New and classic families of secreted fungal heme peroxidases

Heme-containing peroxidases secreted by fungi are a fascinating group of biocatalysts with various ecological and biotechnological implications. For example, they are involved in the biodegradation of lignocelluloses and lignins and participate in the bioconversion of other diverse recalcitrant compounds as well as in the natural turnover of humic substances and organohalogens. The current review focuses on the most recently discovered and novel types of heme-dependent peroxidases, aromatic peroxygenases (APOs), and dye-decolorizing peroxidases (DyPs), which catalyze remarkable reactions such as peroxide-driven oxygen transfer and cleavage of anthraquinone derivatives, respectively, and represent own separate peroxidase superfamilies. Furthermore, several aspects of the “classic” fungal heme-containing peroxidases, i.e., lignin, manganese, and versatile peroxidases (LiP, MnP, and VP), phenol-oxidizing peroxidases as well as chloroperoxidase (CPO), are discussed against the background of recent scientific developments.     

Acclimation of photosynthesis to nitrogen deficiency in Phaseolus vulgaris

Nitrogen deficiency diminishes consumption of photosynthates in anabolic metabolism. We studied adjustments of the photosynthetic machinery in nitrogen-deficient bean plants and found four phenomena. First, the number of chloroplasts per cell decreased. Chloroplasts of nitrogen starved leaves contained less pigments than those of control leaves, but the in vitro activities of light reactions did not change when measured on chlorophyll basis. Second, nitrogen deficiency induced cyclic electron transfer. The amounts of Rubisco and ferredoxin-NADP⁺ reductase decreased in nitrogen starved plants. Low activities of these enzymes are expected to lead to increase in reduction of oxygen by photosystem I. However, diaminobenzidine staining did not reveal hydrogen peroxide production in nitrogen starved plants. Measurements of far-red-light-induced redox changes of the primary donor of photosystem I suggested that instead of producing oxygen radicals, nitrogen starved plants develop a high activity of cyclic electron transport that competes with oxygen for electrons. Nitrogen starvation led to decrease in photochemical quenching and increase in non-photochemical quenching, indicating that cyclic electron transport reduces the plastoquinone pool and acidifies the lumen. A third effect is redistribution of excitation energy between the photosystems in favor of photosystem I. Thus, thylakoids of nitrogen starved plants appeared to be locked in state 2, which further protects photosystem II by decreasing its absorption cross-section. As a fourth response, the proportion of non-Q_B-reducing photosystem II reaction centers increased and the redox potential of the Q_B/Q_B⁻ pair decreased by 25 mV in a fraction of photosystem II centers of nitrogen starved plants.     

Transient viral replication during analytical treatment interruptions in SIV infected macaques can alter the rebound-competent viral reservoir

Analytical treatment interruptions (ATIs) of antiretroviral therapy (ART) play a central role in evaluating the efficacy of HIV-1 treatment strategies targeting virus that persists despite ART. However, it remains unclear if ATIs alter the rebound-competent viral reservoir (RCVR), the virus population that persists during ART and from which viral recrudescence originates after ART discontinuation. To assess the impact of ATIs on the RCVR, we used a barcode sequence tagged SIV to track individual viral lineages through a series of ATIs in Rhesus macaques. We demonstrate that transient replication of individual rebounding lineages during an ATI can lead to their enrichment in the RCVR, increasing their probability of reactivating again after treatment discontinuation. These data establish that the RCVR can be altered by uncontrolled replication during ATI.     

Serotonin-like immunoreactivity in the central nervous system of two ixodid tick species

Immunocytochemistry was used to describe the distribution of serotonin-like immunoreactive (5HT-IR) neurons and neuronal processes in the central nervous system (CNS), the synganglion, of two ixodid tick species; the winter tick, Dermacentor albipictus and the lone star tick, Amblyomma americanum. 5HT-IR neurons were identified in the synganglion of both tick species. D. albipictus had a significantly higher number of 5HT-IR neurons than A. americanum. The labeling pattern and number of 5HT-IR neurons were significantly different between sexes in D. albipictus, but were not significantly different between sexes in A. americanum. 5HT-IR neurons that were located in the cortex of the synganglion projected processes into the neuropils, invading neuromeres in the supraesophageal ganglion including the protocerebrum, postero-dorsal, antero-dorsal and cheliceral neuromeres. In the subesophageal ganglion, dense 5HT-IR neuronal processes were found in the olfactory lobes, pedal, and opisthosomal neuromeres. Double-labeling with neurobiotin backfilled from the first leg damaged at the Haller’s organ revealed serotoninergic neuronal processes surrounding the glomeruli in the olfactory lobes. The high number of the 5HT-IR neurons and the extensive neuronal processes present in various regions of the synganglion suggest that serotonin plays a significant role in tick physiology. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recommendation by the USDA for its use. The U.S. Government’s right to retain a non-exclusive, royalty free license in and to any copyright is acknowledged.     

T cell development in the thymus: from periodic seeding to constant output

T cell development occurs in the thymus throughout life. Recent experimental findings show that the seeding of the thymus by multi-potent stem cells from the bone marrow is periodic rather than continuous, as previously assumed. However it is well known that the output rate of cells from the thymus is relatively constant. A quantitative model is used to verify the current hypotheses regarding T cell development in the steady state mouse thymus. The results show that the thymus could be at a periodic steady state with out-of-phase thymocyte populations. Experiments to examine possible periodic fluctuations in the thymus are proposed and methods for further analysis are outlined.     

