Sigma factor is not released during transcription in Bacillus subtilis

Molecular Genetics and Genomics - The relationship between sigma (σ) and delta (δ) factors of Bacillus subtilis RNA polymerase has been analyzed during initiation of RNA synthesis. When...     

Induction by ouabain of hemoglobin synthesis in cultured friend erythroleukemic cells

Induction of erythroid differentiation in ouabain-resistant murine erythroleukemia cells by ouabain is reported. Ouabain induction results in the appearance of hemoglobin-containing cells 12–24 hr earlier than induction of the same clone by dimethyl sulfoxide. The levels of globin mRNA after ouabain induction are similar in amount to the globin mRNA levels observed after induction by dimethyl sulfoxide. The concentration of ouabain required to induce hemoglobin synthesis depends upon the K⁺ ion levels in the culture medium. Lowering the extracellular K⁺ ion concentration 2–4 fold reduced by 10–40 fold the ouabain concentration necessary for the induction of hemoglobin synthesis. In low K⁺ medium (1.8 mM), ouabain is an effective inducer of hemoglobin synthesis at a concentration of 0.02 mM. This K⁺ effect is specific for ouabain induction, since induction by other inducers, such as dimethyl sulfoxide and dimethyl acetamide, does not exhibit this marked sensitivity to the levels of K⁺ ions in the culture medium. These results suggest that the binding of ouabain to the plasma membrane enzyme, $\text{Na}\text{K}$ ATPase, is required for the induction of erythroid differentiation by ouabain. A small but significant proportion of wild-type, ouabain-sensitive cells also can be induced by ouabain, below ouabain concentrations that are toxic to these cells. The observation that the binding of ouabain to the $\text{Na}\text{K}$ ATPase induces hemoglobin synthesis suggests that changes in the intracellular concentration of K⁺ ions may be involved in the control of erythroid differentiation in Friend erythroleukemic cells.     

Ethylene and IAA transport in potato

Although elongation growth is reduced by ethylene, swelling responses do not occur. Ethylene reduces neither transport nor metabolism of applied IAA in either mesocotyl or coleoptile. We propose that maintenance of high auxin levels within these tissues sustains polar transport and contributes to the relative insensitivity of maize to applied ethylene.     

The zinc,copper, and manganese status of children with malabsorption syndromes and inborn errors of metabolism

The zinc, copper, and manganese status of seven children with malabsorption syndromes of varied etiology (MVE) and 12 with inborn errors of metabolism (IEM) receiving semi-synthetic diets was investigated using serum and hair trace element concentrations, dietary trace element intakes, and anthropometric measurements as the principal indices. The hair zinc levels of both test groups and hair manganese levels of the IEM group were significantly lower (p<0.05) than those of their respective healthy controls matched by age, sex, and geographic location, despite comparable dietary zinc and manganese intakes in test and control subjects. Four subjects from the malabsorption and five from the inborn errors group had hair zinc levels below 100 μg/g (range 30–88 μg/g). Of these nine subjects, serum zinc levels were determined for six, and five were less than normal (range 64–74 μg/dL). In contrast, the copper status of the MVE and IEM subjects, as indicated by hair and dietary copper levels, was not lower than the controls. Mean serum copper levels were 136±30 and 171±40 μg/dL for the IEM and MVE groups, respectively. Levels for the MVE subjects were higher than published normal values. The suboptimal zinc and manganese status observed in some of these test subjects probably arose from malabsorption and decreased availability of dietary zinc and manganese. However, the zinc depletion was not severe enough to result in linear growth retardation.     

Century‐long apparent decrease in intrinsic water‐use efficiency with no evidence of progressive nutrient limitation in African tropical forests

Forests exhibit leaf‐ and ecosystem‐level responses to environmental changes. Specifically, rising carbon dioxide (CO₂) levels over the past century are expected to have increased the intrinsic water‐use efficiency (iWUE) of tropical trees while the ecosystem is gradually pushed into progressive nutrient limitation. Due to the long‐term character of these changes, however, observational datasets to validate both paradigms are limited in space and time. In this study, we used a unique herbarium record to go back nearly a century and show that despite the rise in CO₂ concentrations, iWUE has decreased in central African tropical trees in the Congo Basin. Although we find evidence that points to leaf‐level adaptation to increasing CO₂—that is, increasing photosynthesis‐related nutrients and decreasing maximum stomatal conductance, a decrease in leaf δ¹³C clearly indicates a decreasing iWUE over time. Additionally, the stoichiometric carbon to nitrogen and nitrogen to phosphorus ratios in the leaves show no sign of progressive nutrient limitation as they have remained constant since 1938, which suggests that nutrients have not increasingly limited productivity in this biome. Altogether, the data suggest that other environmental factors, such as increasing temperature, might have negatively affected net photosynthesis and consequently downregulated the iWUE. Results from this study reveal that the second largest tropical forest on Earth has responded differently to recent environmental changes than expected, highlighting the need for further on‐ground monitoring in the Congo Basin.     

Prior evolution in stochastic versus constant temperatures affects RNA virus evolvability at a thermal extreme

It is unclear how historical adaptation versus maladaptation in a prior environment affects population evolvability in a novel habitat. Prior work showed that vesicular stomatitis virus (VSV) populations evolved at constant 37°C improved in cellular infection at both 29°C and 37°C; in contrast, those evolved under random changing temperatures between 29°C and 37°C failed to improve. Here, we tested whether prior evolution affected the rate of adaptation at the thermal‐niche edge: 40°C. After 40 virus generations in the new environment, we observed that populations historically evolved at random temperatures showed greater adaptability. Deep sequencing revealed that most of the newly evolved mutations were de novo. Also, two novel evolved mutations in the VSV glycoprotein and replicase genes tended to co‐occur in the populations previously evolved at constant 37°C, whereas this parallelism was not seen in populations with prior random temperature evolution. These results suggest that prior adaptation under constant versus random temperatures constrained the mutation landscape that could improve fitness in the novel 40°C environment, perhaps owing to differing epistatic effects of new mutations entering genetic architectures that earlier diverged. We concluded that RNA viruses maladapted to their previous environment could “leapfrog” over counterparts of higher fitness, to achieve faster adaptability in a novel environment.     

Reproductives and eggs trigger worker vibration in a subterranean termite

In insect societies, the presence of reproductives or eggs has been shown to shape several biological traits in the colony members. Social interactions are one of these traits that involve modification of the communication system of the entire colony. Many studies described the role of chemical compounds and dominance behaviors in the presence of reproductive but vibratory behaviors received very few investigations. Yet, vibratory behaviors are ideal candidates, particularly for subterranean species like termites, as they could be quickly transmitted through the substrate and could be very diversified (origin, modulation). Here, we investigated whether the presence of reproductives/eggs affects the vibratory behavior (body‐shaking) of workers in the subterranean termite Reticulitermes flavipes. Our results reveal that the presence of reproductives or eggs triggers an increase of workers' body‐shaking, independent of their colony of origin after 24 hr. We hypothesize that vibratory communication could be used to transfer information about the presence of reproductives and eggs to the entire colony, suggesting that vibratory behaviors could serve as an important yet neglected mediator of social regulation.     

First characterization of congenital myasthenic syndrome type 5 in North Africa

Molecular Biology Reports - Congenital myasthenic syndromes (CMS) are associated with defects in the structure and the function of neuromuscular junctions. These rare disorders can result from...