Water deficit tolerance in sugarcane is dependent on the accumulation of sugar in the leaf

Sugarcane productivity is severely affected by the occurrence of water deficit in the field, causing inhibition of growth and sugar production. Evaluating physiological responses of sugarcane under water deficit conditions is essential to understand physiological variables responsible for reaching homeostasis. Therefore, we analysed physiological traits of two sugarcane genotypes, RB835486 (Tolerant) and RB855453 (Susceptible), under water deficit conditions: well-watered (WW-Control), water deficit (WD) and rewatered (RW). The physiological response was evaluated using linear regression and multivariate analysis. Some characteristics such as water potential in leaves, photosynthesis, chlorophyll fluorescence, chlorophyll index, sucrose and starch contents did not show differences between the genotypes under water deficit conditions. However, the tolerant genotype showed increased reducing sugars content in the leaves, whereas the susceptible genotype had increased non-photochemical quenching (qN). After rewatering, the susceptible sugarcane genotype showed higher electron transport rate (ETR) and efficiency of PSII (Y). Multivariate analysis revealed that non-photochemical quenching and reducing sugars in the leaves were physiological variables responsible for reaching homestasis under water deficit conditions. Therefore, the reducing sugars concentration should be considered a physiological variable responsible for the adjustment made by the tolerant sugarcane genotype when submitted to water deficit.     

Male-male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs*

Terrestrial breeding is a derived condition in frogs, with multiple transitions from an aquatic ancestor. Shifts in reproductive mode often involve changes in habitat use, and these are typically associated with diversification in body plans, with repeated transitions imposing similar selective pressures. We examine the diversification of reproductive modes, male and female body sizes, and sexual size dimorphism (SSD) in the Neotropical frog genera Cycloramphus and Zachaenus, both endemic to the Atlantic rainforest of Brazil. Species in this clade either breed in rocky streams (saxicolous) or in terrestrial environments, allowing us to investigate reproductive habitat shifts. We constructed a multilocus molecular phylogeny and inferred evolutionary histories of reproductive habitats, body sizes, and SSD. The common ancestor was small, saxicolous, and had low SSD. Terrestrial breeding evolved independently three times and we found a significant association between reproductive habitat and SSD, with shifts to terrestrial breeding evolving in correlation with decreases in male body size, but not female body size. Terrestrial breeding increases the availability of breeding sites and results in concealment of amplexus, egg-laying, and parental care, therefore reducing male-male competition at all stages of reproduction. We conclude that correlated evolution of terrestrial reproduction and small males is due to release from intense male-male competition that is typical of exposed saxicolous breeding.     

Relationship between epipelon,epiphyton and phytoplankton in two limnological phases in a shallow tropical reservoir with high Nymphaea coverage

Macrophytes and phytoplankton are recognized as having roles in determining alternative stable states in shallow lakes and reservoirs, while the role of periphyton has been poorly investigated. Temporal and spatial variation of phytoplankton, epipelon and epiphyton was examined in a shallow reservoir with high abundance of aquatic macrophytes. The relationships between algae communities and abiotic factors, macrophyte coverage and zooplankton density were also analyzed. Monthly sampling was performed in three zones of the depth gradient of the reservoir. Two phases of algal dominance were found: a phytoplankton phase and epipelon phase. The phase of phytoplankton dominance was characterized by high macrophyte coverage. Rotifera was the dominant zooplankton group in all the zones. Flagellate algae were dominant in phytoplankton, epipelon and epiphyton. Macrophyte coverage was found to be a predictor for algal biomass. Changes in biomass and species composition were associated with macrophyte cover variation, mainly the Nymphaea. In addition to the abiotic factors, the macrophyte coverage was a determining factor for changes to the algal community, contributing to the alternation between dominance phases of phytoplankton and epipelon. The macrophyte–phytoplankton–periphyton relationship needs to be further known in shallow reservoirs, especially the role of epipelon as an alternate stable state.

     

Loss of phytoplankton functional and taxonomic diversity induced by river regulation in a large tropical river

Hydrobiologia - Human activities have disrupted the functioning of river ecosystems around the world. In the Amazon basin, hydropower expansion has affected diversity patterns, but no study has...     

Memory in Ion Channel Kinetics

Acta Biotheoretica - Ion channels are transport proteins present in the lipid bilayers of biological membranes. They are involved in many physiological processes, such as the generation of nerve...     

Death receptors and mitochondria: Two prime triggers of neural apoptosis and differentiation

Background

Stem cell therapy is a strategy far from being satisfactory and applied in the clinic. Poor survival and differentiation levels of stem cells after transplantation or neural injury have been major problems. Recently, it has been recognized that cell death-relevant proteins, notably those that operate in the core of the executioner apoptosis machinery are functionally involved in differentiation of a wide range of cell types, including neural cells.

Scope of review

This article will review recent studies on the mechanisms underlying the non-apoptotic function of mitochondrial and death receptor signaling pathways during neural differentiation. In addition, we will discuss how these major apoptosis-regulatory pathways control the decision between differentiation, self-renewal and cell death in neural stem cells and how levels of activity are restrained to prevent cell loss as final outcome.

