccharide used either as dietary fiber or for the production of bioethanol. Key enzymes involved in inulin biosynthesis are well known. However, the gene networks underpinning tuber development and inulin accumulation in H. tuberous remain elusive. To fill this gap, we selected 6,365 ESTs from a H. tuberosus library to set up a microarray platform and record their expression across three tuber developmental stages, when rhizomes start enlarging (T0), at maximum tuber elongation rate (T3) and at tuber physiological maturity (Tm), in “VR” and “K8-HS142”clones. The former was selected as an early tuberizing, the latter as a late-tuberizing clone. We quantified inulin and starch levels, and q-RT PCR confirmed the expression of key genes accounting for inulin biosynthesis. The microarray analysis revealed that the differences in morphological and physiological traits between tubers of the two clones are genetically determined since T0 and that is relatively low the number of differentially expressed ESTs across the stages shared between the clones (93). The expression of ESTs for sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 1-fructosyltransferase (1-FFT), the two critical genes for fructans polymerization, resulted to be temporarily synchronized and mirror the progress of inulin accumulation and stretching. The expression of ESTs for starch biosynthesis was insignificant throughout the developmental stages of the clones in line with the negligible level of starch into their mature tubers, where inulin was the dominant polysaccharide. Overall, our study disclosed candidate genes underpinning the development and storage of carbohydrates in the tubers of two H. tuberosus clones. A model according to which the steady state levels of 1-SST and 1-FFT transcripts are developmentally controlled and might represent a limiting factor for inulin accumulation has been provided. Our finding may have significant repercussions for breeding clones with improved levels of inulin for food and chemical industry.

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Differential gene expression in Roseburia inulinivorans grown on inulin and starch

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