Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean

The absorption of visible light in aquatic environments has led to the common assumption that aquatic organisms sense and adapt to penetrative blue/green light wavelengths but show little or no response to the more attenuated red/far-red wavelengths. Here, we show that two marine diatom species, Phaeodactylum tricornutum and Thalassiosira pseudonana, possess a bona fide red/far-red light sensing phytochrome (DPH) that uses biliverdin as a chromophore and displays accentuated red-shifted absorbance peaks compared with other characterized plant and algal phytochromes. Exposure to both red and far-red light causes changes in gene expression in P. tricornutum, and the responses to far-red light disappear in DPH knockout cells, demonstrating that P. tricornutum DPH mediates far-red light signaling. The identification of DPH genes in diverse diatom species widely distributed along the water column further emphasizes the ecological significance of far-red light sensing, raising questions about the sources of far-red light. Our analyses indicate that, although far-red wavelengths from sunlight are only detectable at the ocean surface, chlorophyll fluorescence and Raman scattering can generate red/far-red photons in deeper layers. This study opens up novel perspectives on phytochrome-mediated far-red light signaling in the ocean and on the light sensing and adaptive capabilities of marine phototrophs.     

Growth hormone responses to continuous and intermittent exercise in females under oral contraceptive therapy

In this study we investigated the effect of oral contraceptive (OC) use (OCU) and non-use (OCNU) on growth hormone (GH) responses to exercise in the same females (n = 7, age 22-31 years) during the normal course of OC therapy. Continuous (60% maximum oxygen consumption, VO2max for 20 min) and intermittent exercise (>80% VO2max) protocols of equal total duration, and similar external work were performed during phases of OCNU (days 3-5 of the menstrual cycle) and OCU (days 7-11). Levels of GH, lactate, 17 beta-estradiol, and progesterone were measured. Lactate responses were significantly greater (P<0.05) during intermittent than continuous exercise, with no effect of OC use. However, significantly greater GH responses were found during the OCU phase than the OCNU phase in both the continuous (+94%) and intermittent (+250%) exercise protocols. Estradiol and progesterone levels increased significantly during exercise in all four conditions. We suggest that the increased GH responses observed during the OCU-phase were potentiated by the elevated levels levels of total estrogens (endogenous 17 beta-estradiol and exogenous ethinyl estradiol). It is suggested that training programs for female athletes could be timed in accordance with the menstrual cycle to benefit from an increased GH response to exercise during phases of OC use or the luteal phase of women not on OC therapy.     

An anchored restriction-mapping approach applied to the genetic analysis of the Anopheles gambiae malaria vector complex 1

We introduce here a simple approach for rapidly determining restriction maps for a number of regions of a genome; this involves "anchoring" a map with a rare restriction site (in this case the seldom-cutting EagI) followed by partial digestion of a frequent-cutting enzyme (e.g., Sau 3A). We applied this technology to five species of the Anopheles gambiae complex. In a single Southern blot we obtained about a 15-kb restriction map each for the mtDNA, rRNA gene, and a scnDNA region for each of five species. Phylogenetic analyses of these regions yield trees at odds with the more traditional chromosome inversion-based trees. The value of the approach for systematic purposes is the ease with which several large, independent regions of the genome can be quickly assayed for molecular variation.      

Inhibition of ruthenium red-induced Ca2+ efflux from liver mitochondria by the antibiotic X-537A

It has been reported (Becker, G.L., Fiskum, G. and Lehninger, A.L. (1980) J. Biol. Chem. 255, 9009-9012) that respiring rat liver mitochondria suspended in KC1 medium containing ATP, Mg2+ and phosphate, maintain a steady state extramitochondrial free Ca2+ concentration of about 0.5 microM. The results reported here show that the addition of the antibiotic X-537A, at concentrations far below those required for ionophorous activity, caused a perturbation in this steady state, lowering the extramitochondrial free Ca2+ concentration by about 0.20 microM. This shift in steady state was clarified by a study of X-537A inhibition of the Ca2+ efflux induced by ruthenium red; a half-maximum effect was observed at approximately 25 nM X-537A. No effect on Ca2+ transport through the influx uniporter was observed. The possibility of a generalized stabilizing action of the antibiotic on the mitochondrial membrane seems to be ruled out by its effectiveness at very low concentrations.     

Spatial and Temporal Variation of Plant Fragment Removal by Two Species of <Emphasis Type="Italic">Atta</Emphasis> Leaf-Cutting Ants

Leaf-cutting ants are responsible for much of living plant fragment removal in Neotropical regions, causing major damage in both in natural and agricultural systems. To understand the variation in plant fragment removal by leaf-cutting ants and the influence that temporal and spatial factors have on such variation, we evaluated plant fragments collected by two ant species, Atta laevigata and A. sexdens rubropilosa in different seasons (rainy and dry) and in different forest systems (natural area of cerrado sensu stricto and monoculture of Eucalyptus sp.) in 2014 in Goianésia, Goiás, Brazil. Heavier plant fragments were removed during the dry season and in monoculture areas; A. laevigata removed heavier fragments than A. sexdens rubropilosa. Furthermore, we observed a positive association between the weight of collected fragments and the weight of worker ants and higher weights in A. laevigata. The study shows that the weight of plant fragments removed by leaf-cutting ants is conditioned temporally and spatially, and by the ant species involved. More detailed studies of each of these factors are need to better understand the dynamics of these foraging ants and how abiotic and biotic factors affect this process.     

