Immobilization of the Glycosylphosphatidylinositol-anchored Gas1 Protein into the Chitin Ring and Septum Is Required for Proper Morphogenesis in Yeast

Gas1p is a glucan-elongase that plays a crucial role in yeast morphogenesis. It is predominantly anchored to the plasma membrane through a glycosylphosphatidylinositol, but a fraction was also found covalently bound to the cell wall. We have used fusions with the green fluorescent protein or red fluorescent protein (RFP) to determine its localization. Gas1p was present in microdomains of the plasma membrane, at the mother-bud neck and in the bud scars. By exploiting the instability of RFP-Gas1p, we identified mobile and immobile pools of Gas1p. Moreover, in chs3Δ cells the chitin ring and the cross-linked Gas1p were missing, but this unveiled an additional unexpected localization of Gas1p along the septum line in cells at cytokinesis. Localization of Gas1p was also perturbed in a chs2Δ mutant where a remedial septum is produced. Phenotypic analysis of cells expressing a fusion of Gas1p to a transmembrane domain unmasked new roles of the cell wall-bound Gas1p in the maintenance of the bud neck size and in cell separation. We present evidence that Crh1p and Crh2p are required for tethering Gas1p to the chitin ring and bud scar. These results reveal a new mechanism of protein immobilization at specific sites of the cell envelope.     

Identification and distribution of heparan sulfate proteoglycans in the white muscle of Atlantic cod (Gadus morhua) and spotted wolffish (Anarhichas minor)

Heparan sulfate proteoglycans (HSPGs) were identified in pre-rigor muscle of two species of cold water fish, Atlantic cod (Gadus morhua) and spotted wolffish (Anarhichas minor) by biochemical and immunological methods. The distribution was described by immunohistology. Special emphasis was directed to the extracellular matrix (ECM) HSPGs perlecan and agrin. In vivo ³⁵S-sulfate labeling combined with ultracentrifugation in CsCl₂, DEAE chromatography and scintillation counting of the eluates, revealed that the content of ³⁵S-labeled PGs was much higher in wolffish than in cod. A considerable proportion of the ³⁵S-sulfated PGs in both species was HSPG, as judged by nitrous acid degradation. HSPG represented, however, a higher proportion of the ³⁵S-sulfated PGs in cod compared to wolffish. Dot blot and electrophoresis/western blot using two different HS-mAbs, 10E4 and HepSS-1 indicated structural differences in the HS-chains of the PGs present. This observation was strengthened by immunohistochemistry, showing that both mAbs detected epitopes in the pericellular area, but the staining patterns were not superimposable. Two different agrin isoforms were identified in both species. Furthermore, in the white muscle of both cod and wolffish, perlecan mAb (A7L6) showed positive staining restricted to the transition between myocommata and myofibers.     

Interaction of KNAT6 and KNAT2 with BREVIPEDICELLUS and PENNYWISE in Arabidopsis inflorescences

The three amino acid loop extension (TALE) homeodomain superfamily, which comprises the KNOTTED-like and BEL1-like families, plays a critical role in regulating meristem activity. We previously demonstrated a function for KNAT6 (for KNOTTED-like from Arabidopsis thaliana 6) in shoot apical meristem and boundary maintenance during embryogenesis. KNAT2, the gene most closely related to KNAT6, does not play such a role. To investigate the contribution of KNAT6 and KNAT2 to inflorescence development, we examined their interactions with two TALE genes that regulate internode patterning, BREVIPEDICELLUS (BP) and PENNYWISE (PNY). Our data revealed distinct and overlapping interactions of KNAT6 and KNAT2 during inflorescence development. Removal of KNAT6 activity suppressed the pny phenotype and partially rescued the bp phenotype. Removal of KNAT2 activity had an effect only in the absence of both BP and KNAT6 or in the absence of both BP and PNY. Consistent with this, KNAT6 and KNAT2 expression patterns were enlarged in both bp and pny mutants. Thus, the defects seen in pny and bp are attributable mainly to the misexpression of KNAT6 and to a lesser extent of KNAT2. Hence, our data showed that BP and PNY restrict KNAT6 and KNAT2 expression to promote correct inflorescence development. This interaction was also revealed in the carpel.     

