Global analysis of ecological niche conservation and niche shift in exotic populations of monkeyflowers (Mimulus guttatus,M. luteus) and their hybrid (M. × robertsii)

ABSTRACT

Background

Hybridisation associated with biological invasions may generate new phenotypic combinations, allowing hybrids to occupy new ecological niches. To date, few studies have assessed niche shifts associated with hybridisation in recently introduced populations while simultaneously characterising the niche of parental species in both native and introduced ranges.     

Humic Acids Interfere with Nutrient Sensing in Plants Owing to the Differential Expression of TOR

Journal of Plant Growth Regulation - The environmental consequences of industrial agriculture have increasingly called attention to new biotechnologies. The use of biostimulants based on humic...     

Über die Farbstoffbildung durchAzotobacter chroococcum

Zusammenfassung Der schwarzbraune Farbstoff vonA. chroococcum wird bei gehemmter Substratatmung gebildet. Das wurde durch stark gedrosselte Phosphorversorgung bei im übrigen optimaler Ernährung und betont guter Versorgung mit Kalium, Eisen und Kupfer erreicht.Da nur bei neutraler bis alkalischer Reaktion Farbstoff gebildet wird, was es notwendig, das Nährsubstrat ausreichend zu puffern. Es erhielt deshalb einen Zusatz von Calciumcarbonat. Geschah das nicht, dann bildeteA. chroococcum bei Phosphormangel Zuckeroxydationsprodukte, wahrscheinlich Gluconsäure neben möglicherweise noch anderen Säuren, wobei der pH-Wert bis 4 oder etwas tiefer absank. Glucuronsäure entstand in sehr geringen Mengen unter allen geprüften Ernährungsbedingungen. A. chroococcum war katalatisch aktiver alsA. agilis, ganz besonders bei Phosphormangel, vermutlich deshalb, weilA. chroococcum unter diesen Bedingungen vornehmlich über das Flavinsystem atmete und dabei auch mehr Wasserstoffperoxyd bildete.Der mit viel Phosphat ernährte Bakterientyp vonA. chroococcum reagierte auf verschiedene Atmungshemmstoffe empfindlicher als der Typ aus phosphatarmer Nährlösung. Auch das spricht dafür, daß der schwächer atmende, farbstoffbildende Typ über das Flavinsystem atmete und nicht über das Cytochromsystem mit den zugehörigen Phosphorylierungen, was für den phosphorreich ernährten Stoffwechseltyp zutrifft.

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On pigment production byAzotobacter chroococcum I. Culture conditions favouring pigment production

Summary The brownish black pigment ofA. chroococcum is produced during restricted respiration of the substrate. This condition was obtained by lowering drastically the phosphorus supply while the nutrition for the rest was optimal and potassium, iron, and copper were available in sufficient concentrations.Since pigment is produced only with neutral or alcaline reaction it was necessary to buffer the culture medium sufficiently. For this purpose calcium carbonate was added. Without buffering A. chroococcum when lacking phosphorus formed products of sugar oxidation, probably gluconic acid and possibly other acids, too, while the pH-value declined to 4 or somewhat below. Glucuronic acid was produced in very small quantities at any nutritional condition checked. A. chroococcum was more active in catalase thanA. agilis, especially with lack of phosphorus. This is supposed to be due to the fact that under such conditions the flavine system producing higher quantities of hydrogen peroxide is primarily active in respiration ofA. chroococcum.The type ofA. chroococcum grown in a medium rich in phosphorus was more susceptible to various inhibitors of respiration than was the other type grown in a medium lacking phosphorus. This also points to the fact that the more weakly respiring and pigment-producing type acts by the flavine system and not by the cytochrome system using phosphorylations as does the metabolic type developing with abundant supply of phosphorus.

     

A Cytoplasmic New Catalytic Subunit of Calcineurin in Trypanosoma cruzi and Its Molecular and Functional Characterization

