Assessment of Polygala paniculata (Polygalaceae) characteristics for evolutionary studies of legume–rhizobia symbiosis

Root nodule (RN) symbiosis is a mutualistic interaction observed between nitrogen-fixing soil bacteria and nodulating plants, which are scattered in only four orders of angiosperms called nitrogen-fixing clade. Most of legumes engage in RN symbiosis with rhizobia. Molecular genetic analyses with legumes and non-leguminous nodulating plants revealed that RN symbiosis utilizes early signalling components that are required for symbiosis with arbuscular mycorrhizal (AM) fungi. However detailed evolutionary processes are still largely unknown. Comparative analyses with non-nodulating species phylogenetically related to legumes could be better strategies to study the evolution of RN symbiosis in legumes. Polygala paniculata is a non-leguminous species that belongs to a family different from legumes but that is classified into the same order, Fabales. It has appropriate characteristics for cultivation in laboratories: small body size, high fertility and short lifecycles. Therefore, we further assessed whether this species is suitable as a model species for comparative studies with legumes. We first validated that the plant we obtained in Palau was truly P. paniculata by molecular phylogenetic analysis using rbcL sequences. The estimated genome size of this species was less than those of two model legumes, Lotus japonicus and Medicago truncatula. We determined conditions for cultivation in vitro and for hairy root formation from P. paniculata seedlings. It would facilitate to investigate gene functions in this species. The ability of P. paniculata to interact with AM fungi was confirmed by inoculation with Rhizophagus irregularis, suggesting the presence of early signalling factors that might be involved in RN symbiosis. Unexpectedly, branching of root hairs was observed when inoculated with Mesorhizobium loti broad host range strain NZP2037, indicating that P. paniculata has the biological potential to respond to rhizobia. We propose that P. paniculata is used as a model plant for the evolutionary study of RN symbiosis.

     

Symbiotic effectiveness and response to mannitol-mediated osmotic stress of various chickpea–rhizobia associations

Thirty-six symbiotic associations involving six chickpea cultivars against six rhizobial strains were evaluated for symbiotic performance and responses to osmotic stress applied by mannitol (50 mM) in aerated hydroponic cultures. Analyses in different symbioses were focused on biomass production, nodulation, nitrogen fixation, and their modulation under osmotic stress conditions, as well as expression of nodular antioxidant enzymes. Mesorhizobium ciceri reference (835) and local (CMG6) strains, as well as the local (C₁₁) M. mediterraneum allowed the best symbiotic efficiency for all chickpea cultivars. The osmotic stress induces severe decrease ranging 30–50% in aerial biomass and 50–70% for nitrogen fixation. Nevertheless, plants inoculated with M. ciceri (835) and M. mediterraneum (C₁₁) preserve a relatively high growth (4 g plant⁻¹) with nitrogen-fixing activity (25 μmols h⁻¹ plant⁻¹). The bacterial partner was the most important factor of variance of the analysed parameters in osmotic stress or physiological conditions where it gets to 60–85%. The strains allowing the best competent symbioses were proposed for field assays. Under osmotic stress, nodular peroxidase (POX) and ascorbate peroxidase (APX) activities were significantly enhanced. The increase of POX and APX was inversely correlated with the inhibition of aerial biomass production (p = 0.05) and nitrogen-fixing capacity (p = 0.01), suggesting a protective role of these enzymes in nodules. Superoxide dismutase (SOD) was also activated in stressed nodules. However, the spectacular decrease in catalase (CAT) activity discounts its involvement in osmotic stress response.     

Quantitative phosphoproteomic analyses provide evidence for extensive phosphorylation of regulatory proteins in the rhizobia–legume symbiosis

Plant Molecular Biology - PsLecRLK overexpression in rice provides tolerance against salinity stress and cause upregulation of SOS1 pathway genes, which are responsible for extrusion of excess Na+...     

Conspecific and heterospecific plant–soil biota interactions of Lonicera japonica in its native and introduced range: implications for invasion success

Plant Ecology - We tested the ‘enemy release hypothesis’ in relation to Lonicera japonica to determine the effects of soil microbes on plant growth. It was hypothesized that plant...     