Effects of ionizing radiation and modified atmosphere packaging on the shelf life of aqua-cultured sea bass (Dicentrarchus labrax)

The major problems concerning marketing and distribution of seafoods are their high perishability due mainly to contamination by spoilage and pathogenic microorganisms. The reduction, destruction or inhibition of microbial contaminants using single or combined treatments might lead to efficient preservation methods. In this research we examined the feasibility of modified atmosphere packaging and irradiation treatments on the extension of the shelf-life of fresh aqua-cultured sea bass Dicentrarchus labrax species. The quality and the freshness of sea bass packaged in modified atmosphere or γ-irradiated were evaluated by assessing their microbiological, sensory and chemical properties. The gas mixture composed by 60:35:5 CO₂/N₂/O₂ resulted as the best inhibitory treatment to extend the shelf life of sea bass. A major MDA containment and microbial decontamination in irradiated samples at 3 kGy were also found in respect to the control samples.     

PHOTOINHIBITION OF PSII IN EMILIANIA HUXLEYI (HAPTOPHYTA) UNDER HIGH LIGHT STRESS: THE ROLES OF PHOTOACCLIMATION,PHOTOPROTECTION, AND PHOTOREPAIR1

The response of the coccolithophorid Emiliania huxleyi (Lohmann) W. H. Hay et H. Mohler to acute exposure to high photon flux densities (PFD) was examined in terms of PSII photoinhibition, photoprotection, and photorepair. The time and light dependencies of these processes were characterized as a function of the photoacclimation state of the alga. Low‐light (LL) acclimated cells displayed a higher degree of photoinhibition, measured as decline in F_v/F_m, than high‐light (HL) acclimated cells. However, HL cultures were more susceptible to photodamage but also more capable of compensating for it by performing a faster repair cycle. The relation between gross photoinhibition (observed in the presence of an inhibitor of repair) and PFD to which the algae were exposed deviated from linearity at high PFD, which calls into question the universality of current concepts of photoinhibition in mechanistic models. The light dependence of the de‐epoxidation state (DPS) of the xanthophyll cycle (XC) pigments on the timescale of hours was the same in cells acclimated to LL and HL. However, HL cells were more efficient in realizing nonphotochemical quenching (NPQ) on short timescales, most likely due to a larger XC pool. LL cells displayed an increase in the PSII effective cross‐section (σ_PSII) as a result of photoinhibition, which was observed also in HL cells when net photoinhibition was induced by blocking the D1 repair cycle. The link between σ_PSII and photoinhibition suggests that the population of PSII reaction centers (RCIIs) of E. huxleyi shares a common antenna, according to a “lake” organization of the light‐harvesting complex.     

Couplings and recouplings of four angular momenta: Alternative 9<Emphasis Type="Italic">j</Emphasis> symbols and spin addition diagrams

The Wigner 9j symbols of the first kind—also known as Fano X-coefficients—serve to connect different addition schemes of four angular momenta, widely known examples being the LS and the jj couplings in atomic, molecular, and nuclear spectroscopies. Here, we also consider alternative sequences of binary couplings of four angular momenta, which are dealt through the 9j symbols of the second kind, and are explicitly given by the pentagonal (or Biedenharn–Elliott) identity. These coefficients are essential ingredients in the quantum-mechanical treatments of rotational and polarization phenomena in reaction dynamics and photoinduced processes. We also emphasize the combinatorial structure underlying the extended construction of a previously introduced truncated icosahedral “abacus”, and provide extensions useful for algebraical manipulations, semiclassical interpretations, and computational applications, including all the 120 addition schemes.     

