Adventitious bud development and regeneration in Tillandsia eizii

Summary The bromeliad Tillandsia eizii is a stricking species with large, colorful, and persistent inflorescences that can reach 1 m in length. The value of this plant as an ornamental and its importance in cultural and religious activities has led to its overcollection in the wild. Clonal propagation via tissue culture may be a means to repopulate native stands while meeting the demands for this species as an ornamental and ceremonial plant. Adventitious bud proliferation was induced from axenically germinated scedling material. Parameters evaluated were the age of explant material at the time of transfer onto bud-induction medium, the concentration of plant growth regulators, and the period of exposure to induction medium. Light and seanning electron microscopy (SEM) established the origin and development of buds. Twelve-week-old seedling explants rapidly initiated adventitious buds after a 30-d induction period on shoot-initiation medium. Adventitious buds were induced in 40% of the explants placed on media with 2 mg l⁻¹ 6-benzylaminopurine (BA) (8.88 μM) plus 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA) (0.54 μM) with some cultures becoming highly prolific after repeated subeulture. Shoots elongated in proliferating cultures, and plants were successfully acclimatized and planted into the greenhouse. The results indicate that tissue culture may be used as a means to propagate this epiphytic bromeliad species, which is being seriously affected by deforestation and habitat destruction. In addition, adventitious bud proliferation can provide a means to propagate superior genotypes.     

The In Vitro and In Vivo Inhibitory Effects of Some Sulfonamide Derivatives on Rainbow Trout (Oncorhynchus Mykiss) Erythrocyte Carbonic Anhydrase Activity

The in vitro and in vivo inhibitory effects of 5-(3α, 12α-dihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (1), 5-(3α, 7α, 12α-trihydroxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (2), 5-(3α, 7α, 12α-triacetoxy-5-β-cholanamido)-1,3,4-thiadiazole-2-sulfonamide (3) and acetazolamide on rainbow trout (Oncorhynchus mykiss) (RT) erythrocyte carbonic anhydrase (CA) were investigated. The RT erythrocyte CA was obtained by affinity chromatography with a yield of 20.9%, a specific activity of 422.5?EU/mg protein and a purification of 222.4-fold. The purity of the enzyme was confirmed by SDS-PAGE. Inhibitory effects of the sulfonamides and acetazolamide on the RT erythrocyte CA were determined using the CO₂-Hydratase method in vitro and in vivo studies. From in vitro studies, it was found that all the compounds inhibited CA. The obtained I₅₀ value for the sulfonamides (1), (2) and (3) and acetazolamide were 0.83, 0.049, 0.82 and 0.052?μM, respectively. From in vivo studies, it was observed that CA was inhibited by the sulfonamides (1), (2) and (3) and acetazolamide.     

Structural and biochemical characterization of the salicylyl-acyltranferase SsfX3 from a tetracycline biosynthetic pathway

SsfX3 is a GDSL family acyltransferase that transfers salicylate to the C-4 hydroxyl of a tetracycline intermediate in the penultimate step during biosynthesis of the anticancer natural product SF2575. The C-4 salicylate takes the place of the more common C-4 dimethylamine functionality, making SsfX3 the first acyltransferase identified to act on a tetracycline substrate. The crystal structure of SsfX3 was determined at 2.5 Å, revealing two distinct domains as follows: an N-terminal β-sandwich domain that resembles a carbohydrate-binding module, and a C-terminal catalytic domain that contains the atypical α/β-hydrolase fold found in the GDSL hydrolase family of enzymes. The active site lies at one end of a large open binding pocket, which is spatially defined by structural elements from both the N- and C-terminal domains. Mutational analysis in the putative substrate binding pocket identified residues from both domains that are important for binding the acyl donor and acceptor. Furthermore, removal of the N-terminal carbohydrate-binding module-like domain rendered the stand-alone α/β-hydrolase domain inactive. The additional noncatalytic module is therefore proposed to be required to define the binding pocket and provide sufficient interactions with the spatially extended tetracyclic substrate. SsfX3 was also demonstrated to accept a variety of non-native acyl groups. This relaxed substrate specificity toward the acyl donor allowed the chemoenzymatic biosynthesis of C-4-modified analogs of the immediate precursor to the bioactive SF2575; these were used to assay the structure activity relationships at the C-4 position.     