Assessment of cartilage invasion in case of laryngeal cancer by means of longitudinal sectioning for histopathology – Clinical implications

AimThe aim of the study was to assess the accuracy of radiological diagnosis of laryngeal cartilage infiltration by histopathological examination of laryngeal specimen after total laryngectomy.BackgroundDespite the development of new medical technologies and significant clinical advances allowing early diagnosis and treatment of laryngeal cancer, mortality is still on the rise. Neoplastic infiltration of the laryngeal cartilages is the most common source of error in the assessment of cancer staging. Furthermore, cartilage invasion is listed as a contraindication to partial surgical techniques as well as radiotherapy.Materials and methodsThe study was carried out on 21 larynges following total laryngectomy. Before taking the decision to perform surgery, high-resolution CT scans were performed in all cases. An extended histopathological examination was conducted using a unique vertical cross-section of the whole larynx.ResultsPathology reported 2 cases of arytenoid cartilage invasion, 5 cases of cricoid cartilage invasion, 12 cases of thyroid cartilage penetration, 1 case of internal cortex invasion and 9 cases of extra-laryngeal spread. CT imaging identified 8 of 13 cases (61.5%) of pathologically proven invasion of thyroid cartilage and only 2 cases (2/9, 22%) of extra-laryngeal spread. According to CT results, arytenoid cartilage invasion was correctly identified in 2 cases, cricoid cartilage invasion in 4 (4/5, 80%). The positive predictive values for thyroid, cricoid and arytenoid cartilage invasion and penetration were 80%, 66.7% and 50%, respectively. In case of pre-laryngeal spread the positive predictive value was 100%.ConclusionDespite increasingly advanced methods involved in the diagnosis of laryngeal cancer, many discrepancies may be observed between the radiological and histopathological assessments. CT imaging has limitations especially in thyroid cartilage penetration and extra-laryngeal spread assessment in advanced laryngeal cancer cases. An extended histopathological examination, involving vertical cross-sections of the whole larynx is a very precise study that allows a precise determination of local cancer staging (T).     

Flexibility and specificity of the cohesin–dockerin interaction: implications for cellulosome assembly and functionality

Cellulosomes are highly elaborate multi-enzyme complexes of Carbohydrate Active enZYmes (CAZYmes) secreted by cellulolytic microorganisms, which very effectively degrade the most abundant polymers on Earth, cellulose and hemicelluloses. Cellulosome assembly requires that a non-catalytic dockerin module found in cellulosomal enzymes binds to one of the various cohesin domains located in a large molecular scaffold called Scaffoldin. A diversity of cohesin–dockerin binding specificities have been described, the combination of which may result in complex plant cell wall degrading systems, maximising the synergy between enzymes in order to improve catalytic efficiency. Structural studies have allowed the spatial flexibility inherent to the cellulosomal system to be determined. Recent progress achieved from the study of the fundamental cohesin and dockerin units involved in cellulosome assembly will be reviewed.     

Differential δC and δN signatures among scallop tissues: implications for ecology and physiology

There have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle) of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators [stable carbon and nitrogen isotope ratios, biochemical components and seston chlorophyll-a (chl a)] to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, δ¹⁵N appears powerful to track metabolite fates in the scallop P. maximus.     

Plantations of exotic tree species in Britain: irrelevant for biodiversity or novel habitat for native species?