Major conclusions

Emerging evidence suggests that, much like p53, caspases and Bcl-2 family members, the two prime triggers of cell death pathways, death receptors and mitochondria, may influence proliferation and differentiation potential of stem cells, neuronal plasticity, and astrocytic versus neuronal stem cell fate decision.

General significance

A better understanding of the molecular mechanisms underlying key checkpoints responsible for neural differentiation as an alternative to cell death will surely contribute to improve neuro-replacement strategies.     

Candidemia by Species of the Candida parapsilosis Complex in Children’s Hospital: Prevalence, Biofilm Production and Antifungal Susceptibility

Opportunistic infections are an increasingly common problem in hospitals, and the yeast Candida parapsilosis has emerged as an important nosocomial pathogen. The aims of this study were to determine and compare (i) the prevalence rate among C. parapsilosis complex organisms isolated from blood in a public children’s hospital in São Paulo state, (ii) the ability of the complex C. parapsilosis species identified to produce biofilm and (iii) the antifungal susceptibility profiles. Forty-nine (49) specimens of isolated blood yeast were analyzed, previously identified as C. parapsilosis by conventional methods. After the molecular analysis, the isolates were characterized as C. parapsilosis sensu stricto (83.7 %), C. orthopsilosis (10.2 %) and C. metapsilosis (6.1 %). All species were able to form biofilm. The species with the highest biofilm production was C. parapsilosis sensu stricto, followed by C. orthopsilosis and further by C. metapsilosis. All of the strains have demonstrated similar susceptibility to fluconazole, caspofungin, voriconazole, cetoconazole and 5-flucytosine. Only one strain of C. parapsilosis was resistant to amphotericin B. Regarding itraconazole, 66.6 and 43.9 % isolates of C. metapsilosis and C. parapsilosis, respectively, have demonstrated to be susceptible dose-dependent, with one isolate of the latter species resistant to the drug. Candida parapsilosis sensu stricto has demonstrated to be the less susceptible, mainly to amphotericin B, caspofungin and “azoles” such as fluconazole. Therefore, C. metapsilosis and C. orthopsilosis are still involved in a restricted number of infections, but these data have become essential for there are very few studies of these species in Latin America.     

1914G variant of BCHE gene associated with enzyme activity,obesity and triglyceride levels

Polymorphisms of butyrylcholinesterase (BChE) have been reported to be associated to weight, BMI variance and hypertriglyceridemia in adults and adolescents. The aim of the present study was to investigate the association of −116A (SNP: G/A; rs1126680) and 1914G (SNP: A/G; rs3495) variants of BCHE gene with anthropometric and biochemical variables associated with obesity in population sample of 115 individuals, from Southern Brazil. Participants were grouped in two categories: obese (BMI ≥ 30) and non-obese (BMI < 30). The 1914G allele showed significantly higher frequency in the obese group, and carriers of 1914G allele showed lower mean BChE activity when compared to 1914A carriers (p = 0.006). Higher means of BMI (p = 0.02) and triglyceride (TG; p = 0.01) were found in 1914G carriers (BMI = 27.57kg/m²; TG = 150.8 mg/dL) when compared to 1914A homozygotes (BMI = 25.55 kg/m²; TG = 107.9 mg/dL). Carriers of the −116A allele showed lower mean BChE activity than usual homozygotes, and the −116A variant was found in cis with 1914G (p < 0.0001; D′ = 1). The region of BCHE gene that contains the 1914G mutation site is target of microRNAs (miRs) and the response of BChE to glucocorticoids is especially influenced by these miRs. Therefore, it is possible that the 1914G allele can be interfering in gluconeogenesis, hyperglycemia, lipolysis and body fat distribution. This lower activity may cause an imbalance in lipid metabolism, which may lead to an increased predisposition to obesity and to a lower ability to maintain metabolic homeostasis.     

Synthetic Condensed 1,4-naphthoquinone Derivative Shifts Neural Stem Cell Differentiation by Regulating Redox State

Naphthoquinones are bioactive compounds widespread in nature that impact on several cellular pathways, including cell proliferation and survival, by acting as prooxidants and electrophiles. We have previously described the role of the synthetic isoxazole condensed 1,4-naphthoquinone derivative 1a in preventing apoptosis induced by distinct stimuli in several cell models. In addition, apoptosis regulators and executioners may control neural stem cell (NSC) fate, without involving cell death per se. Here, we hypothesize that 1a might also play a role in NSC fate decision. We found that exposure to 1a shifts NSC differentiation potential from neurogenic to gliogenic lineage and involves the generation of reactive oxygen species, without increasing cell death. Modulation of caspases and calpains, using cysteine protease inhibitors, failed to mimic 1a effects. In addition, incubation with the naphthoquinone derivative resulted in upregulation and nuclear translocation of antioxidant responsive proteins, Nrf2 and Sirt1, which in turn may mediate 1a-directed shift in NSC differentiation. In fact, antioxidants halted the shift in NSC differentiation potential from neurogenic to gliogenic lineage, while strongly reducing reactive oxygen species generation and Nrf2 and Sirt1 nuclear translocation in NSC exposed to 1a. Collectively, these data support a new role for a specific naphthoquinone derivative in NSC fate decision and underline the importance of redox environment control.