Keeping cell identity in Arabidopsis requires PRC1 RING-finger homologs that catalyze H2A monoubiquitination

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Highlights? AtBMI1A/B proteins prevent misexpression of embryonic traits in somatic cells ? PRC2 and AtBMI1A/B proteins maintain cells in their differentiated state ? AtBMI1A/B proteins mediate H2A monoubiquitination     

Nitrate and phosphate removal by<Emphasis Type="Italic"> Spirulina platensis</Emphasis>

The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm³ Erlenmeyer flasks under conditions of light limitation (40 mol quanta m^–2 s^–1) at a starting biomass level of 0.50 g/dm³ and varying temperature in the range 23–40°C. In this way, the best temperature for the growth of this microalga (30°C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates ( =0.044 day^–1, Q _x =33.2 mg dm^–3 day^–1) as well as volumetric rate and final yield of nitrogen removal ( =3.26 mg dm^–3 day^–1, =0.739) were obtained at 30°C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm³ vessels (mini-ponds) at the optimum temperature (30°C) but increasing the photon fluence rate to 80 mol quanta m^–2 s^–1 and varying the initial biomass concentration from 0.25 to 0.86 g/dm³. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm³ enhanced both NO₃ ^– and PO₄ ^3– removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal ( =0.032–0.050 day^–1, Q _x =34.7–42.4 mg dm^–3 day^–1, =3.24–4.06 mg dm^–3 day^–1, =0.750–0.879, =0.312–0.623 mg dm^–3 day^–1, and =0.224–0.440).     

Are respiratory enzymes the primary sources of intracellular hydrogen peroxide?

Endogenous H2O2 is believed to be a source of chronic damage in aerobic organisms. To quantify H2O2 formation, we have generated strains of Escherichia coli that lack intracellular scavenging enzymes. The H2O2 that is formed within these mutants diffuses out into the medium, where it can be measured. We sought to test the prevailing hypothesis that this H2O2 is primarily generated by the autoxidation of redox enzymes within the respiratory chain. The rate of H2O2 production increased when oxygen levels were raised, confirming that H2O2 is formed by an adventitious chemical process. However, mutants that lacked NADH dehydrogenase II and fumarate reductase, the most oxidizable components of the respiratory chain in vitro, continued to form H2O2 at normal rates. NADH dehydrogenase II did generate substantial H2O2 when it was when overproduced or quinones were absent, forcing electrons to accumulate on the enzyme. Mutants that lacked both NADH dehydrogenases respired very slowly, as expected; however, these mutants showed no diminution of H2O2 excretion, suggesting that H2O2 is primarily formed by a source outside the respiratory chain. That source has not yet been identified. In respiring cells the rate of H2O2 production was approximately 0.5% the rate of total oxygen consumption, with only modest changes when cells used different carbon sources.     

Does a High‐protein Diet Improve Weight Loss in Overweight and Obese Children?

Objective: To evaluate the effect of a high‐protein diet on anthropometry, body composition, subjective appetite, and mood sensations in overweight and obese children attending a residential weight‐loss camp. Research Methods and Procedures: Children (120; BMI, 33.1 ± 5.5 kg/m²; age, 14.2 ± 1.9 years) were randomly assigned to either a standard or high‐protein diet group (15% vs. 22.5% protein, respectively). All children were assessed at baseline and at the end of the camp for anthropometry, body composition, blood pressure, biochemical variables (n = 27), and subjective appetite and mood sensations (n = 50). Results: Attendance at the weight‐loss camp resulted in significant improvements in most measures. Campers lost 5.5 ± 2.9 kg in body weight (p < 0.001) and 3.8 ± 5.4 kg in fat mass (p < 0.001) and reduced their BMI standard deviation score by 0.27 ± 0.1 (p < 0.001) and their waist circumference by 6.6 ± 2.8 cm (p < 0.001). Subjective sensations of hunger increased significantly over the camp duration, but no other changes in appetite or mood were observed. There were no significant differences between the two diets on any physical or subjective measures. Discussion: Weight‐loss camps are effective in assisting children to lose weight and improve on a range of health outcomes, independently of the protein content of the diet. The implications of an increase in hunger associated with weight loss needs to be considered. Further work is warranted to investigate whether higher levels of dietary protein are feasible or effective in longer‐term weight‐loss interventions of this type.     

