Characterization of the desulfurization genes from Rhodococcus sp. strain IGTS8.

Rhodococcus sp. strain IGTS8 possesses an enzymatic pathway that can remove covalently bound sulfur from dibenzothiophene (DBT) without breaking carbon-carbon bonds. The DNA sequence of a 4.0-kb BstBI-BsiWI fragment that carries the genes for this pathway was determined. Frameshift and deletion mutations established that three open reading frames were required for DBT desulfurization, and the genes were designated soxABC (for sulfur oxidation). Each sox gene was subcloned independently and expressed in Escherichia coli MZ1 under control of the inducible lambda pL promoter with a lambda cII ribosomal binding site. SoxC is an approximately 45-kDa protein that oxidizes DBT to DBT-5,5'-dioxide. SoxA is an approximately 50-kDa protein responsible for metabolizing DBT-5,5'-dioxide to an unidentified intermediate. SoxB is an approximately 40-kDa protein that, together with the SoxA protein, completes the desulfurization of DBT-5,5'-dioxide to 2-hydroxybiphenyl. Protein sequence comparisons revealed that the predicted SoxC protein is similar to members of the acyl coenzyme A dehydrogenase family but that the SoxA and SoxB proteins have no significant identities to other known proteins. The sox genes are plasmidborne and appear to be expressed as an operon in Rhodococcus sp. strain IGTS8 and in E. coli.     

Diel variability in catch rate of juvenile flatfish on two small nursery grounds (Port Erin Bay, Isle of Man and Porto Pirn Bay, Faial, Azores)

Variation in beach seine catches was examined in two juvenile flatfish populations (Port Erin, Isle of Man and Porto Pirn, Azores) to determine the importance of diel cycles while controlling for tidal rhythmicity. At Port Erin sampling was undertaken at each low water on consecutive days over a 2-week period in May/June and September 1991. There was no periodicity in the catches of plaice ( Pleuronectes platessa ) in May/June, but in September catches were higher at night. Other flatfish species ( Limanda limanda, Pleuronectes flesus, Scophthalmus maximus and S. rhombus ) sampled at Port Erin were nocturnal. At Porto Pirn, Azores, fish were sampled over 24 h each month from July 1989 to June 1990 and at each low water over a 2-week period in July 1991. The only flatfish species present was Bothuspodas , which had a diurnal pattern in catches over a 1-year period. Sampling at low water in July gave high catches at both midnight and midday.     

Exchange of reduced sulfur gases between lichens and the atmosphere

Fourteen lichens, 10 green algal lichens and four cyanolichens, as well as a cyanobacterium emitted significant quantities of H₂S (0.01–0.04 pmol g dw^–1 s^–1) and DMS (0.005–0.025 pmol g dw^–1 s^–1) but were sinks for COS (0.015–0.14 pmol g dw^–1 s^–1). In contrast, exchange of CH₃SH and CS₂ were sporatic and inconsistent. Although some interspecific variation occurred for the first three gases, exchange rates were relatively uniform and were not influenced by irradiance conditions. In contrast to DMS and H₂S emission, COS uptake was strongly influenced by degree of thallus hydration. Because lichen dominated systems cover extensive terrestrial habitats, COS uptake is potentially important in the world's sulfur budget.     

Involvement of putrescine in the inductive rooting phase of poplar shoots raised in vitro

Micropropagated poplar shoots rooted 100% on a rooting medium (A) containing NAA, but they did not root in the absence of auxin (NA). Putrescine, but not spermidine and spermine, promoted rooting up to 42% when added to the NA medium. Cyclohexylamine (CHA), an inhibitor of spermine synthase, also promoted (up to 36%) rooting in the absence of auxin. The inhibitors of polyamine biosynthesis DFMA (α-difluoromethylarginine) and DFMO (α-difluoromethylomithine), aminoguanidine (AG) and methylglyoxal-bis-guanylhydrazone (MGBG), inhibited rooting when applied in the presence of auxin and had no effect in its absence.
The rooting inductive phase (in the presence of auxin) was determined by periodical transfer of shoots from A to NA medium, and by changes in peroxidase activity, to be 7 h. Putrescine (not spermidine and spermine) accumulated to a maximum during the inductive phase. Both putrescine and CHA promoted rooting on NA medium when applied during the first 7 h. In contrast DFMA and AG inhibited rooting during this period. The results point to the involvement of putrescine and its Δ¹-pyrroline pathway, in the inductive phase of rooting in poplar shoots.     

