Local grassland restoration affects insect communities

1. It is hypothesised that ecological restoration in grasslands can induce an alternative stable state shift in vegetation. The change in vegetation influences insect community assemblages and allows for greater functional redundancy in pollination and refuge for native insect species. 2. Insect community assemblages at eight coastal California grassland sites were evaluated. Half of these sites had undergone restoration through active revegetation of native grassland flora and half were non‐restored. Insects were collected from Lupinus bicolor (Fabaceae) within 2 × 2‐m² plots in spring 2017. Lupinus bicolor is a common native species that is used in California restoration projects, and home and state landscaping projects. 3. Ordination demonstrated that insect community assemblages were different between restored and non‐restored sites. These differences were seen in insect functional groups as well as taxa‐specific differences and were found to be driven by environmental characteristics such as non‐native forb cover. 4. Functional redundancy of herbivores decreased at restored sites, while pollinators became more redundant compared with non‐restored sites. The assemblages of the common species found at restoration sites contained more native insects than those found at non‐restored sites, including species such as Bombus vosnesenskii. 5. Local grassland restoration has the potential to induce an alternative stable state change and affect insect community assemblages. Additionally, it was found that grassland restoration can be a potential conservation tool to provide refugia for bumblebees (Bombus), but additional studies are required to fully understand its broader applicability.     

Bacteriophage-resistance mechanisms examined by transfection of Lactococcus lactis subsp. lactis 4513-5 mediated by high voltage electroporation

Summary Phage adsorption tests and transfection by electroporation were carried out to decide whether phage-resistance in Lactococcus lactis subsp. lactis strain 4513-5 is based on intracellular or extracellular mechanisms. Using high voltage (12.5 kV/cm) electroporation, untreated phage DNA was introduced into phage-sensitive and phage-resistant cells. Since phages showed low adsorption frequencies on resistant bacteria, resistance is localized in the cell wall preventing phage DNA from entering the cell. This is the only mechanism responsible for the resistance of L. lactis subsp. lactis 4513-5 against its homologous phage P4513-K12 and non-homologous phages P05M-13 and P05M-47, but not against phage P530-7 and phage P530-12. In the case of the latter two phage strains, intracellular resistance mechanisms are involved and discussed.     

Sieve-element characters of Myristicaceae: Nuclear crystals, S-and P-type plastids, nacreous walls

The phloem of the Myristicaceae is composed of sieve elements, parenchymatous cells, and fibers. Within the metaphloem and secondary phloem parenchymatic layers including prominent secretory elements alternate with tangential bands of fibers and layers composed of sieve elements, companion cells and phloem-parenchyma cells. among the latter the sieve elements are most abundant and easily identified by the presence of thick (nacreous) walls. The most characteristic feature of the sieve elements of Myristicaceae (and found nowhere else among the Magnoliiflorae) are nuclear crystals, which are released into the lumen during nuclear degeneration and persist in the mature cell. P-and S-type sieve-element plastids were recorded for the 18 species investigated. Both types of the plastid are characterized by large diameters and many medium-sized starch grains. The sizes and contents (small protein crystals only) of the P-type plastids of the Myristicaceae do not conform to the tiny P-type plastids (with large protein crystals) of the Annonaceae, a family to which the Myristicaceae is traditionally allied.     

The role of aromatic side chain residues in micelle binding by pancreatic colipase. Fluorescence studies of the porcine and equine proteins.

Fluorescence techniques have been employed to study the interaction of porcine and equine colipase with pure taurodeoxycholate and mixed micelles. Nitrotyrosine-55 of porcine colipase is obtained by modification with tetranitromethane (low excess, in the presence of taurodeoxycholate) of the protein followed by gel filtration and ion-exchange chromatography. Verification of the residue modified was obtained by h.p.l.c. peptide purification and sequence analysis. Reduction and quantitative reaction with dansyl chloride yields a fluorescent derivative that is twice as active in conjunction with lipase as is native colipase and that exhibits a strong emission band at 550 nm. Addition of micellar concentrations of taurodeoxycholate causes a 4.3-fold increase in the emission maximum as well as a 70 nm blue shift to 480 nm. Inclusion of oleic acid to form a mixed micelle reduces these spectral effects. Scatchard analysis of the data yield a Kd of 6.8 X 10(-4) M and a single colipase-binding site for taurodeoxycholate micelles. The data, by analogy to a phospholipase system, are consistent with a direct insertion of dansyl-NH-tyrosine-55 into the micelle. The presence of a single tryptophan residue (Trp-52) in equine colipase provides an intrinsic fluorescent probe for studying protein-micelle interaction. The emission maximum of horse colipase at 345 nm indicates a solvent-accessible tryptophan residue which becomes less so on binding of micelles. A blue shift of 8 nm and a 2-fold increase in amplitude is indicative of a more hydrophobic environment for tryptophan induced by taurodeoxycholate micelles. There is also a decrease in KSV for acrylamide quenching in the presence of micelles, which further supports a loss of solvent accessibility. The most dramatic pH effects are observed with KI quenching, and may indicate the presence of negative charges near Trp-52.     

