Relationship between a host plant compound,myrcene and pheromone production in the bark beetle, IPS paraconfusus

The pheromonal components, ipsenol and ipsdienol were found in increasing quantities in hindguts of only the male sex of Ips paraconfusus following exposure of both sexes to a series of increasing concentrations of myrcene vapour. Hindguts of female and male beetles contained similar quantities of myrcene and other volatile compounds associated with myrcene exposure. Unexposed beetles of both sexes did not contain detectable amounts of any volatile compound. This indicates that myrcene induces or is a precursor for sex-specific pheromone biosynthesis.     

Maxicircle DNA and edited mRNA sequences of closely related trypanosome species: implications of kRNA editing for evolution of maxicircle genomes.

kRNA editing produces functional mRNAs by uridine insertion and deletion. We analyzed portions of the apocytochrome b and NADH dehydrogenase subunits 7 and 8 (ND7 and 8) genes and their edited mRNAs in Trypanosoma congolense and compared these to the corresponding sequences in T.brucei. We find that these genes are highly diverged between the two species, especially in the positions of thymidines and in nucleotide transitions. Editing eliminates differences in encoded uridines producing edited mRNAs that are identical except for the nucleotide substitutions. The resulting predicted proteins are identical since all nucleotide substitutions are silent. A T.congolense minicircle-encoded gRNA which can specify editing of ND8 mRNA was identified. This gRNA can basepair with both T.congolense and T.brucei ND8 mRNA despite nucleotide transitions due to the flexibility of G:U base-pairing. These results illustrate how editing affects the characteristics of maxicircle sequence divergence and allows protein sequence conservation despite a level of DNA sequence divergence which would be predicted to be intolerable in the absence of editing.     

Light-induced increase in the number and activity of ribosomes bound to pea chloroplast thylakoids in vivo

Within 8 to 10 minutes of illumination, chloroplast thylakoids of pea (Pisum sativum) became enriched 30 to 100% in ribosomes bound by nascent chains. Following (or, in some experiments, coincident with) this apprarent redistribution was a 25 to 65% increase in the total bound ribosome population, which was then maintained at this higher level during the normal light period. On transfer of plants to darkness, the bound ribosome population decreased to the lower dark level. White, blue (400 to 520 nanometers), and orange (545 to 690 nanometers) light were all effective in producing an increase in the bound ribosome population. The level of bound ribosomes in the oldest leaves of 16-day-old plants was 15-fold less than in the still-maturing leaf but was still increased by illumination.     

Frizzled and Dfrizzled-2 function as redundant receptors for Wingless during Drosophila embryonic development.

In cell culture assays, Frizzled and Dfrizzled2, two members of the Frizzled family of integral membrane proteins, are able to bind Wingless and transduce the Wingless signal. To address the role of these proteins in the intact organism and to explore the question of specificity of ligand-receptor interactions in vivo, we have conducted a genetic analysis of frizzled and Dfrizzled2 in the embryo. These experiments utilize a small gamma-ray-induced deficiency that uncovers Dfrizzled2. Mutants lacking maternal frizzled and zygotic frizzled and Dfrizzled2 exhibit defects in the embryonic epidermis, CNS, heart and midgut that are indistinguishable from those observed in wingless mutants. Epidermal patterning defects in the frizzled, Dfrizzled2 double-mutant embryos can be rescued by ectopic expression of either gene. In frizzled, Dfrizzled2 mutant embryos, ectopic production of Wingless does not detectably alter the epidermal patterning defect, but ectopic production of an activated form of Armadillo produces a naked cuticle phenotype indistinguishable from that produced by ectopic production of activated Armadillo in wild-type embryos. These experiments indicate that frizzled and Dfrizzled2 function downstream of wingless and upstream of armadillo, consistent with their proposed roles as Wingless receptors. The lack of an effect on epidermal patterning of ectopic Wingless in a frizzled, Dfrizzled2 double mutant argues against the existence of additional Wingless receptors in the embryo or a model in which Frizzled and Dfrizzled2 act simply to present the ligand to its bona fide receptor. These data lead to the conclusion that Frizzled and Dfrizzled2 function as redundant Wingless receptors in multiple embryonic tissues and that this role is accurately reflected in tissue culture experiments. The redundancy of Frizzled and Dfrizzled2 explains why Wingless receptors were not identified in earlier genetic screens for mutants defective in embryonic patterning.     