Modelling the niche for a marine vertebrate: a case study incorporating behavioural plasticity,proximate threats and climate change

The integration of satellite telemetry, remotely sensed environmental data, and habitat/environmental modelling has provided for a growing understanding of spatial and temporal ecology of species of conservation concern. The Republic of Cape Verde comprises the only substantial rookery for the loggerhead turtle Caretta caretta in the eastern Atlantic. A size related dichotomy in adult foraging patterns has previously been revealed for adult sea turtles from this population with a proportion of adults foraging neritically, whilst the majority forage oceanically. Here we describe observed habitat use and employ ecological niche modelling to identify suitable foraging habitats for animals utilising these two distinct behavioural strategies. We also investigate how these predicted habitat niches may alter under the influence of climate change induced oceanic temperature rises. We further contextualise our niche models with fisheries catch data and knowledge of fisheries ‘hotspots’ to infer threat from fisheries interaction to this population, for animals employing both strategies. Our analysis revealed repeated use of coincident oceanic habitat, over multiple seasons, by all smaller loggerhead turtles, whilst larger neritic foraging turtles occupied continental shelf waters. Modelled habitat niches were spatially distinct, and under the influence of predicted sea surface temperature rises, there was further spatial divergence of suitable habitats. Analysis of fisheries catch data highlighted that the observed and modelled habitats for oceanic and neritic loggerhead turtles could extensively interact with intensive fisheries activity within oceanic and continental shelf waters of northwest Africa. We suggest that the development and enforcement of sustainable management strategies, specifically multi‐national fisheries policy, may begin to address some of these issues; however, these must be flexible and adaptive to accommodate potential range shift for this species.     

Quantitative Changes in Gimap3 and Gimap5 Expression Modify Mitochondrial DNA Segregation in Mice

Mammalian mitochondrial DNA (mtDNA) is a high-copy maternally inherited genome essential for aerobic energy metabolism. Mutations in mtDNA can lead to heteroplasmy, the co-occurence of two different mtDNA variants in the same cell, which can segregate in a tissue-specific manner affecting the onset and severity of mitochondrial dysfunction. To investigate mechanisms regulating mtDNA segregation we use a heteroplasmic mouse model with two polymorphic neutral mtDNA haplotypes (NZB and BALB) that displays tissue-specific and age-dependent selection for mtDNA haplotypes. In the hematopoietic compartment there is selection for the BALB mtDNA haplotype, a phenotype that can be modified by allelic variants of Gimap3. Gimap3 is a tail-anchored member of the GTPase of the immunity-associated protein (Gimap) family of protein scaffolds important for leukocyte development and survival. Here we show how the expression of two murine Gimap3 alleles from Mus musculus domesticus and M. m. castaneus differentially affect mtDNA segregation. The castaneus allele has incorporated a uORF (upstream open reading frame) in-frame with the Gimap3 mRNA that impairs translation and imparts a negative effect on the steady-state protein abundance. We found that quantitative changes in the expression of Gimap3 and the paralogue Gimap5, which encodes a lysosomal protein, affect mtDNA segregation in the mouse hematopoietic tissues. We also show that Gimap3 localizes to the endoplasmic reticulum and not mitochondria as previously reported. Collectively these data show that the abundance of protein scaffolds on the endoplasmic reticulum and lysosomes are important to the segregation of the mitochondrial genome in the mouse hematopoietic compartment.     

Work ability in midlife as a predictor of mortality and disability in later life: a 28-year prospective follow-up study

Background

Poor work ability correlates with increased morbidity and early retirement from the workforce, but the association in old age is not known. We investigated work ability in midlife among white-collar and blue-collar employees as a predictor of mortality and disability 28 years later.

Methods

A total of 5971 occupationally active people aged 44–58 years participated in the Finnish Longitudinal Study of Municipal Employees (FLAME) in 1981. Perceived work ability relative to lifetime best was categorized as excellent, moderate or poor. In 2009, the ability to perform activities of daily living was assessed among 2879 respondents (71.0% of the survivors). Mortality data were available up to July 2009.

Results

At the 28-year follow-up, 1918 of the 5971 participants had died and 1403 had some form of disability. Rates of death per 1000 person-years among white-collar men were 7.7 for those with excellent work ability, 14.7 for those with moderate work ability and 23.5 for those with poor work ability. Among blue-collar men, the corresponding rates were 15.5, 20.2 and 25.3. In women, rates ranged between 6.3 and 10.6 per 1000 person-years. The age-adjusted hazard ratios (HRs) for mortality were two to three times higher among blue-collar male employees with lower work ability than among white-collar male employees with excellent work ability in midlife (i.e., the reference group). The odds of death or disability at follow-up compared with white-collar workers with excellent work ability were highest among blue-collar employees with poor work ability in midlife (odds ratio [OR] 4.56, 95% confidence interval [CI] 2.82–7.37 for men; OR 3.37, 95% CI 2.28–4.98 for women). Among the survivors, similar but slightly lower risks of disability 28 years later were found.

Interpretation

Perceived poor work ability in midlife was associated with accelerated deterioration in health and functioning and remains evident after 28 years of follow-up.Prospective studies with a follow-up time stretching from midlife to old age have shown that lower socioeconomic status, as indicated by lower education level or occupational grade, predicts a decline in health and functioning in the working population.^1–4 This association is similar, if not more pronounced, in old age.^5–7Higher levels of work-related mental and physical strain increase the risk of early retirement and predict a decline in health and an increase in mortality among the working population.^3,8–15 However, the association between the demands of the work in conjunction with inadequate mental or physical resources (i.e., work ability)¹⁶ and health and functioning in old age has not been studied.¹⁷ Using a population-based 28-year follow-up study involving middle-aged municipal employees, we investigated whether work ability in midlife predicts the risk of death and disability during old age among white-collar and blue-collar employees.