The Lactococcus lactis sex-factor aggregation gene cluA

A gene, cluA, was cloned from the chromosomally located sex factor of Lactococcus lactis MG1363. Sequence analysis revealed significant homology with previously described aggregation proteins in Enterococcus and Streptococcus species. The possibility that cluA was an equivalent protein involved in cell aggregation between donor and recipient bacteria during lactococcal conjugation was confirmed by its expression under the control of a heterologous promoter in L. lactis. Analysis of the homology between the CluA protein and the related proteins of Enterococcus and Streptococcus allowed a common structure for these proteins to be postulated. This consisted of five domains. Functionally conserved domains I and V act respectively as a secretary leader and C-terminal membrane anchor. Domains II and IV are conserved at the amino acid level and probably have common structural roles whereas domain III is variable and may control binding specificity.     

Polymorphism of the gene encoding the alpha subunit of the stimulatory G-protein of adenylyl cyclase (GNAS1)

A two-allele polymorphism of the human gene encoding for the alpha subunit of the guanine nucleotide-binding protein is described.     

Novel changes in the plasma membrane and cortical cytoplasm during wound-induced contraction in a giant-celled green alga

Summary Changes in the plasma membrane surface and in the cortical cytoplasm during wound healing in giant green algal cells ofErnodesmis verticillata (Kützing) Brgesen were followed using scanning and transmission electron microscopy. Microvillus-like structures that contain cytoplasmic and cytoskeletal constituents were observed emanating from the surface of the plasma membrane at the retracting/cut end of wounded cells. These delicate structures seem to be remnants of cell wall-plasmalemma connections that draw out the plasma membrane and cortical components from the contracting cytoplasm as it pulls away from the cell wall. Most of these connections break during wound healing and, when contraction stops, the microvillus-like protrusions become progressively shorter. In cells treated with a calmodulin antagonist (W-7), a number of distinctive bodies accumulate that are of unknown composition, are oblong in shape, and have a diameter slightly smaller than the protoplasmic protrusions. Ultrastructural and other data indicate that these bodies result from retrieved constituents of the plasma-membrane protrusions, as they do not accumulate in unwounded drugtreated cells or in cells treated in W-5. These findings suggest that the protoplasmic protrusions accumulate membrane and cytoplasmic components that are retrieved and recycled during wound healing inErnodesmis by a novel mechanism. The combined plasma membrane surfaces of the microvillus-like protrusions may help to account for the drastic decrease in surface area that occurs during wound healing.Abbreviations SEM scanning electron microscopy - TEM transmission electron microscopy - W-7 N-[6-aminohexyl]-5-chloro-1-naph-thalenesulfonamide - W-5 N-[6-aminohexyl]-1-naphthalenesulfonamide     

Nucleotide substitutions at the -6 position in the promoter region of the factor IX gene result in different severity of hemophilia B Leyden: consequences for genetic counseling