Novel or emergent ecosystems arising from human action present both threats and opportunities for biodiversity. It has been suggested that exotic species can “facilitate” or “inhibit” native biodiversity through habitat modification. In Britain, there is a discussion over the contribution to biodiversity of plantations of exotic conifer species as these are commonly thought to have little relevancy as a habitat for native biodiversity. To address this we compared the species richness of a range of different taxonomic groups (lichens, bryophytes, fungi, vascular plants, invertebrates and songbirds) in exotic and native forest stands of differing structural stages in northern and southern Britain. In terms of overall native species-richness there was no significant difference between the exotic and the native stands. In the north, six species groups showed higher values in the exotic Sitka spruce (Picea sitchensis) stands with the remaining six showing higher values in the native Scots pine (Pinus sylvestris) stands. Most notably, lichen species richness was much lower in the exotic stands compared to the native stands, whereas bryophyte and fungal species richness was proportionately higher in the exotic stands. In the south, five species groups (all invertebrate taxa) showed higher species richness in exotic Norway spruce (Picea abies) stands compared to native oak (Quercus robur) stands. Five species groups had higher species-richness in the oak stands, in particular lichens and fungi. It is concluded that emergent ecosystems of exotic conifer species are not irrelevant to biodiversity. Where already well-established they can provide habitat for native species particularly if native woodland is scarce and biodiversity restoration is an immediate priority.     

Optimization of novel and greener approach for the coproduction of uricase and alkaline protease in Bacillus licheniformis by Box–Behnken model

This study explores a novel concept of coproduction of uricase and alkaline protease by Bacillus licheniformis using single substrate in single step. Seven local bacterial strains were screened for uricase production, amongst which B. licheniformis is found to produce highest uricase along with alkaline protease. Optimization of various factors influencing maximum enzyme coproduction by B. licheniformis is performed. Maximum enzyme productivity of 0.386?U/mL uricase and 0.507?U/mL alkaline protease is obtained at 8?hr of incubation period, 1% (v/v) inoculum, and at 0.2% (w/v) uric acid when the organism is cultivated at 25°C, 180?rpm, in a media containing xylose as a carbon source, urea as a nitrogen source, and initial pH of 9.5. The statistical experimental design method of Box–Behnken was further applied to obtain optimal concentration of significant parameters such as pH (9.5), uric acid concentration (0.1%), and urea concentration (0.05%). The maximum uricase and alkaline protease production by B. licheniformis using Box–Behnken design was 0.616 and 0.582?U/mL, respectively, with 1.6- and 1.13-fold increase as compared to one factor at a time optimized media. This study will be useful to develop an economic, commercially viable, and scalable process for simultaneous production of uricase and protease enzymes.     

A review of shark agonistic displays: comparison of display features and implications for shark–human interactions

Agonistic displays in 23 species of sharks of six families are described and illustrated. These displays are reviewed in terms of ethological concepts and shark hydrodynamic models. Shark agonistic displays feature many common elements rendering them readily distinguishable from normal swimming and pseudodisplays caused by sharksucker irritation. Shark agonistic displays are most readily elicited by rapid, direct diver approach when food is absent and potential escape routes restricted. Such displays appear to be motivated by defence of self or the immediately surrounding space rather than defence of territory or resources. Costs and benefits of display versus attack in shark–shark and shark–diver contests are evaluated using payoff matrices and optimal strategies are identified. Shark–human interactions are modelled in terms of a system of nested critical approach distances. For divers faced with a displaying shark, responses which may decrease the likelihood of defensive attack are suggested. Recommendations for future work on shark agonistic behaviour are offered.     

Differential effect of nitric oxide on glutathione metabolism and mitochondrial function in astrocytes and neurones: implications for neuroprotection/neurodegeneration?

Primary culture rat astrocytes exposed to the long acting nitric oxide donor (Z)-1-[2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NO) for 24 h approximately double their concentration of glutathione (GSH) and show no sign of cell death. In contrast, GSH was depleted by 48%, and significant loss of mitochondrial respiratory chain complex activity and cell death were observed in primary culture rat neurones subjected to DETA-NO for 18 h. Northern blot analysis suggested that mRNA amounts of both subunits of glutamate-cysteine ligase (GCL), the rate-limiting enzyme in GSH synthesis, were elevated in astrocytes following nitric oxide (NO) exposure. This correlated with an increase in astrocytic GCL activity. Neurones on the other hand did not exhibit increased GCL activity when exposed to NO. In addition, the rate of GSH efflux was doubled and gamma-glutamyltranspeptidase (gamma-GT) activity was increased by 42% in astrocytes treated with NO for 24 h. These results suggest that astrocytes, but not neurones, up-regulate GSH synthesis as a defence mechanism against excess NO. It is possible that the increased rate of GSH release and activity of gamma-GT in astrocytes may have important implications for neuroprotection in vivo by optimizing the supply of GSH precursors to neurones in close proximity.     

