There is growing interest in the use of inulins as substrates for the selective growth of beneficial gut bacteria such as bifidobacteria and lactobacilli because recent studies have established that their prebiotic effect is linked to several health benefits. In the present study, the impact of a verylong-chain inulin (VLCI), derived from globe artichoke (Cynara scolymus), on the human intestinal microbiota compared with maltodextrin was determined. A double-blind, cross-over study was carried out in thirty-two healthy adults who were randomised into two groups and consumed 10 g/d of either VLCI or maltodextrin, for two 3-week study periods, separated by a 3-week washout period. Numbers of faecal bifidobacteria and lactobacilli were significantly higher upon VLCI ingestion compared with the placebo. Additionally, levels of Atopobium group significantly increased, while Bacteroides -Prevotella numbers were significantly reduced. No significant changes in faecal SCFA concentrations were observed. There were no adverse gastrointestinal symptoms apart from a significant increase in mild and moderate bloating upon VLCI ingestion. These observations were also confirmed by in vitro gas production measurements. In conclusion, daily consumption of VLCI extracted from globe artichoke exerted a pronounced prebiotic effect on the human faecal microbiota composition and was well tolerated by all volunteers.Prebiotics: Bifidogenic effect: Gas production: Intestinal microfloraIn the last decade functional foods in human and animal nutrition have gained in importance. Within this field of research, scientific concepts underpinning directed modulation of the human gut microbiota towards a more beneficial composition have been developed (1,2) . The prebiotic approach advocates targeting selected indigenous beneficial bacteria through non-viable food ingredients (3) . The concept was recently updated by Gibson et al. (4) , and the weight of evidence for established and emerging prebiotics reviewed (5) . Much of the interest in the development of prebiotics aims at non-digestible oligosaccharides. These are short-chain carbohydrates that consist of two to twenty saccharide units. Examples include inulin-type fructans, galacto-oligosaccharides, isomaltooligosaccharides, xylo-oligosaccharides, soya-oligosaccharides, gluco-oligosaccharides and lacto-sucrose (6,7) , although each of these varies in their prebiotic potential.Inulin and fructo-oligosaccharides are plant b (2-1) fructans with a degree of polymerisation (DP) ranging from 2 to 60 or more for inulin, or from 2 to 10 for oligofructose (8) .There is a high degree of variability in DP distribution among products derived from different plant origins. Inulin derived from globe artichoke (Cynara scolymus) generally has the highest DP (9) whereas onion, garlic, Jerusalem artichoke (Heliantus tuberosus), leeks, asparagus and banana have lower DP (8) . The inulin content of Jerusalem artichoke ranges from 17 to 20·5 % on a fresh weight basis. Praznik et al. (10) found that 74 % ...

A chimaeric antisense construct was used to reduce the activities of the two major starch-synthase isoforms in potato tubers simultaneously. A range of reductions in total starch-synthase activities were found in the resulting transgenic plants, up to a maximum of 90% inhibition. The reduction in starch-synthase activity had a profound effect on the starch granules, which became extremely distorted in appearance compared with the control lines. Analysis of the starch indicated that the amounts produced in the tubers, and the amylose content of the starch, were not affected by the reduction in activity. In order to understand why the starch granules were distorted, amylopectin was isolated and the constituent chain lengths analysed. This indicated that the amylopectin was very different to that of the control. It contained more chains of fewer than 15 glucose units in length, and fewer of between 15 and 80 glucose units. In addition, the amylopectin contained more very long chains. Amylopectin from plants repressed in just one of the activities of the two starch-synthase isoforms, which we have reported upon previously, were also analysed. Using a technique different to that used previously we show that both isoforms also affect the amylopectin, but in a way that is different to when both isoforms are repressed together.

The tricarboxylic acid (TCA) cycle constitutes a major component of the mitochondrial metabolism of eucaryotes, including higher plants. To analyze the importance of this pathway, we down‐regulated mitochondrial citrate synthase (mCS; EC 4.1.3.7), the first enzyme of the TCA cycle, in transgenic potato plants using an antisense RNA approach. Several transformants were identified with reduced citrate synthase activity (down to approximately 6% of wild‐type activity). These plants were indistinguishable from wild‐type plants in the greenhouse during vegetative growth. A major change, however, was seen upon initiation of the generative phase (flower formation). In the case of transgenic plants with a strong reduction in citrate synthase activity (< 30% of wild‐type levels), flower buds formed > 2 weeks later as compared with wild‐type plants. Furthermore, flower buds from these plants did not develop into mature flowers but rather were aborted at an early stage of development. Microscopic analysis showed that in these cases ovaries disintegrated during flower development. We conclude that the TCA cycle is of major importance during the transition from the vegetative to the generative phase.

We have generated transgenic potato plants (Solanum fuberosum) containing the potato phytochrome protein encoded by the PHYA gene cDNA (phyA) in sense or antisense orientation under the control of the 35s cauliflower mosaic virus promoter. Plants with increased and decreased phyA levels were analyzed. When grown under white light, development and growth of sprouts and plants were barely distinguishable from wild type. Under continuous far-red light, stem extension, leaf expansion, and hook opening of sprouts were accelerated in phyA overexpressors and delayed in antisense plants. Sprouts with reduced phyA levels were less sensitive to red light with regard to stem extension and expression of the small subunit genes for ribulose bisphosphate carboxylase. Under low red 1ight:far-red light ratios, increased phyA levels reduced the stem extension component of the shade-avoidance response, whereas decreased levels led to an increase in the response.

Mitochondrial citrate synthase (EC 4.1.3.7) represents the first enzyme of the tricarboxylic acid cycle, catalyzing the condensation of acetyl-CoA and oxaloacetate, finally yielding citrate and CoA. We report here the isolation of cDNA clones encoding citrate synthase from Nicotiana tabacum, Beta vulgaris and Populus. Nucleotide and deduced amino acid sequences were compared with previously published sequences of mitochondrial citrate synthases from Arabidopsis thaliana and potato, as well as with the sequence of glyoxysomal citrate synthase from pumpkin. Homologies between the various plant mitochondrial enzymes were in the range from 77.2% (potato vs. Arabidopsis) to 94.2% (potato vs. tobacco) on the nucleotide level (coding regions only), and in the range from 70.1% to 90.4% (potato vs. Arabidopsis, and potato vs. tobacco, respectively) on the amino acid level. Identities of the mitochondrial isozymes to the pumpkin glyoxysomal enzyme were below 30% on the nucleotide and amino acid level. In Northern blot experiments citrate synthase mRNA was detected in all tissues analyzed. However, levels of expression showed tissue dependency despite the fact that citrate synthase is usually considered a house-keeping enzyme. Whether these different levels of expression reflect tissue-specific variations with respect to basic metabolism awaits further analysis.