Mutations in the promoter region of the factor IX gene result in hemophilia B Leyden, which is characterized by considerable improvement in the disease after puberty. We have found that distinct nucleotide substitutions at the -6 position in the Leyden-specific (LS) region are associated with a different severity of hemophilia B. The proband (aged 2) from one family is a severe hemophiliac with factor IX activity (F.IXC) and antigen (F.IXAg) levels less than 1.0U/dl. F.IXC and F.IXAg levels in two affected uncles are approximately 30% of normal levels. The LS region was targeted for analysis because the phenotypes suggested the inheritance of a factor IX Leyden gene. An abnormal TaqI digestion pattern was found in amplified DNA from the proband, and sequencing showed a G (-6) to C transversion that was linked to the disease in the family. In another family, two brothers (aged 8 and 9) suffer from mild hemophilia with F.IXC ranging from 7 to 10 U/dl and F.IXAg from 3 to 4 U/dl. They are the only documented members of the family with a bleeding tendency. Denaturing gradient gel electrophoresis on amplified fragments from one of the patient's genomic DNA corresponding to the 8 exons and flanking sequences of the factor IX gene suggested a defect only in a segment from the 5 region. This segment showed an altered TaqI digestion pattern, and sequencing demonstrated a G(-6) to A transition that was traced to the patients's mother and a grandmother. The different phenotypes associated with the G (-6) to A purine nucleotide transition compared with a G(-6) to C transversion provide evidence that this area is directly involved in the regulation of the human factor IX gene expression in vivo by binding of regulatory factors. The ability to predict that the conditions of a hemophilia B patient will improve with age has important implications for genetic counseling of the family. Therefore, the LS region should always be included when scanning the factor IX gene for mutations.     

Environmental conditions during glycerol bioconversion affect 3-hydroxypropionic acid bioproduction by Limosilactobacillus reuteri DSM 17938

3-Hydroxypropionic acid (3-HP) is a platform molecule whose biological production was carried out by the bacterium Limosilactobacillus reuteri according to a two-step process: first, a growth phase in batch mode on glucose, then a glycerol bioconversion into 3-HP in fed-batch mode. With the objective of improving 3-HP bioproduction, this study aimed at defining the operating conditions during the bioconversion phase that increases the bioproduction performance. A central composite rotatable design allowed testing various pH levels and specific glycerol feeding rates. By establishing response surfaces, optimal conditions have been identified that were different depending on the considered output variable (final 3-HP quantity, 3-HP production yield and production rate). Of them, 3-HP final quantity and 3-HP production yield were maximized at pH 6.0 and at specific glycerol feeding rates of 60 and 55 mg_gly g_CDW⁻¹ h⁻¹, respectively. The specific 3-HP production rate was the highest at the upper limit of the specific substrate feeding rate (80 mg_gly g_CDW⁻¹ h⁻¹) but was not affected by the pH. An additional experiment was carried out at pH 6.0 and a specific glycerol feeding rate of 80 mg_gly g_CDW⁻¹ h⁻¹ to validate the previous observations. In conclusion, the results showed a significant improvement of 3-HP concentration by 13%, of specific production rate by 34% and of 3-HP volumetric productivity by 39%, as compared to the initial values.     

First chromosome scale genomes of ithomiine butterflies (Nymphalidae: Ithomiini): Comparative models for mimicry genetic studies

The ithomiine butterflies (Nymphalidae: Danainae) represent the largest known radiation of Müllerian mimetic butterflies. They dominate by number the mimetic butterfly communities, which include species such as the iconic neotropical Heliconius genus. Recent studies on the ecology and genetics of speciation in Ithomiini have suggested that sexual pheromones, colour pattern and perhaps hostplant could drive reproductive isolation. However, no reference genome was available for Ithomiini, which has hindered further exploration on the genetic architecture of these candidate traits, and more generally on the genomic patterns of divergence. Here, we generated high-quality, chromosome-scale genome assemblies for two Melinaea species, M. marsaeus and M. menophilus, and a draft genome of the species Ithomia salapia. We obtained genomes with a size ranging from 396 to 503 Mb across the three species and scaffold N50 of 40.5 and 23.2 Mb for the two chromosome-scale assemblies. Using collinearity analyses we identified massive rearrangements between the two closely related Melinaea species. An annotation of transposable elements and gene content was performed, as well as a specialist annotation to target chemosensory genes, which is crucial for host plant detection and mate recognition in mimetic species. A comparative genomic approach revealed independent gene expansions in ithomiines and particularly in gustatory receptor genes. These first three genomes of ithomiine mimetic butterflies constitute a valuable addition and a welcome comparison to existing biological models such as Heliconius, and will enable further understanding of the mechanisms of adaptation in butterflies.