Establishment of transformed root cultures of Perezia cuernavacana producing the sesquiterpene quinone perezone

Summary The sesquiterpene quinone currently known as perezone is abundantly produced by the roots of Perezia cuernavacana. This compound is of biotechnological interest since it may be used as a pigment and has several pharmacological properties. In this work we demonstrate that perezone is also produced in transformed root cultures of P. cuernavacana. Hairy roots were induced by inoculation of internodal segments of sterile plants of P. cuernavacana with Agrobacterium rhizogenes AR12 strain. The axenic liquid MS medium cultures of the hairy roots isolated from the internodes showed active growth in the absence of growth regulators. The transformed nature of the tissue was confirmed by genomic integration (PCR and slot blot hybridization) and expression (enzyme activity) of the marker gus-gene. The production of perezone by a transformed root culture was evidenced by IR spectroscopy. Our results offer an alternative for enhanced production of perezone and represent an advantage over its extraction from natural plant populations which present problems in their agronomic culture.     

Narthecium ossifragum Associated Photosensitization in Sheep in The Faroe Islands

Hepatogenous photosensitization in sheep is an important problem in various parts of the world. Most photosensitization diseases are associated with ingestion of plant or fungal toxins. The lily, Narthecium ossifragum, has long been associated with photosensitization in lambs in western Norway (Ender 1955, Flåøyen 1993) and in the northern regions of the British Isles (Ford 1964).     

The Saccharomyces cerevisiae SGE1 gene product: a novel drug-resistance protein within the major facilitator superfamily

Several pleiotropic drug sensitivities have been described in yeast. Some involve the loss of putative drug efflux pumps analogous to mammalian P-glycoproteins, others are caused by defects in sterol synthesis resulting in higher plasma membrane permeability. We have constructed a Saccharomyces cerevisiae strain that exhibits a strong crystal violet-sensitive phenotype. By selecting cells of the supersensitive strain for normal sensitivity after transformation with a wild-type yeast genomic library, a complementing 10-kb DNA fragment was isolated, a 3.4-kb subfragment of which was sufficient for complementation. DNA sequence analysis revealed that the complementing fragment comprised the recently sequenced SGE1 gene, a partial multicopy suppressor of gal11 mutations. The supersensitive strain was found to be a sge1 null mutant. Overexpression of SGE1 on a high-copy-number plasmid increased the resistance of the supersensitive strain. Disruption of SGE1 in a wild-type strain increased the sensitivity of the strain. These features of the SGE1 phenotype, as well as sequence homologies of SGE1 at the amino acid level, confirm that the Sge1 protein is a member of the drug-resistance protein family within the major facilitator superfamily (MFS).     

Purification,and characterization of a β-mannanase of Trichoderma reesei C-30

Trichoderma reesei was studied for its ability to produce -mannanase activity on a variety of carbon sources. The highest -mannanase activity was produced on cellulose, whereas -mannan-containing carbon sources (such as kojac powder or locust bean gum) gave lower enzyme titres. The enzyme responsible for the major -mannanolytic activity from T. reesei was purified to physical homogeneity by preparative chromatofocusing and anion exchange fast protein liquid chromatography. This -mannanase is a glycoprotein, with a molecular mass of 46 (±2) kDa and an isoelectric point of 5.2. It has an optimal pH at 5.0 and broad pH stability (2.5–7.0). It is stable for 60 min at 55° C, and has an optimal temperature for activity at 75° C. During incubation with locust bean gum, the enzyme releases mainly tri- and disaccharides. Correspondence to: C. P. Kubicek     

The human complement component C8B gene: structure and phylogenetic relationship

The eighth component of human complement (C8) is a serum protein that consists of three chains (, and ), encoded by three separate genes, viz., C8A, C8B, and C8G. In serum, the -subunit is non-covalently bound to the disulfide-linked - subunit. Using a full-length C8 cDNA probe, we isolated several clones from human genomic DNA libraries. Four clones covering the complete cDNA sequence were characterized by TaqI restriction mapping and were shotgun subcloned into M13. C8-cDNA-positive clones were partially sequenced to characterize the 12 exons of the gene with sizes from 69 to 347 bp. All intron-exon junctions followed the GT-AG rule. By using polymerase chain reaction (PCR) primers located in the adjacent intron sequences, all 12 exons of the C8B gene could be amplified from genomic DNA. All fragments showed the expected sizes. The sizes of eight introns could be determined by using primer pairs that amplified two exons and the enclosed intron, and by restriction mapping. These analyses and the insert sizes of the genomic clones indicate that the C8B gene has a total size of approximately 40 kb. The polymorphic TaqI site of the C8B gene localized in intron 11 could be demonstrated by direct restriction fragment analysis of a PCR fragment containing exons 11 and 12, and the enclosed intron 11. Homology comparison of the C8B gene with C8A and C9 on the basis of the exon structure confirmed the ancestral relationship known from the protein level.     