Genetic identification of wild and domestic cats (Felis silvestris) and their hybrids using Bayesian clustering methods

Crossbreeding with free-ranging domestic cats is supposed to threaten the genetic integrity of wildcat populations in Europe, although the diagnostic markers to identify "pure" or "admixed" wildcats have never been clearly defined. Here we use mitochondrial (mt) DNA sequences and allelic variation at 12 microsatellite loci to genotype 128 wild and domestic cats sampled in Italy which were preclassified into three separate groups: European wildcats (Felis silvestris silvestris), Sardinian wildcats (Felis silvestris libyca), and domestic cats (Felis silvestris catus), according to their coat color patterns, collection localities, and other phenotypical traits, independently of any genetic information. For comparison, we included some captive-reared hybrids of European wild and domestic cats. Genetic variability was significantly partitioned among the three groups (mtDNA estimate of F(ST) = 0.36; microsatellite estimate of R(ST) = 0.30; P < 0.001), suggesting that morphological diversity reflects the existence of distinct gene pools. Multivariate ordination of individual genotypes and clustering of interindividual genetic distances also showed evidence of distinct cat groups, partially congruent with the morphological classification. Cluster analysis, however, did not enable hybrid cats to be identified from genetic information alone, nor were all individuals assigned to their populations. In contrast, a Bayesian admixture analysis simultaneously assigned the European wildcats, the Sardinian wildcats, and the domestic cats to different clusters, independent of any prior information, and pointed out the admixed gene composition of the hybrids, which were assigned to more than one cluster. Only one putative Sardinian wildcat was assigned to the domestic cat cluster, and one presumed European wildcat showed mixed (hybrid) ancestry in the domestic cat gene pool. Mitochondrial DNA sequences indicated that three additional presumed European wildcats might have hybrid ancestry. These four cats were sampled from the same area in the northernmost edge of the European wildcat distribution in the Italian Apennines. Admixture analyses suggest that wild and domestic cats in Italy are distinct, reproductively isolated gene pools and that introgression of domestic alleles into the wild-living population is very limited and geographically localized.     

Detection of same sized 4.3 Kb extrachromosomal DNA elements in weakly beta-haemolytic human intestinal spirochaetes and Serpulina pilosicoli of swine origin

Agarose gel electrophoresis of total DNA from Italian strains of weakly beta-haemolytic human intestinal spirochaetes (w beta HIS) and porcine Serpulina pilosicoli reference strain P43/6/78 showed an extrachromosomal band having the same size and migrating at 4.3 Kb. The same results were observed after agarose gel electrophoresis of DNA obtained from the supernatant fluids of the spirochaetal cultures analysed. Swine Serpulina hyodysenteriae reference strain P18A was comparatively analysed and a 6.5 Kb extrachromosomal DNA element was found, as expected. Furthermore, S. hyodysenteriae reference strain P18A differed from all the other spirochaetes tested and had a higher number of flagella (8-12) at each cell end and was strongly beta-haemolytic. To the best of our knowledge, this is the first report on the detection of a band of extrachromosomal DNA having the same size in w beta HIS and S. pilosicoli from swine origin.     

Resistance and Raman spectroscopy analysis of Parageobacillus thermantarcticus spores after γ-ray exposure

Spores of the genus Bacillus are able to resist ionizing radiations and therefore they are a suitable biological model for studies in Astrobiology, i.e. the multidisciplinary approach to the study of the origin and evolution of life on Earth and in the universe. The resistance to γ-radiation is an important issue in Astrobiology in relation to the search for bacterial species that could adapt to life in space. This study investigates the resistance of spores of the thermophilic bacteria Parageobacillus thermantarcticus to γ-rays. The analysis of spores’ response to irradiation at a molecular level is performed by means of Raman spectroscopy that allows to get insights in the sequence of events taking place during inactivation. The role of the γ-rays’ dose in the inactivation of spores is also investigated, allowing to highlight the mechanism(s) of inactivation including DNA damage, protein denaturation and calcium dipicolinate levels.