Galactosyl-binding lectins from the tunicate Didemnum candidum. Purification and physicochemical characterization

The plasma of the ascidian Didemnum candidum possesses lectin activity directed toward galactosyl moieties. We report the purification by affinity chromatography, the physicochemical properties, amino acid composition, and partial N-terminal amino acid sequence of two galactosyl-binding lectins D. candidum lectins I and II (DCL-I and DCL-II) from the plasma of this protochordate species. Both lectins were purified by affinity chromatography (on acid-treated Sepharose 4B and asialofetuin conjugated to Sepharose 4B) to homogeneity as judged by immunoelectrophoresis, size exclusion chromatography on high performance liquid chromatography, and polyacrylamide gel electrophoresis. Isoelectric focusing in polyacrylamide gels revealed that DCL-I focuses as a family of bands at pH 3.8-5.2, while DCL-II focuses at pH 9.2-10.2. Gas chromatography analyses of alditol acetate derivatives indicated that no carbohydrate components are associated with the lectins. Approximate subunit molecular weights estimated by polyacrylamide gel electrophoresis and size exclusion chromatography on high performance liquid chromatography in 6 M guanidine HCl under reducing conditions were 13,400-14,500 for DCL-I and 14,500-15,500 for DCL-II. Native molecular weights estimated by sedimentation equilibrium were 56,600 (DCL-I) and 57,500 (DCL-II), indicating that both species are constituted by four equal-sized subunits. Frictional ratios suggested that both lectins are globular proteins. Using rabbit antisera, the two molecules appeared serologically distinct. The extinction coefficient for DCL-I was E280 mg/ml = 2.52 ml mg-1 cm-1. Circular dichroism analyses of DCL-I suggested 29% alpha-helix and 37% beta-structure in the protein. Excitation/emission fluorescence spectra for DCL-I yielded maximum excitation and emission wavelengths at 288 and 330 nm, respectively. Amino acid compositions of DCL-I and DCL-II differed mainly in the proportions of aspartic and glutamic acids, serine, alanine, cysteine, valine, phenylalanine, and histidine. Amino acid compositions of DCL-I and DCL-II were compared to each other and to immunoglobulins and putative recognition molecules by the parameter S delta Q. DCL-I exhibited similarities in amino acid composition to lectins from the tunicate Halocynthia pyriformis, the lamprey Petromyzon marinus, and the horseshoe crab Carcinoscorpius rotundicauda, rabbit C-reactive protein, and lamprey and carp immunoglobulin mu chains. DCL-II showed amino acid composition and similarities with several fish immunoglobulin light chains, immunoglobulin-related molecules isolated from mouse and marmoset T cells, and carp and goldfish immunoglobulin heavy chains.(ABSTRACT TRUNCATED AT 400 WORDS)     

Expression, purification, and kinetic characterization of full-length human fibroblast activation protein

Human fibroblast activation protein (FAP), an integral membrane serine protease, was produced in insect cells as a hexa-His-tagged protein using a recombinant baculovirus expression system. Two isoforms of FAP, glycosylated and nonglycosylated, were identified by Western blotting using an anti-His-tag antibody and separated by lectin chromatography. The glycosylated FAP was purified to near homogeneity using immobilized metal affinity chromatography and was shown to have both postprolyl dipeptidyl peptidase and postgelatinase activities. In contrast, the nonglycosylated isoform demonstrated no detectable gelatinase activity by either zymography or a fluorescence-based gelatinase activity assay. The kinetic parameters of the dipeptidyl peptidase activity for glycosylated FAP were determined using dipeptide Ala-Pro-7-amino-trifluoromethyl-coumarin as the substrate. The k(cat) is 2.0 s(-1) and k(cat)/K(m) is 1.0 x 10(4) M(-1) s(-1) at pH 8.5. The pH dependence of k(cat) reveals two ionization groups with pK(a1) of 7.0 and pK(a2) of 11.0. The pH profile of k(cat)/K(m) yields similar results with pK(a1) 6.2 and pK(a2) 11.0. The neutral pK(a1) is associated with His at the active site. The basic pK(a2) might be contributed from an ionization group that is not involved directly in catalysis, instead associated with the stability of the active site structure.     

A new species of Sartidia (Graminae), endemic to ultramafic soils

A species of Sartidia De Winter, first collected by P.J. Muller in 1972 in the Cythna Letty Nature Reserve in Mpumalanga, does not match existing material of Sartidia, a genus comprising four species. The new species, S. dewinteri J. Munday & L. Fish, is most similar to S. jucunda (Schweick.) De Winter but differs in the leaf sheath colour, lower leaf blade surface texture, spikelet length and upper glume length. It differs also from all other species in the genus in the shape and branching of the inflorescence, the relative length of the lateral awns to the median awn, lemma body surface texture, callus shape and hair arrangement, palea shape and distribution. Sartidia dewinteri differs anatomically from S. angolensis and S. vanderystii in that the stereome strands in the leaf blades project partly or almost completely into the first order vascular bundles rather than not at all, and from S. jucunda by having 3 rather than 5 first order vascular bundles in the leaf. Sartidia dewinteri is known only from ultramafic soils of the Barberton Greenstone Belt and is thus considered a serpentine endemic. The IUCN conservation status of S. dewinteri is considered to be Lower Risk — least concern, although some of its ultramafic habitat is under threat from afforestation and the after effects of mining.