Cultivar-related differences in the distribution of cell-wall-bound thionins in compatible and incompatible interactions between barley and powdery mildew

Leaf-specific thionins of barley (Hordeum vulgare L.) have been identified as a novel class of cell-wall proteins toxic to plant-pathogenic fungi and possibly involved in the defence mechanism of plants. The distribution of these polypeptides has been studied in the host-pathogen system of barley and Erisyphe graminis DC.f.sp. hordei Marchal (powdery mildew). Immunogold-labelling of thionins in several barley cultivars indicates that resistance or susceptibility may be attributed to the presence or absence of thionins at the penetration site in walls and papillae of epidermal leaf cells.All of the leaf-specific thionin genes are confined to the distal end of the short arm of chromosome 6 of barley. None of the genes for cultivarspecific resistance to powdery mildew which have previously been mapped on barley chromosomes are found close to this locus.     

Heligmosomoides polygyrus or Nematospiroides dubius?

The intestinal trichostrongylid nematode of mice, Heligmosomoides polygyrus bakeri, is often referred to as Nematospiroides dubius. Here, Jerzy Behnke, Anne Keymer and John Lewis ask the question: which is correct?     

Characterization of the minimal origin required for replication of the streptococcal plasmid plP501 in Bacillus subtilis

By using deletional analysis the origin of replication, oriR, of the streptococcal plasmid pIP501 in Bacillus subtilis has been mapped at a position immediately downstream of the repR gene. Determination of both the right and left border of oriR allowed the definition of a sequence of a maximum of 52 nucleotides which theoretically constitutes the minimal origin of replication. Recently, the start point of leading-strand synthesis of the closely related plasmid pAM beta 1 has been mapped at a position which is located exactly in the middle of this sequence (Bruand et al., 1991). The function of oriR did not depend on its location downstream of the repR gene. Translocation of oriR-containing fragments to other regions of the plasmid proved to be possible. The smallest translocated fragment that still reconstituted autonomous replication was 72bp in size. This fragment was also active in directing the replication of an Escherichia coli plasmid in B. subtilis when the RepR protein was supplied in trans from a repR gene integrated into the host chromosome. The transformation efficiency of plasmids carrying translocated oriR fragments showed a certain dependence on the fragment length and orientation. The DNA sequence of oriR included an inverted repeat, both branches of which appeared to be essential for oriR function. The repeats of oriR shared sequence similarity with a repeat located upstream of promoter pII, which has been suggested to be involved in autoregulation of repR expression.     

DNA polymerase alpha-DNA primase from human lymphoblasts

The DNA polymerase alpha-DNA primase complex from the human lymphoblast line HSC93 has been enriched to near homogeneity by using an immunoaffinity purification protocol which was developed earlier for the purification of the calf thymus enzyme (Nasheuer, H.-P. and Grosse, F. (1987) Biochemistry 26, 8458-8466). Immunoaffinity purified polymerase-primase from human cells consisted of four subunits displaying molecular weights of 195,000 and 180,000 for the DNA synthesizing alpha-subunit, of 68,000 for the beta-subunit, and of 55,000 and 48,000 for the primase-carrying gamma- and delta-subunit, respectively. The isoelectric pH values for the individual subunits were estimated from non-equilibrium pH gradients to be between 5.9 and 5.7 for the alpha-subunit, at 5.5 for the beta-subunit, and at 7.5 and 8.0 for the gamma- and delta-subunit, respectively. The purified polymerase-primase converted single-stranded phi X174 DNA into the double-stranded form in a primase-initiated reaction. During this process, 3-10 RNA primers were formed. RNA primers were about 11 nucleotides long. Elongation of existing RNA primers by the human polymerase-primase was semi-processive; following primer binding the DNA polymerase continuously incorporated 20 to 50 nucleotides, then it dissociated from the template DNA.