Avian influenza viruses infect primary human bronchial epithelial cells unconstrained by sialic acid α2,3 residues

Avian influenza viruses (AIV) are an important emerging threat to public health. It is thought that sialic acid (sia) receptors are barriers in cross-species transmission where the binding preferences of AIV and human influenza viruses are sias α2,3 versus α2,6, respectively. In this study, we show that a normal fully differentiated, primary human bronchial epithelial cell model is readily infected by low pathogenic H5N1, H5N2 and H5N3 AIV, which primarily bind to sia α2,3 moieties, and replicate in these cells independent of specific sias on the cell surface. NHBE cells treated with neuraminidase prior to infection are infected by AIV despite removal of sia α2,3 moieties. Following AIV infection, higher levels of IP-10 and RANTES are secreted compared to human influenza virus infection, indicating differential chemokine expression patterns, a feature that may contribute to differences in disease pathogenesis between avian and human influenza virus infections in humans.     

Evidence for multiple molecular weight forms of somatostatin-like material in Escherichia coli

Extracts of Escherichia coli grown in defined medium contain somatostatin-related material (1-10 pg/g wet weight of cells). Preconditioned medium had no immunoactive somatostatin whereas, conditioned medium had 110-150 pg/l. Following purification of the extracted material on Sep-pak C18, Bio-Gel P-6 and HPLC, multiple molecular weight forms of somatostatin- (SRIF-) related material were identified. The material in one peak reacted in both the N-terminal and C-terminal SRIF immunoassay and coeluted on HPLC with SRIF-28, whereas that in a second peak eluted near SRIF-14 and was reactive only in the C-terminal SRIF assay. The two peaks are thus similar to SRIF-28 and SRIF-14 of vertebrates. These findings add support to the suggestion that vertebrate-type peptide hormones and neuropeptides have early evolutionary origins.     

Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.      

The mitogenome of Onchocerca volvulus from the Brazilian Amazonia focus

We report here the first complete mitochondria genome of Onchocerca volvulus from a focus outside of Africa. An O. volvulus mitogenome from the Brazilian Amazonia focus was obtained using a combination of high-throughput and Sanger sequencing technologies. Comparisons made between this mitochondrial genome and publicly available mitochondrial sequences identified 46 variant nucleotide positions and suggested that our Brazilian mitogenome is more closely related to Cameroon-origin mitochondria than West African-origin mitochondria. As well as providing insights into the origins of Latin American onchocerciasis, the Brazilian Amazonia focus mitogenome may also have value as an epidemiological resource.     

Long-term landscape changes in vegetation structure: fire management in the wetlands of KwaMbonambi,South Africa

In wetlands the effects of fire on vegetation dynamics are somewhat uncertain. A change detection analysis in the herbaceous wetlands of KwaMbonambi, South Africa, which were subject to frequent fires, revealed that in 1937 the study area comprised grassland (69%), herbaceous wetland (25%), indigenous swamp forest (4%) and tree plantations (1%). However, by 1970, tree plantations occupied 78% of the landscape and grasslands and herbaceous wetlands had declined to 9% and 6%, respectively, whereas indigenous swamp forest had increased to 6%. By 2009 tree plantations had been removed from the wetland areas. Despite this opportunity for herbaceous wetlands to recover their historical extent, they decreased to only 2%, mostly changing to indigenous swamp forest or to an herbaceous/fern (Stenochlaena tenuifolia)/woodland mosaic. Fire records showed suppression of fire to be an important contributing factor, particularly in wetlands that had been disturbed by tree plantations, although subsequently removed. A pilot burning experiment revealed that S. tenuifolia did not inhibit fire. It is therefore practicable to increase fire frequency to prevent the mosaic developing into forest. A conceptual model of the influence of fire regime on wetland vegetation type is presented and priorities for further research on wetlands and fire are recommended.