Hardening by abscisic acid of tobacco plantlets grownin vitro

Tobacco plantlets were grownin vitro on Murashige and Skoog’s medium with2 % of saccharose. Addition of 0.01 mM abscisic acid (ABA) into the medium decreased stomatal conductance of the adaxial epidermis and especially the abaxial epidermis without negative effects on growth parameters. As a result the rate of water loss from ABA-treated plantlets taken out of cultivation vessels was slower than that of control plantlets. This could help their acclimation after transplantation toex vitro conditions.     

ONTOGENETIC NICHE SHIFT IN THE BRACHIOPOD TEREBRATALIA TRANSVERSA: RELATIONSHIP BETWEEN THE LOSS OF ROTATION ABILITY AND ALLOMETRIC GROWTH

Abstract: Many articulated brachiopods experience marked life habit variations during ontogeny because they experience their fluid environment at successively higher Reynolds numbers, and they can change the configuration of their inhalant and exhalant flows as body size increases. We show that the extant brachiopod Terebratalia transversa undergoes a substantial ontogenetic change in reorientation governed by rotation around the pedicle. T. transversa′s reorientation angle (maximum ability to rotate on the pedicle) decreases during ontogeny, from 180 degrees in juveniles to 10–20 degrees in individuals exceeding 5 mm, to complete cessation of rotation in individuals larger than 10 mm. Rotation ability is substantially reduced after T. transversa achieves the adult lophophore configuration and preferred orientation with respect to ambient water currents at a length of 2.5–5 mm. We hypothesize that the rotation angle of T. transversa is determined mainly by the position of ventral and dorsal points of attachment of dorsal pedicle muscles relative to the pedicle. T. transversa shows a close correlation between the ontogenetic change in reorientation angle and ontogeny of morphological traits that are related to points of attachment of dorsal pedicle muscles, although other morphological features can also limit rotation in the adult stage. The major morphological change in cardinalia shape and the observed reduction of rotation affect individuals 2.5–10 mm in length. The position of ventral insertions of dorsal pedicle muscles remains constant, but contraction of dorsal pedicle muscles is functionally handicapped because dorsal insertions shift away from the valve midline, rise above the dorsal valve floor, and become limited by a wide cardinal process early in ontogeny (<5 mm). The rate of increase of cardinal process width and of distance between dorsal pedicle muscle scars substantially decreases in the subadult stage (5–10 mm), and most of the cardinalia shell traits grow nearly isometrically in the adult stage (>10 mm). T. transversa attains smaller shell length in crevices than on exposed substrates. The proportion of small‐sized individuals and population density is lower on exposed substrates than in crevices, indicating higher juvenile mortality on substrates prone to grazing and physical disturbance. The loss of reorientation ability can be a consequence of morphological changes that strengthen substrate attachment and maximize protection against biotic or physical disturbance (1) by minimizing torques around the pedicle axis and/or (2) by shifting energy investments into attachment strength at the expense of the cost involved in reorientation.     

Prevalence of the Helicobacter pylori babA2 gene and correlation with the degree of gastritis in infected Slovenian children

The aims of our study were to determine the prevalence of the babA2 gene within Helicobacter pylori strains circulating in the Slovenian pediatric population, to further clarify its significance in causing inflammation of gastric mucosa in children and to verify whether cagA, vacA, iceA and babA genes work independently or synergistically in causing gastritis. A total of 163 H. pylori isolates obtained from the same number of children were tested for the presence of cagA, vacA and iceA genes using previously established methods, while the babA2 gene was determined using novel polymerase chain reaction assay targeting a 139-bp fragment of the central region of babA2. The babA2 gene was detected in 47.9 % of H. pylori samples. The presence of the babA2 gene was strongly associated with cagA, vacA s1 and vacA m1 genotype. The babA2 status correlated positively with bacterial density score, activity of inflammation and chronic inflammation of gastric mucosa. No significant correlation was found between the babA2 status and the presence of atrophy or intestinal metaplasia. In addition, the activity of gastric inflammation and density score were significantly associated with the coexpression of the cagA, vacA s1, vacA m1 and babA2 genes. The study, which included the largest number of pediatric H. pylori samples to date, confirmed that babA2 gene plays an important role in the pathogenesis of H. pylori gastritis in children. Furthermore, our results suggest that babA2, cagA and vacA s1 and m1 gene products may work synergistically in worsening the inflammation of gastric mucosa.     

Salt-induced changes in the plasma membrane proteome of the halotolerant alga Dunaliella salina as revealed by blue native gel electrophoresis and nano-LC-MS/MS analysis

The halotolerant alga Dunaliella salina is a recognized model photosynthetic organism for studying plant adaptation to high salinity. The adaptation mechanisms involve major changes in the proteome composition associated with energy metabolism and carbon and iron acquisition. To clarify the molecular basis for the remarkable resistance to high salt, we performed a comprehensive proteomics analysis of the plasma membrane. Plasma membrane proteins were recognized by tagging intact cells with a membrane-impermeable biotin derivative. Proteins were resolved by two-dimensional blue native/SDS-PAGE and identified by nano-LC-MS/MS. Of 55 identified proteins, about 60% were integral membrane or membrane-associated proteins. We identified novel surface coat proteins, lipid-metabolizing enzymes, a new family of membrane proteins of unknown function, ion transporters, small GTP-binding proteins, and heat shock proteins. The abundance of 20 protein spots increased and that of two protein spots decreased under high salt. The major salt-regulated proteins were implicated in protein and membrane structure stabilization and within signal transduction pathways. The migration profiles of native protein complexes on blue native gels revealed oligomerization or co-migration of major surface-exposed proteins, which may indicate mechanisms of stabilization at high salinity.     

