Role of T-region borders in Agrobacterium host range

The limited host range AB3 strain of Agrobacterium tumefaciens induces tumors by transferring two T-regions, TA and TB. TA is a deleted version of the well-known biotype I octopine TL-region that lacks the iaa and ipt genes, but carries an intact oncogene, gene 6b, and typical left and right border sequences. TB carries two iaa genes that together code for the synthesis of indoleacetic acid. Gene 6b and the iaa gene act synergistically when transferred in a coinoculation experiment. The TA-region of the limited host range isolate Ag57 is related to the TA-region of AB3, but differs from it at several positions. The most significant difference is the absence of the right border region. In spite of this, Ag57 and the exconjugant strain C58C9(pTiAg57) induce normal tumors on Nicotiana rustica and Vitis vinifera. Various experiments indicate that gene 6b of the Ag57 TA-region is active and transferred in spite of the absence of the right border. On N. tabacum, C58C9(pTiAg57) is nononcogenic but becomes oncogenic when the pTiAg57 TA-region is restored by the right TA border sequence of pTiAB3. Thus, the right TA border sequence of the biotype III limited host range strains is required for tumor induction on some hosts, but not on others.     

Sequence of the iaa and ipt region of different Agrobacterium tumefaciens biotype III octopine strains: reconstruction of octopine Ti plasmid evolution

The TA regions of biotype III octopine/cucumopine (OC) Ti plasmids are closely related to the TL region of the biotype I octopine Ti plasmids pTiAch5 and pTi15955. Sequence analysis shows that the limited and wide host range biotype III OC TA regions are derived from a common ancestor structure which lacked the 6a gene found in the biotype I octopine TL region. The TA region of the wide host range OC Ti plasmids has conserved most of the original TL-like structure. In most wide host range OC isolates the TA-iaaH gene is inactivated by the insertion of an IS866 element. However, the TA region of the wide host range isolate Hm1 carries an intact TA-iaaH gene. This gene encodes a biologically active product, as shown by root induction tests and indole-3-acetic acid measurements.The limited host range OC Ti plasmids pTiAB3 and pTiAg57 have shorter TA regions which are derived from a wide host range TA region. The AB3 type arose by an IS868-mediated, internal TA region deletion which removed the iaa genes and part of the ipt gene and left a copy of IS868 at the position of the deleted fragment. The pTiAB3 iaa/ipt deletion was followed by insertion of a second IS element, IS869, immediately 3 of the ipt gene. pTiAg57 underwent the same iaa-ipt deletion as pTiAB3, but lacks the IS868 and IS869 elements.Analysis of the various TA region structures provides a detailed insight into the evolution of the biotype III OC strains.     

Contractile eukaryotic flagella: Centrin is involved

Summary Isolated transverse flagella ofPeridinium inconspicuum (Dinophyceae) undergo a rapid Ca²⁺-induced (50M Ca²⁺) contraction in the absence of exogenous ATP. Longitudinal flagella from the same species do not contract under these conditions. Contraction leads to a supercoiling of the axoneme and a shortening of the paraxonemal fiber that accompanies the axoneme over most of its length. Using a polyclonal antibody generated against centrin, a 20 kDa Ca²⁺-modulated contractile protein of striated flagellar roots of the green flagellateTetraselmis striata, we have found that the paraxonemal fiber in transverse flagella of three taxa ofDinophyceae is immunoreactive by indirect immunofluorescence. The localization of the antigen in the paraxonemal fiber of transverse flagella was confirmed by two-colour double immunofluorescence using monoclonal mouse-anti--tubulin for identification of the axoneme. No structure was immunoreactive to anticentrin in the longitudinal flagella of all taxa. Electrophoretic and immunoblot analysis of isolated flagella ofP. inconspicuum show that the antigen is a 21 kDa protein, indicating that it is either centrin or a closely related protein. We conclude that centrin confers contractility to the transverse flagellum of dinoflagellates and possibly to other contractile eukaryotic flagella.Abbreviations ASP-H artificial seawater medium with Hepes-buffer - BSA bovine serum albumine - DTT dithiothreitol - EGTA ethylene glycol bis(2-amino-ethylether)tetraacetic acid - FITC fluorescein isothiocyanate - MT buffer microtubule stabilizing buffer - PBS phosphate buffered saline - SDS sodium dodecyl sulfate - TLCK N-p-tosyl-l-lysine chloromethyl ketone - TRITC tetramethylrhodamine isothiocyanate     

Sequence and distribution of IS866, a novel T region-associated insertion sequence from Agrobacterium tumefaciens