Adenosine signaling and adenosine deaminase regulation of immune responses: impact on the immunopathogenesis of HIV infection

Infection by human immunodeficiency virus (HIV) causes the acquired immune deficiency syndrome (AIDS), which has devastating effects on the host immune system. HIV entry into host cells and subsequent viral replication induce a proinflammatory response, hyperactivating immune cells and leading them to death, disfunction, and exhaustion. Adenosine is an immunomodulatory molecule that suppresses immune cell function to protect tissue integrity. The anti-inflammatory properties of adenosine modulate the chronic inflammation and immune activation caused by HIV. Lack of adenosine contributes to pathogenic events in HIV infection. However, immunosuppression by adenosine has its shortcomings, such as impairing the immune response, hindering the elimination of the virus and control of viral replication. By attempting to control inflammation, adenosine feeds a pathogenic cycle affecting immune cells. Deamination of adenosine by ADA (adenosine deaminase) counteracts the negative effects of adenosine in immune cells, boosting the immune response. This review comprises the connection between adenosinergic system and HIV immunopathogenesis, exploring defects in immune cell function and the role of ADA in protecting these cells against damage.     

The relationship between codon boundaries and multiple reading-frame preferences: coding organization of bacterial insertion sequences

Theoretical considerations have shown that the five possible overlapping reading-frame configurations differ significantly in their coding flexibility and thus in their information content (Siegel and Fitch 1980; Smith and Waterman 1980). Contrary to expectation, the overlapping frame configuration allowing the greatest coding flexibility is rarely seen, whereas one of the most constraining is common. We point out here that this overlapping reading-frame paradox and an observed but unexplained preference in coding regions for a pyrimidine-purine at codon boundaries (Shepherd 1981; Jones and Kafatos 1982; Smith et al. 1983) are intimately linked. The codon boundary preference, which may be related to translation efficiency or accuracy, places constraints on the evolution of overlapping coding regions. These considerations may help identify actual coding regions in DNA sequences. We have analyzed five sequenced (enteric) bacterial insertion sequences for codon boundary incidences and reading-frame configurations and find that they are consistent with these proposed constraints.      

Sterol methenyl transferase inhibitors alter the ultrastructure and function of the Leishmania amazonensis mitochondrion leading to potent growth inhibition

We describe here the effects of Delta(24(25)) sterol methenyl transferase inhibitors (SMTI) on promastigote and axenic amastigote forms of Leishmania amazonensis. When these cells were exposed to 20-piperidin-2-yl-5alpha-pregnan-3beta-20-diol (22,26-azasterol; AZA), hydrazone-imidazol-2-yl-5alpha-pregnan-3beta-ol (IMI), 20-hydrazone-pyridin-2-yl-5alpha-pregnan-3beta-ol (PYR) or 24(R,S),25-epiiminolanosterol (EIL), a concentration- and time-dependent inhibition of growth was observed, with IC(50) values in the sub-micromolar range. Ultrastructural alterations in treated cells were mainly observed in the mitochondrion, which displayed an intense swelling and a reduction of the electron density of the matrix with remarkable changes in the inner mitochondrial membranes. Mitochondrial transmembrane electric potential (DeltaPsi) was measured using spectrophotometric methods in control and treated promastigotes permeabilized with digitonin. After energization with the substrates for complexes I, II or IV of the respiratory chain, it was possible to detect marked changes of DeltaPsi in promastigotes treated with 1 microM of the SMTI for 48 or 72 h when compared with normal cells, indicating that these compounds led to the loss of the energy-transducing properties of the mitochondrial inner membrane, probably related to the alteration of its lipid composition. The present study confirms these findings, showing that in Leishmania amazonensis the mitochondrial complex appears to be the first organelle affected after treatment with different SMTI.     

Low-resolution structure,oligomerization and its role on the enzymatic activity of a sucrose-6-phosphate hydrolase from Bacillus licheniformis

Amino Acids - Knowing the key features of the structure and the biochemistry of proteins is crucial to improving enzymes of industrial interest like β-fructofuranosidase. Gene sacA from...     

Heat stress negatively affects physiology and morphology during germination of Ormosia coarctata (Fabaceae,Papilionoideae)

Research on the morphophysiological behavior of forest seeds during germination with respect to climate change is scarce. To date, there have been no studies on the biochemical or morphological aspects of Ormosia spp. In this study, we subjected Ormosia coarctata seeds to various temperature conditions to investigate temperature-dependent impacts on morphology, reactive oxygen species (ROS) generation, antioxidant systems, and storage systems. Analyses were performed on seeds exposed to 25, 35, and 40 °C for 48, 96, and 144 h. The morphology was evaluated by radiation using a Faxitron MX-20 device. ROS production (superoxide anion and hydrogen peroxide), malonaldehyde (MDA), carbonylated proteins, antioxidant enzyme activity (superoxide dismutase [SOD], ascorbate peroxidase [APX], catalase [CAT], and peroxidase [POX]), β-carotene, lycopene, glucose, and reserve enzyme activity (α- and β-amylase, lipase, and protease) were analyzed by spectrophotometry. Heat stress (40 °C) decreased germination by 76.2% and 78.1% (compared to 25 and 35 °C, respectively), caused damage to the external morphology of the seed, increased the content of ROS, MDA, and carbonylated proteins, and reduced APX, CAT, and POX activity. Furthermore, heat stress decreased glucose content and α-amylase activity. These results suggest that an increase of 5 °C in temperature negatively affects germination, promotes oxidative stress, and induces deterioration in O. coarctata seeds.