Spreading and mutability ofSelenomonas ruminantium plasmids

Two small plasmids from Selenomonas ruminantium strain 19D were cloned in Escherichia coli and completely characterized. Sequence comparison indicated that the plasmids are similar to those reported in genetically vaguely related S. ruminantium strain S20. Small 1.4-kb plasmids pSRD191 and pONE430 are only distantly related (approximately 30 % for deduced Rep protein amino acid sequence) but possess a short highly conserved region outside rep gene. Larger plasmids pSRD192 and pONE429 possess large identical DNA regions in an otherwise dissimilar background. Recombination is proposed as an important mechanism of evolution and spreading of S. ruminantium plasmids.     

Structural studies of the O-antigenic polysaccharides from the enteroaggregative Escherichia coli strain 522/C1 and the international type strain from Escherichia coli O 178

The structure of the O-antigenic polysaccharide (PS) from the enteroaggregative Escherichia coli strain 522/C1 has been determined. Component analysis and (1)H and (13)C NMR spectroscopy techniques were used to elucidate the structure. Inter-residue correlations were determined by (1)H,(1)H-NOESY and (1)H,(13)C-heteronuclear multiple-bond correlation experiments. The PS is composed of pentasaccharide repeating units with the following structure: [ structure: see text]. Analysis of NMR data reveals that on average the PS consists of four repeating units and indicates that the biological repeating unit contains an N-acetylgalactosamine residue at its reducing end. Serotyping of the E. coli strain 522/C1 showed it to be E. coli O 178:H7. Determination of the structure of the O-antigen PS of the international type strain from E. coli O 178:H7 showed that the two polysaccharides have identical repeating units. In addition, this pentasaccharide repeating unit is identical to that of the capsular polysaccharide from E. coli O9:K 38, which also contains O-acetyl groups.     

Isolation and sequence analysis of the genomic DNA fragment encoding an aspartic proteinase inhibitor homologue from potato (Solanum tuberosum L.)

A genomic DNA clone encoding an aspartic proteinase inhibitor of potato was isolated from a lambda EMBL3 phage library using the aspartic proteinase inhibitor cDNA as a hybridization probe. The gene has all characteristic sequences normally found in eucaryotic genes. Typical CAAT and TATA box sequences were found in the 5-upstream region. In this part are also two putative regulatory AGGA box sequences located. In the genomic sequence there are no intron sequences interrupting the coding region. An open reading frame of the gene encodes a precursor protein of 217 amino acids which shows high percent identity with the aspartic proteinase inhibitor cDNA.     

Correlation between physico-chemical properties of quaternary ammonium salts of heptacaine and their inhibitory activity against photosynthesizing organisms

Photosynthesis inhibition in algae (Chlorella) and plant (spinach) chloroplasts by quaternary ammonium salts of heptacaine {N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl]-N-alkylpiperidinium bromides} depended on the alkyl chain length of the alkyl substituent and showed good correlations with theoretical hydrophobic fragment constants as well as with experimentally determined physico-chemical parameters, namely extraction constants and surface activities. Communicated by. Z. ŠESTáK     

Two msbB genes encoding maximal acylation of lipid A are required for invasive Shigella flexneri to mediate inflammatory rupture and destruction of the intestinal epithelium

Shigella flexneri is a Gram-negative pathogen that invades and causes inflammatory destruction of the human colonic epithelium, thus leading to bloody diarrhea and dysentery. A type III secretion system that delivers effector proteins into target eukaryotic cells is largely responsible for cell and tissue invasion. However, the respective role of this invasive phenotype and of lipid A, the endotoxin of the Shigella LPS, in eliciting the inflammatory cascade that leads to rupture and destruction of the epithelial barrier, was unknown. We investigated whether genetic detoxification of lipid A would cause significant alteration in pathogenicity. We showed that S. flexneri has two functional msbB genes, one carried by the chromosome (msbB1) and the other by the virulence plasmid (msbB2), the products of which act in complement to produce full acyl-oxy-acylation of the myristate at the 3' position of the lipid A glucosamine disaccharide. A mutant in which both the msbB1 and msbB2 genes have been inactivated was impaired in its capacity to cause TNF-alpha production by human monocytes and to cause rupture and inflammatory destruction of the epithelial barrier in the rabbit ligated intestinal loop model of shigellosis, indicating that lipid A plays a significant role in aggravating inflammation that eventually destroys the intestinal barrier. In addition, neutralization of TNF-alpha during invasion by the wild-type strain strongly impaired its ability to cause rupture and inflammatory destruction of the epithelial lining, thus indicating that TNF-alpha is a major effector of epithelial destruction by Shigella.