Sward characteristics and performance of dairy cows in organic grass–legume pastures shaded by tropical trees

The silvopastoral system (SPS) has been suggested to ensure sustainability in animal production systems in tropical ecosystems. The objective of this study was to evaluate pasture characteristics, herbage intake, grazing activity and milk yield of Holstein×Zebu cows managed in two grazing systems (treatments): SPS dominated by a graminaceous forage (Brachiaria decumbens) intercropped with different leguminous herbaceous forages (Stylosanthes spp., Pueraria phaseoloides and Calopogonium mucunoides) and legume trees (Acacia mangium, Gliricidia sepium and Leucaena leucocephala), and open pasture (OP) of B. decumbens intercropped only with Stylosanthes spp. Pastures were managed according to the rules for organic cattle production. The study was carried out by following a switch back format with 12 cows, 6 for each treatment, over 3 experimental years. Herbage mass was similar (P>0.05) for both treatments, supporting an average stocking rate of 1.23 AU/ha. Daily dry matter intake did not vary (P>0.05) between treatments (average of 11.3±1.02 kg/cow per day, corresponding to 2.23±0.2% BW). Milk yield was higher (P<0.05; 10.4±0.06 kg/cow per day) in the SPS than in the OP (9.5±0.06 kg/cow per day) during the 1^st year, but did not significantly differ (P>0.05) in subsequent years. The highest (P<0.05) values for herbage mass and milk yield were observed during the 3^rd year. In the SPS, with moderate shade (19% shade relative to a full-sun condition), the grass CP was higher (P<0.05) than in the OP, although the NDF content and digestibility coefficient were not modified. The animals spent more time (P<0.05) idling in the SPS than in OP. The higher legume proportion in the SPS was associated with the higher CP level in B. decumbens relative to the OP, which could explain the better (P<0.05) performance of the cows in silvopastoral areas during the 1^st year. However, during the 2^nd and 3^rd years, similarities in the legume percentages of both systems resulted in similar (P>0.05) milk yields. Low persistence of Stylosanthes guianensis was observed over the experimental period, indicating that the persistence of forage legumes under grazing could be improved using adapted cultivars that have higher annual seed production. The SPS and a diversified botanical composition of the pasture using legume species mixed with grasses are recommended for organic milk production.     

Proteolytic cleavage of extracellular α-synuclein by plasmin: implications for Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disease characterized by a progressive dopaminergic neuronal loss in association with Lewy body inclusions. Gathering evidence indicates that α-synuclein (α-syn), a major component of the Lewy body, plays an important role in the pathogenesis of PD. Although α-syn is considered to be a cytoplasmic protein, it has been detected in extracellular biological fluids, including human cerebrospinal fluid and blood plasma of healthy and diseased individuals. In addition, a prion-like spread of α-syn aggregates has been recently proposed to contribute to the propagation of Lewy bodies throughout the nervous system during progression of PD, suggesting that the metabolism of extracellular α-syn might play a key role in the pathogenesis of PD. In the present study, we found that plasmin cleaved and degraded extracellular α-syn specifically in a dose- and time- dependent manner. Aggregated forms of α-syn as well as monomeric α-syn were also cleaved by plasmin. Plasmin cleaved mainly the N-terminal region of α-syn and also inhibited the translocation of extracellular α-syn into the neighboring cells in addition to the activation of microglia and astrocytes by extracellular α-syn. Further, extracellular α-syn regulated the plasmin system through up-regulation of plasminogen activator inhibitor-1 (PAI-1) expression. These findings help to understand the molecular mechanism of PD and develop new therapeutic targets for PD.     