Coexisting mangrove-coral habitat use by reef fishes in the Caribbean

We conducted visual fish surveys in coexisting mangrove-coral (CMC) habitats in Panama to analyze the effect of coral presence in mangrove habitats on the fish assemblage. Our study revealed that CMC habitats harbor distinct fish assemblages compared to mangrove habitats without coral, with greater species richness and increased herbivore abundance. Abstract in Spanish is available with online material.     

RECURRENT FORMATION AND POLYPHYLY OF NORDIC POLYPLOIDS IN DRABA (BRASSICACEAE)

Draba (Brassicaceae) is well known for its taxonomic complexity in arctic and alpine floras, and the polyploids in particular present vexing taxonomic problems. It has been suggested that polyploids in Draba may have formed recurrently from different populations of the parental species (polytopy), and it is also possible that a given taxonomic species may actually comprise several polyploid races, each originating from different progenitor species (polyphyly). To unravel the taxonomic complexity of polyploid Draba in the Nordic area, we investigated three of the most morphologically variable species and their possible progenitors using enzyme electrophoresis and restriction site analysis of chloroplast DNA (cpDNA) and nuclear ribosomal RNA genes (rDNA): D. norvegica (6x), D. lactea (6x), and D. corymbosa (16x). Electrophoretic analyses of progeny showed high levels of fixed heterozygosity in all three polyploids, demonstrating that all are genetic alloploids. Electrophoretic and rDNA data indicate that polytopic and/or polyphyletic origins have contributed to the complexity of these polyploids. However, a lack of cpDNA variation among the species limited the usefulness of this molecule for analysis of polyploid origins. The considerable electrophoretic variation observed in D. norvegica necessitates a minimum of three and probably 13 independent origins. Electrophoretic and rDNA data suggest that D. lactea and D. corymbosa are polyphyletic polyploids. Crossing data also support that D. corymbosa is polyphyletic. Given the widespread geographic distributions of these species and their possible progenitors, and that the populations analyzed represent only a small fraction of their geographic distributions, it is likely that these species have formed numerous times in different areas. As more molecular analyses of polyploids are completed, the data continue to suggest that multiple origins of polyploids are the rule rather than the exception.     

Rhizobium extracellular structures in the symbiosis

The extracellular and surface polysaccharides produced by Rhizobium species constitute a composite macromolecular interface between the bacterial cell and its environment. Several of these polysaccharides are involved in the complex series of interactions leading to the establishment of an effective Rhizobium-legume symbiosis. Extracellular heteropolysaccharides (EPSs) are found in culture supernatants, while capsular polysaccharides adhere to the cell surface. Cyclic (1–2)--d glucan is a periplasmic oligosaccharide that has also been found in the culture supernatants of some strains. The lipopolysaccharides (LPSs), which form part of the outer membrane and contain the O-somatic antigens, comprise the other major group of extracellular polysaccharides. In this review we will describe the major Rhizobium extracellular structures and their role in symbiosis with leguminous plants.The authors are with the Departamento de Microbiologia y Parasitologia, Facultad de Farmacia. Universidad de Sevilla, 41012 Sevilla, Spain     

A simple model of human foveal ganglion cell responses to hyperacuity stimuli

We developed a physiologically plausible model of the first steps of spatial visual information processing in the fovea of the human retina. With the predictions of this model we could support the hypothesis that, for moderate contrasts ( 40%), hyperacuity is mediated by the magnocellular (MC-) pathway. Despite the lower sampling density in the MC pathway, as compared to the parvocellular (PC-) pathway, the information that is transferred by the MC ganglion cells is sufficient to achieve thresholds comparable to those of human subjects in psychophysical tasks. This is a result of the much higher signal-to-noise ratio of the MC pathway cell signals. The PC pathway cells do not transfer enough information for hyperacuity thresholds.