Radioimmunoassay of neuropeptide Y

The development of a radioimmunoassay to the newly isolated peptide, neuropeptide Y is described. Four separate antisera have been developed using different immunisation schedules. Two of these antisera (YNI and YNIO) are directed to the C-terminal region of the peptide and cross-react with the related peptide PYY, whereas YN7 is specific being directed to the N-terminal region of NPY, YN6 is similarly specific for NPY, but is unable to bind the available fragments. These four antisera provide similar results for determination of NPY immunoreactivity within porcine brain extracts, however YN6 consistently undervalues all extracts from the other species examined (human, rat, guinea pig, cat and mouse). Chromatographic analysis by means of reverse phase high pressure liquid chromatography (HPLC) shows that NPY immunoreactivity of human extracts elutes in an earlier position than the porcine standard. It seems likely therefore that human and porcine NPY differ in their amino acid sequences.     

The role of membrane lectins in Dictyostelium discoideum aggregation as ascertained by specific univalent antibodies against discoidin I

Antibodies against pure discoidin I have been used as a tool to ascertain the role of this lectin in aggregation of Dictyostelium discoideum. Discoidin I is widely expressed over the cell surface of aggregation-competent AX-2 cells, as ascertained by indirect immunofluorescence with specific (antidiscoidin I) antibodies. Univalent antidiscoidin I antibodies (Fab fragments) inhibit the aggregation-specific intercellular adhesion of D discoideum AX-2 cells in an in vitro assay. This inhibition depends on antibody concentration and cell density; a 50% inhibition of cell aggregation was obtained at antidiscoidin I Fab concentration of 4.5 mg/ml and 1 X 10(6) cells/ml. Aggregation and morphogenesis on solid support is also effectively inhibited when AX-2 cells are starved in the presence of antidiscoidin I Fab fragments. The inhibition of morphogenesis is also dose dependent and more effective than in the in vitro assay. No inhibition of aggregation either in the in vitro assay or on morphogenesis on solid support was observed with preimmune Fab fragments at any of the concentrations tested (up to 9.6 mg/ml).     

Physical map of DNA from a new cauliflower mosaic virus strain

The restriction enzymes AluI, BamHI, BglII, EcoRI, HindIII, and SalI have been used to characterize and map a new cauliflower mosaic virus strain (Cabb-S). These fragments have been ordered by examining their overlapping regions after double enzymatic digestion. The single SalI cleavage site was chosen as the point of origin. We compare this strain with those already described.     

The amino acid sequences of plastocyanin from Mercurialis perennis and Capsella bursa-pastoris

The amino acid sequences of the plastocyanins from Mercurialis perennis and Capsella bursa-pastoris have been determined. The amides at positions 64 and 68 in the Mercurialis sequence were positioned by ‘homology’ Both proteins are single polypeptide chains of 99 residues and are closely related to other higher plant plastocyanins.     

Genetics of seed-coat colour in Citrullus lanatus (Thunb.) Mansf.

Summary Intervarietal crosses in watermelon, Citrullus lanatus (Thunb.) Mansf., involving six parents with black (J18-1 and J 75), brown (J56-1 and N.H. Midget), red (Bykovski-199) or light cream (Red Nectar) seed-coat colour were made. Parents, F₁, F₂ and backcross populations were evaluated for their phenotypic expressions with regard to the seed-coat colours involved. Black colour was monogenically dominant over brown light cream and red colour of seed-coat separately or independently. Red colour was dominant over light cream colour of seed-coat by a single pair of genes. The light cream colour was recessive to the brown seed-coat colour of watermelon where a single pair of genes was involved.     

Regulation of B lymphocyte activation by the Fc portion of immunoglobulin

Murine splenic B lymphocytes are induced to proliferate and undergo polyclonal activation in the presence of Fc fragments, AHGG, antigen-antibody complexes, and CH₃ fragments derived from plasmin digestion of human Ig. The unifying feature of the polyclonal antibody response induced by these agents is that in all cases a portion of the constant region of the Ig molecule (ie, Fc region) is present. Fragments of Ig lacking the Fc piece, such as Fab and F(ab′)₂ were found not to be stimulatory. In addition, a model is proposed to account for the regulatory effects of antigen-antibody complexes on an ongoing humoral immune response.     

Regulation of excitation energy distribution in Photosystem-II fragments by magnesium ions

Fluorescence characteristics of Photosystem-II subchloroplasts (TSF-II and TSF-IIa) fractionated by Triton X-100 treatment were studied in relation to cation-induced regulation of excitation-energy distribution within subchloroplast fragments. Absorption spectra and fluorescence-emission spectra at 77 K showed that TSF-II contains the light-harvesting chlorophyll-protein complex in addition to the reaction-center complex, which is present alone in TSF-IIa.Mg²⁺ increased the ratio of F_695nm to F_685nm in the fluorescence-emission spectrum of TSF-II particles at 77 K, but had no effect on TSF-IIa particles. Mg²⁺ also induced a quenching of chlorophyll fluorescence at room temperature in TSF-II, an effect that was insensitive to the presence of DCMU. The DCMU-insensitive fluorescence quenching was not observed in the TSF-IIa preparation. These results suggest an existence of cation-induced regulation of excitation-energy transfer in TSF-II preparations. Presence of antenna chlorophyll molecules alone does not seem to be sufficient for observing energytransfer regulation by cations in Photosystem-II preparations.     

Evidence of horizontal gene transfer between land plant plastids has surprising conservation implications

Background and AimsHorizontal gene transfer (HGT) is an important evolutionary mechanism because it transfers genetic material that may code for traits or functions between species or genomes. It is frequent in mitochondrial and nuclear genomes but has not been demonstrated between plastid genomes of different green land plant species.MethodsWe Sanger-sequenced the nuclear internal transcribed spacers (ITS1 and 2) and the plastid rpl16 G2 intron (rpl16). In five individuals with foreign rpl16 we also sequenced atpB-rbcL and trnL_UAA-trnF_GAA.Key ResultsWe discovered 14 individuals of a moss species with typical nuclear ITSs but foreign plastid rpl16 from a species of a distant lineage. None of the individuals with three plastid markers sequenced contained all foreign markers, demonstrating the transfer of plastid fragments rather than the entire plastid genome, i.e. entire plastids were not transferred. The two lineages diverged 165–185 Myr BP. The extended time interval since lineage divergence suggests that the foreign rpl16 is more likely explained by HGT than by hybridization or incomplete lineage sorting.ConclusionsWe provide the first conclusive evidence of interspecific plastid-to-plastid HGT among land plants. Two aspects are critical: it occurred at several localities during the massive colonization of recently disturbed open habitats that were created by large-scale liming as a freshwater biodiversity conservation measure; and it involved mosses whose unique life cycle includes spores that first develop a filamentous protonema phase. We hypothesize that gene transfer is facilitated when protonema filaments of different species intermix intimately when colonizing disturbed early succession habitats.