Habitat complexity modifies ant–parasitoid interactions: implications for community dynamics and the role of disturbance

Species must balance effective competition with avoidance of mortality imposed by predators or parasites to coexist within a local ecological community. Attributes of the habitat in which species interact, such as structural complexity, have the potential to affect how species balance competition and mortality by providing refuge from predators or parasites. Disturbance events such as fire can drastically alter habitat complexity and may be important modifiers of species interactions in communities. This study investigates whether the presence of habitat complexity in the form of leaf litter can alter interactions between the behaviorally dominant host ants Pheidole diversipilosa and Pheidole bicarinata, their respective specialist dipteran parasitoids (Phoridae: Apocephalus sp. 8 and Apocephalus sp. 25) and a single species of ant competitor (Dorymyrmex insanus). We used a factorial design to manipulate competition (presence/absence of competitors), mortality risk (presence/absence of parasitoids) and habitat complexity (presence/absence of leaf litter). Parasitoid presence reduced soldier caste foraging, but refuge from habitat complexity allowed increased soldier foraging in comparison to treatments in which no refuge was available. Variation in soldier foraging behavior correlated strongly with foraging success, a proxy for colony fitness. Habitat complexity allowed both host species to balance competitive success with mortality avoidance. The effect of fire on habitat complexity was also studied, and demonstrated that the immediate negative impact of fire on habitat complexity can persist for multiple years. Our findings indicate that habitat complexity can increase dominant host competitive success even in the presence of parasitoids, which may have consequences for coexistence of subordinate competitors and community diversity in general.     

Biodiversity and biogeography of middle–late liassic ammonoids: implications for the early Toarcian mass extinction

In Western Tethyan areas, the Toarcian stage begins with two important evolutionary events in ammonite faunas: (1) the disruption of Tethyan–Boreal provinciality; (2) a biological crisis linked with the oceanic anoxic event OAE. The analysis of these events has been addressed by constructing curves of ammonoid diversity (species richness, origination and extinction rates) in the Late Pliensbachian (= Domerian)–Early Toarcian interval in selected localities. Two diversity drops are recognized. The first one is recorded at the end of the Dactylioceras mirabile subzone and reflects the disruption of Tethyan–Boreal provinciality, through the progressive extinction of the Boreal endemic family Amaltheidae that occupied the north-western European seas during the whole Pliensbachian on the one hand, and the extinction of Late Domerian Ammonitina endemic to the Mediterranean areas on the other hand. The Early Toarcian homogeneization of Mediterranean and north-western European ammonoid faunas was reached via elimination of both Boreal and Mediterranean endemics with differential rates of extinction in the two palaeogeographic domains and the subsequent geographical expansion of Tethyan-derived ammonoids. The second, dramatic drop in ammonite diversity in the upper part of the Dactylioceras semicelatum subzone coincided with the onset of OAE. It also affected epioceanic ammonoid clades like Phyllocerataceae and Lytocerataceae. These two drops are interpreted as two distinct extinctions and not as episodes of a single, stepwise event. Complex relations between ammonoid diversity and sea-level changes are suggested by trends in endemism, which may be reversed during either a single transgression or a single regression.     

The ecological role of moss in a polar desert: implications for aboveground–belowground and terrestrial–aquatic linkages

The McMurdo Dry Valleys of Antarctica is one of the coldest and driest habitats on the planet. As vascular plants are absent in this region, moss is the main form of aboveground primary production with a potentially important contribution to biogeochemical cycling, yet little is known about their ecological role. To determine the relationship between moss and soil properties relevant to biogeochemistry, we sampled both from a variety of locations in the Dry Valleys. Moss presence was compared to soil properties, and we measured the plasticity of moss stoichiometry (C:N:P) across gradients in nutrient availability. Results demonstrate that many soil properties significantly differed with moss presence, particularly conductivity and pH, but there is no strong evidence that this is caused by the moss presence and not the conditions inherent to the microsites where moss was found. There is great variability in moss stoichiometry, with some significant differences between sites, but generally variability within sites is larger than variation among sites. Results suggest that the main source of moss nutrients is from the soil, rather than water, but correlations with any one nutrient source are weak, suggesting a great deal of plasticity in moss stoichiometry and nutrient uptake.