Environmental conditions and herbivore biomass determine coral reef benthic community composition: implications for quantitative baselines

Coral Reefs - Our ability to understand natural constraints on coral reef benthic communities requires quantitative assessment of the relative strengths of abiotic and biotic processes across large...     

In vitro callus induction from adult tissues of peach (Prunus persica L. Batsch)

We describe an efficient protocol for callus induction from adult tissues of Prunus persica (L.) Batsch. Three different commercial peach genotypes, Early May®, Zise May®, and UFO-3®, plus three other genotypes from hybrid crosses performed in February 2006, PS108, PS208, and PS708, were used in the study. Thirteen explant treatments were tested using nine different plant parts. Murashige and Skoog and woody plant medium salts were assayed with several concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin (KN), and thidiazuron, and two different photoperiods were tested, a 16-h photoperiod or continuous darkness. In terms of the quantitative response, two parameters were assessed: the number of d to callus induction and relative callus growth recorded after 30 d. Woody plant medium supplemented with 2,4-D and KN significantly increased the rates of callus induction in the majority of treatments. And no significant differences among the P. persica genotypes were found. The explants derived from stem and calyx produced up to 85 and 96% callus induction, respectively. The protocol described here could be used for efficient callus induction in a range of Prunus spp.     

alpha-Crystallin facilitates the reactivation of hydrogen peroxide-inactivated rhodanese

It was previously shown that rhodanese, inactivated with hydrogen peroxide, could only be reactivated in the presence of a reductant or the substrate thiosulfate if these reagents were added soon after inactivation and if the oxidant was removed. Here, we report on the facilitated reactivation (75%) of hydrogen peroxide-inactivated rhodanese by the chaperone alpha-crystallin. Reactivation by the chaperone still required a reductant and thiosulfate. Without alpha-crystallin, but in the presence of the reductant and thiosulfate, the inactivated enzyme regained about 39% of its original activity. The alpha-crystallin-assisted reactivation of hydrogen peroxide-inactivated rhodanese was independent of ATP. Further, we found, that alpha-crystallin interacted transiently, but could not form a stable complex with hydrogen peroxide-inactivated rhodanese. Unlike in prior studies that involved denaturation of rhodanese through chemical or thermal means, we have clearly shown that alpha-crystallin can function as a molecular chaperone in the reactivation of an oxidatively inactivated protein.     

APP Is Cleaved by Bace1 in Pre-Synaptic Vesicles and Establishes a Pre-Synaptic Interactome,via Its Intracellular Domain,with Molecular Complexes that Regulate Pre-Synaptic Vesicles Functions

Amyloid Precursor Protein (APP) is a type I membrane protein that undergoes extensive processing by secretases, including BACE1. Although mutations in APP and genes that regulate processing of APP, such as PSENs and BRI2/ITM2B, cause dementias, the normal function of APP in synaptic transmission, synaptic plasticity and memory formation is poorly understood. To grasp the biochemical mechanisms underlying the function of APP in the central nervous system, it is important to first define the sub-cellular localization of APP in synapses and the synaptic interactome of APP. Using biochemical and electron microscopy approaches, we have found that APP is localized in pre-synaptic vesicles, where it is processed by Bace1. By means of a proteomic approach, we have characterized the synaptic interactome of the APP intracellular domain. We focused on this region of APP because in vivo data underline the central funtional and pathological role of the intracellular domain of APP. Consistent with the expression of APP in pre-synaptic vesicles, the synaptic APP intracellular domain interactome is predominantly constituted by pre-synaptic, rather than post-synaptic, proteins. This pre-synaptic interactome of the APP intracellular domain includes proteins expressed on pre-synaptic vesicles such as the vesicular SNARE Vamp2/Vamp1 and the Ca²⁺ sensors Synaptotagmin-1/Synaptotagmin-2, and non-vesicular pre-synaptic proteins that regulate exocytosis, endocytosis and recycling of pre-synaptic vesicles, such as target-membrane-SNAREs (Syntaxin-1b, Syntaxin-1a, Snap25 and Snap47), Munc-18, Nsf, α/β/γ-Snaps and complexin. These data are consistent with a functional role for APP, via its carboxyl-terminal domain, in exocytosis, endocytosis and/or recycling of pre-synaptic vesicles.