Parasitological cure for Chagas disease is considered extremely difficult to achieve because of the lack of effective chemotherapeutic agents against Trypanosoma cruzi at different stages of infection. There are currently only two drugs available. These have several limitations and can produce serious side effects. Thus, new chemotherapeutic targets are much sought after. Among T. cruzi components involved in key processes such as parasite proliferation and host cell invasion, Ca²⁺-dependent molecules play an important role. Calcineurin (CaN) is one such molecule. In this study, we cloned a new isoform of the gene coding for CL strain catalytic subunit CaNA (TcCaNA2) and characterized it molecularly and functionally. There is one copy of the TcCaNA2 gene per haploid genome. It is constitutively transcribed in all T. cruzi developmental forms and is localized predominantly in the cytosol. In the parasite, TcCaNA2 is associated with CaNB. The recombinant protein TcCaNA2 has phosphatase activity that is enhanced by Mn²⁺/Ni²⁺. The participation of TcCaNA2 in target cell invasion by metacyclic trypomastigotes was also demonstrated. Metacyclic forms with reduced TcCaNA2 expression following treatment with morpholino antisense oligonucleotides targeted to TcCaNA2 invaded HeLa cells at a lower rate than control parasites treated with morpholino sense oligonucleotides. Similarly, the decreased expression of TcCaNA2 following treatment with antisense morpholino oligonucleotides partially affected the replication of epimastigotes, although to a lesser extent than the decrease in expression following treatment with calcineurin inhibitors. Our findings suggest that the calcineurin activities of TcCaNA2/CaNB and TcCaNA/CaNB, which have distinct cellular localizations (the cytoplasm and the nucleus, respectively), may play a critical role at different stages of T. cruzi development, the former in host cell invasion and the latter in parasite multiplication.     

Infectivity of Rhizobium meliloti as affected by extracellular polysaccharides

O livares , J., B edmar , E.J. & M artinez -M olina , E. 1984. Infectivity of Rhizobium meliloti as affected by extracellular polysaccharides. Journal of Applied Bacteriology 56 , 389–393.
The addition of crude extracellular polysaccharide (EPS) preparations from highly infective Rhizobium meliloti increased the infectivity of a poorly infective strain. The addition of crude EPS preparations from another species did not promote nodu-lation, suggesting the specificity of such an effect. Acid treatment of the crude EPS preparations resulted in total inhibition of nodulation.     

Effect of chemical inhibitors of photorespiration on nitrogenase activity in nodulated alfalfa plants

Nitrogen fixation (measured as acetylene reduction) by whole nodulated alfalfa plants was stimulated when the plants were treated with isonicotinic acid hydracide (INH) and glyoxylate, both inhibitors of the glycolate pathway of carbohydrate metabolism, at concentrations of 300 and 100 mM, respectively. Reducing energetic loses caused by photorespiration results in an increase in the symbiotic nitrogen fixation.Abbreviation INH isonicotinic acid hydracide     

The interaction of the histone H1-related protein phi 0 with chromatin

Protein phi 0 is a unique protein which is present in the sperm of the sea cucumber, Holothuria tubulosa. It associates with histones, but its physiological role is unknown. From its amino acid composition and sequence, protein phi 0 can be considered as an H1-related protein. In this paper, we have studied its interaction with chicken erythrocyte chromatin particles of different complexity, from core particles to polynucleosomes. Addition of protein phi 0 results in marked chromatin insolubilization. The higher the molecular weight of the chromatin fragment, the lower is the phi 0/nucleosome molar ratio at which precipitation occurs, so that complete insolubilization of polynucleosomes is achieved at a phi 0/nucleosome molar ratio which is identical to that found in mature H. tubulosa spermatozoa. We have also found that the interaction of protein phi 0 with chromatin is cooperative. These findings contribute to clarification of the peculiar physico-chemical properties shown by H. tubulosa sperm chromatin and the role played by the phi 0 protein.     

Sequence of ISRm4 from Rhizobium meliloti strain GR4.

ISRm4, an IS-like sequence structurally similar to Pseudomonas cepacia insertion element IS402, was identified by sequence analysis. This 933-bp element carries 17-bp putative terminal inverted repeats with five mismatches and a putative direct target duplication of 3 bp.     

Contrasting Phylogenetic and Diversity Patterns in Octodontoid Rodents and a New Definition of the Family Abrocomidae

Octodontoidea is the most species-rich clade among hystricomorph rodents. Based on a combined parsimony analysis of morphological and molecular data of extinct and extant species, we analyze the history of South American octodontoids and propose ages of divergence older than interpreted so far. Early Abrocomidae are recognized for the first time, and a new definition of the family is provided. Traditionally accepted fossil-based times of origin for the southern clades are reinterpreted as later stages of differentiation markedly uncoupled from the origin, differentiation implying specializations for open environments as shown in a morphospace of skull variation. Origin of crown groups is also strongly uncoupled from origin of clades as a consequence of extinction of deep lineages. In the resulting diversity pattern of modern southern clades of octodontoids, the combination of greater disparity, less content of evolutionary history, and lower taxonomic diversity, compared to their northern counterparts, appears at first counterintuitive. We propose that primary components of diversity derived from evolutionary transformation or anagenesis, on the one hand, and from cladogenesis and extinction, on the other, should not be considered associated, or at least not necessarily. Certain patterns of relationships between these distinct components could be driven by environmental dynamics. Like environments, octodontoid diversity would have been more stable in northern South America, whereas in the south, both strong adaptive change and extinction would have been triggered by emerging derived environments.