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 cDNA clone encoding a novel Myb‐related protein, designated MybSt1, was isolated from a potato cDNA expression library by South Western screening using the CaMV 35S promoter domain A as a probe. Sequence comparison shows a small region with some homology to the highly conserved DNA binding domain of the c‐myb proto‐oncogene consisting of three imperfect repeats. The Myb motif of the MybSt1 protein is distinct from the plant Myb DNA binding domain described so far. In contrast to the known plant Myb proteins, with two repeats required for the DNA binding activity, the clone mybSt1 contains only one such repeat. Nevertheless, the Myb‐related protein MybSt1 is able to bind to DNA in a sequence‐specific manner. In addition to the Myb‐like region, the protein MybSt1 contains an acidic segment in its central region as well as a proline‐rich region near the C‐terminus. Applying the random binding site selection technique, high‐affinity DNA binding sites for MybSt1 were identified, sharing the core motif GGATA. In transient expression assays using plant protoplasts, clear evidence was obtained for this myb clone functioning as a transcriptional activator.

A cauliflower mosaic virus (CaMV) 35S promoter derivative, which is tightly repressed by the Tn 10 encoded Tet repressor in a transient expression system as well as in transgenic plants has been constructed. After treatment of transgenic plants with tetracycline (Tc) the activity of the reporter enzyme beta-glucuronidase (GUS) increased up to 500-fold in tissue culture as well as under greenhouse conditions. Efficient de-repression was achieved by Tc uptake through the roots as well as by Tc treatment of leaves of intact plants. As Tc is not very stable in the plants, this system can also be used for a transient expression of a transgene. This system provides a unique tool for regenerating transgenic plants carrying a repressed transgene and for efficiently de-repressing its activity by a specific inducer at any time point of further development.

SummaryStarch phosphorylation by glucan, water dikinase (GWD; EC 2.7.9.4) is an essential step in the breakdown of native starch particles, but the underlying mechanisms have remained obscure. In this paper, the initial reactions of starch degradation were analyzed using crystallized maltodextrins as model carbohydrates. As revealed by X-ray diffraction analysis, the crystallized maltodextrins represent the B-type starch allomorph. Recombinant GWD phosphorylated crystalline maltodextrins with a high specific activity (55-60 nmol mg )1 protein min )1 ), but exhibited very little activity with the same maltodextrins that had been solubilized by heat treatment. Recombinant phosphoglucan, water dikinase (PWD; EC 2.7.9.5) utilized the crystalline maltodextrins only when pre-phosphorylated by GWD. Phosphorylation of crystalline maltodextrins, as catalyzed by GWD, initiated solubilization of neutral as well as phosphorylated glucans. In both the insoluble and the soluble state, mono-, di-and triphosphorylated a-glucans were observed, with wide and overlapping ranges of degree of polymerization. Thus, the substrate specificity of the GWD is defined by the physical arrangement of a-glucans rather than by structural parameters, such as the distribution of branching points or degree of polymerization. Unlike GWD and PWD, recombinant b-amylase isozyme 3 (BAM3), which has been shown to be essential for plastidial starch degradation, preferentially degraded soluble maltodextrins rather than crystallized glucans. In summary, two conclusions were reached. Firstly, carbohydrate targets of GWD are primarily defined by the molecular order of glucan helices. Secondly, GWD-catalyzed phosphorylation mediates the phase transition of glucans from a highly ordered to a less ordered and hydrated state.

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