Ribosomal RNA sequence phylogeny is not congruent with ascospore morphology among species in Ceratocystis sensu stricto

The genus Ceratocystis sensu stricto includes important fungal pathogens of woody and herbaceous plants. This genus is distinguished from species in Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore shape has been used extensively in delineating Ceratocystis taxa, which show a large variety of ascospore shapes. Sequence analysis of one region of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA subunit showed that there was a majority of multiple substitutions at nucleotide sites and that there was a low transition/transversion ratio, T = 0.72. Both of these results suggest that these are well established, old species. Ascospore morphology, for the most part, was not congruent with the molecular phylogeny, and the use of morphological characters may be misleading in the taxonomy of these species.      

Assay of sulfotransferases.

Two methods are described for the assay of sulfotransferases which are active with sulfate acceptors bearing the hydroxyl functional group. Assays were developed for enzymes which transfer sulfate from 3′-phosphoadenosine–5′-phosphosulfate (PAPS) to sterols, phenols, and simple alcohols thereby forming the corresponding sulfate esters. With a filter binding assay, useful with crude and purified enzyme preparations, a radioactive sterol substrate is used and subsequently separated from labeled product, allowing the determination of between 50 and 400 pmol of product. In a second method, [³⁵S]PAPS is used and the labeled product is separated from PAPS and inorganic sulfate by a thin-layer technique in which product migrates close to the solvent front; the assay is useful with a broad array of substrates and is more sensitive than the filter binding assay.     

Giemsa-based cytological assessment of area,shape and nucleus:cytoplasm ratio of goblet cells of rabbit bulbar conjunctiva

Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm² (average 193 ± 50 μm²). The area could be predicted reliably from the longest and shortest dimensions (r² = 0.903). The areas of goblet cell nuclei were 15–58 μm² (average 33 ± μm²) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation.     

Cell cycle and differentiation

The development of multicellular organisms relies on the temporal and spatial control of cell proliferation and cell growth. The relationship between cell-cycle progression and development is complex and characterized by mutual dependencies. On the level of the individual cell, this interrelationship has implications for pattern formation and cell morphogenesis. On a supercellular level, this interrelationship affects meristem function and organ growth. Often, developmental signals not only direct cell-cycle progression but also set the frame for cell-cycle regulation by determining cell-type-specific cell-cycle modes. In other cases, however, cell-cycle progression appears to be required for the further differentiation of some cell types. There are also examples in which cell cycle and differentiation seem to be controlled at the same level and progress rather independently from each other or are linked by the same regulator or pathway. Furthermore, different relationships between cell cycle and differentiation can be combined in a succession of events during development, leading to complex developmental programs.     

Redox control of aryl sulfotransferase specificity

Aryl sulfotransferase IV from rat liver has the very broad substrate range that is characteristic of the enzymes of detoxication. With the conventional assay substrates, 4-nitrophenol and PAPS, sulfation was considered optimal at pH 5.5 whereas the enzyme in the physiological pH range was curiously ineffective. These properties would seem to preclude a physiological function for this cytosolic enzyme. Partial oxidation of the enzyme, however, results not only in a substantial increase in the rate of sulfation of 4-nitrophenol at physiological pH but also in a shift of the pH optimum to this range and radically altered overall substrate specificity. The mechanism for this dependence on redox environment involves oxidation at Cys66, a process previously shown to occur by formation of a mixed disulfide with glutathione or by the formation of an internal disulfide with Cys232. Oxidation at Cys66 acts only as a molecular redox switch and is not directly part of the catalytic mechanism. Underlying the activation process is a change in the nature of the ternary complex formed between enzyme, phenol, and the reaction product, adenosine 3',5'-bisphosphate. The reduced enzyme gives rise to an inhibitory, dead-end ternary complex, the stability of which is dictated by the ionization of the specific phenol substrate. Ternary complex formation impedes the binding of PAPS that is necessary to initiate a further round of the reaction and is manifest as profound, substrate-dependent inhibition. In contrast, the ternary complex formed when the enzyme is in the partially oxidized state allows binding of PAPS and the unhindered completion of the reaction cycle.     

What's in a name; Genetic structure in Solanum section Petota studied using population-genetic tools

Background  

The taxonomy and systematic relationships among species of Solanum section Petota are complicated and the section seems overclassified. Many of the presumed (sub)species from South America are very similar and they are able to exchange genetic material. We applied a population genetic approach to evaluate support for subgroups within this material, using AFLP data. Our approach is based on the following assumptions: (i) accessions that may exchange genetic material can be analyzed as if they are part of one gene pool, and (ii) genetic differentiation among species is expected to be higher than within species.     

Synergizing metabolic flux analysis and nucleotide sugar metabolism to understand the control of glycosylation of recombinant protein in CHO cells

Background

The photorespiratory nitrogen cycle in C₃ plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO₂. Because of the loss of CO₂ and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C₃ plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.

Results

When grown in ambient air, but not in elevated CO₂, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.

Conclusions

Tobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars.     

Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

Climate change alters elevational phenology patterns of the European spruce bark beetle (Ips typographus)

The European spruce bark beetle Ips typographus is the most important insect pest in Central European forests. Under climate change, its phenology is presumed to be changing and mass infestations becoming more likely. While several studies have investigated climate effects across a latitudinal gradient, it remains an open question how phenology will change depending on elevation and topology. Knowing how an altered climate is likely to affect bark beetle populations, particularly across diverse topographies and elevations, is essential for adaptive management. We developed a time‐varying distributed delay model to predict the phenology of I. typographus. This approach has the particular advantage of capturing the variability within populations and thus representing its stage structure at any time. The model is applied for three regional climate change scenarios, A1B, A2 and RCP3PD, to the diverse topography of Switzerland, covering a large range of elevations, aspects and slopes. We found a strong negative relationship between voltinism and elevation. Under climate change, the model predicts an increasing number of generations over the whole elevational gradient, which will be more pronounced at low elevations. In contrast, the pre‐shift in spring swarming is expected to be greater at higher elevations. In comparison, the general trend of faster beetle development on steep southern slopes is only of minor importance. Overall, the maximum elevation allowing a complete yearly generation will move upwards. Generally, the predicted increase in number of generations, earlier spring swarming, more aggregated swarming, together with a projected increase in drought and storm events, will result in a higher risk of mass infestations. This will increase the pressure on spruce stands particularly in the lowlands and require intensified management efforts. It calls for adapted long‐term silvicultural strategies to mitigate the loss of ecosystem services such as timber production protection against rockfall and avalanches and carbon storage.