We have identified a new insertion sequence, IS866, located in the auxin synthesis gene TA iaaH of Tm4, a wide host range biotype III octopine/cucumopine type Agrobacterium tumefaciens strain with two T regions on its tumor-inducing (Ti) plasmid, TA, and TB. IS866 is 2716 bp long, has inverted repeats of 27 bp with three mismatches, and generates 8-bp direct repeats upon integration. In addition to IS866, pTiTm4 carries two copies of a related element, IS867, associated with TA and TB, respectively. A systematic study of 92 virulent Agrobacterium strains has shown that among the three biotypes all octopine/cucumopine and vitopine biotype III isolates contain IS866-like elements. The various octopine/cucumopine Ti plasmids always carry IS866 and IS867 at the same position as in pTiTm4. The chromosomes of the bacteria which contain these Ti plasmids also carry IS866 and IS867 copies but in varying numbers and locations.     

The reduction state of the Q-pool regulates the electron flux through the branched respiratory network of Paracoccus denitrificans.

In this work we demonstrate how the reduction state of the Q-pool determines the distribution of electron flow over the two quinol-oxidising branches in Paracoccus denitrificans: one to quinol oxidase, the other via the cytochrome bc1 complex to the cytochrome c oxidases. The dependence of the electron-flow rate to oxygen on the fraction of quinol in the Q-pool was determined in membrane fractions and in intact cells of the wild-type strain, a bc1-negative mutant and a quinol oxidase-negative mutant. Membrane fractions of the bc1-negative mutant consumed oxygen at significant rates only at much higher extents of Q reduction than did the wild-type strain or the quinol oxidase-negative mutant. In the membrane fractions, dependence on the Q redox state was exceptionally strong corresponding to elasticity coefficients close to 2 or higher. In intact cells, the dependence was weaker. In uncoupled cells the dependence of the oxygen-consumption rates on the fractions of quinol in the Q-pool in the wild-type strain and in the two mutants came closer to that found for the membrane fractions. We also determined the dependence for membrane fractions of the wild-type in the absence and presence of antimycin A, an inhibitor of the bc1 complex. The dependence in the presence of antimycin A resembled that of the bc1-negative mutant. These results indicate that electron-flow distribution between the two quinol-oxidising branches in P. denitrificans is not only determined by regulated gene expression but also, and to a larger extent, by the reduction state of the Q-pool.     

Investigations into rabies II

Antonie van Leeuwenhoek -     

Autosomal-dominant isolated growth hormone deficiency (IGHD type II) with normal GH-1 gene

BACKGROUND: Autosomal-dominant isolated GH deficiency (IGHD) is a rare disorder that is commonly believed to be due to heterozygous mutations in the GH-1 gene (GH-1). These mutations cause the production of a protein that affects the release of the product of the normal allele. Rarely, heterozygous mutations in the gene encoding for HESX-1 gene (HESX-1) may cause autosomal-dominant IGHD, with penetrance that has been shown to be variable in both humans and mice. SUBJECTS AND METHODS: We have sequenced the whole GH-1 in the index cases of 30 families with autosomal-dominant IGHD. In all the families other possible causes of GH deficiency and other pituitary hormones deficits were excluded. We here describe the clinical, biochemical and radiological picture of the families without GH-1 mutations. In these families, we also sequenced the HESX-1. RESULTS: The index cases of the five families with autosomal-dominant IGHD had normal GH-1, including the intronic sequences. They had no HESX-1 mutations. CONCLUSION: This study shows that GH-1 mutations are absent in 5/30 (16.6%) of the families with autosomal-dominant IGHD and raises the possibility that mutations in other gene(s) may be involved in IGHD with this mode of transmission.     

Development and evaluation of a vaginal ring device for sustained delivery of HIV microbicides to non-human primates

Background  There is considerable interest in developing coitally independent, sustained release formulations for long-term administration of HIV microbicides. Vaginal ring devices are at the forefront of this formulation strategy.
Methods  Non-medicated silicone elastomer vaginal rings were prepared having a range of appropriate dimensions for testing vaginal fit in pig-tailed and Chinese rhesus macaques. Cervicovaginal proinflammatory markers were evaluated. Compression testing was performed to compare the relative flexibility of various macaque and commercial human rings.
Results  All rings remained in place during the study period and no tissue irritation or significant induction of cervicovaginal proinflammatory markers or signs of physical discomfort were observed during the 8-week study period.
Conclusions  Qualitative evaluation suggests that the 25 × 5-mm ring provided optimal fit in both macaque species. Based on the results presented here, low-consistency silicone elastomers do not cause irritation in macaques and are proposed as suitable materials for the manufacture of microbicide-loaded vaginal rings.