Biochemical aspects of the developing and ripening banana

The peel and pulp of the banana fruit and the pseudostem were examined for glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT) and aldolase activities and protein, phenolics, chlorophyll and starch. The peel-pulp ratio at various stages of fruit development on the plant and in detached fruits showing incipient ripening were used as an index of the physiological age of the fruit. The enzymes exhibited maximum activity at a stage corresponding to the initiation of the climacteric. GPT level at this stage was higher than that of GOT. An initial increase in the protein content was followed by a decline in both peel and pulp, the level reaching a minimum in climacteric fruits. Astringency, measured in terms of total phenolics, decreased with development; in mature fruits, peel contained 4–5 × as much phenolics as pulp. Chlorophyll in mature fruits was 10 × higher than in young fruits and decreased in ripe fruits. The onset of ripening was attended with a pronounced decrease in the starch. The various analyses were carried out also on the pseudostem removed from the plant soon after flower formation.     

The pancreatic -cell recognition of insulin secretagogues. VII. Binding and permeation of chloromercuribenzene-p-sulphonic acid in the plasma membrane of pancreatic -cells

The uptake of chloromercuribenzene-p-sulphonic acid (CMBS) was studied in microdissected pancreatic islets of ob/ob-mice. After rapid initial binding, the uptake increased linearly with time, suggesting that CMBS diffused into the plasma membrane. The binding of CMBS was rapidly reversed on exposure to l-cysteine. Whereas glibenclamide had no effect, glucose and 4-acetamido-4′-isothiocyanostilbene-2,2′-disulphonic acid (SITS) inhibited diffusion without affecting the initial binding. SITS, but not glucose, also inhibited CMBS-induced insulin release. The results support the hypothesis that CMBS stimulates insulin release by reacting with thiol groups in the β-cell plasma membrane. These thiol groups may be located in an anion diffusion channel, entrance to which is blocked by SITS and exit from which is inhibited by glucose. In comparison with erythrocytes, the β-cells contain a large number of superficial thiol groups, which may explain why these cells accumulate alloxan.     

ULTRASTRUCTURAL BASIS OF BIOCHEMICAL EFFECTS IN A SERIES OF LETHAL ALLELES IN THE MOUSE : Neonatal and Developmental Studies

The fine structure of newborn and fetal mouse liver and of newborn kidney cells homozygous for any of three albino alleles known to have multiple biochemical effects was investigated. Electron microscope studies of mutant cells revealed dilation and vesiculation of the rough endoplasmic reticulum in parenchymal liver cells, as well as dilation and other anomalies of the Golgi apparatus. These abnormalities were observed in all newborn mutants but never in littermate controls. Although they were most pronounced in liver parenchymal cells, they were found also to a lesser degree in kidney cells, but they were absent altogether in other cell types of the mutant newborn. Homozygous fetuses showed similar anomalies in the liver at 19 days of gestational age. In one of the alleles studied, mutant liver parenchymal cells were found to be abnormal as early as the 18th day of gestation. There appears to be a striking parallelism between the biochemical defects and those of the cellular membranes in homozygous mutant newborn and fetuses. Although the specific nature of the mutational effect on membrane structure remains unknown, the results are compatible with the assumption that a mutationally caused defect in a membrane component interferes with a mechanism vital in the integration of morphological and biochemical differentiation.     

Abscisic acid biosynthesis under water stress: anomalous behavior of the 9-<Emphasis Type="Italic">cis</Emphasis>-epoxycarotenoid dioxygenase1 (<Emphasis Type="Italic">NCED1</Emphasis>) gene in rice

The gene NCED1 encodes 9-cis-epoxycarotenoid dioxygenase, which catalyzes oxidative cleavage of 9-cis-epoxycarotenoids neoxanthin and violaxanthin to xanthoxin, a key step in the biosynthesis of abscisic acid (ABA) in higher plants. In the present study, the complete NCED1 of 1 917 bp was cloned and characterized from rice (Oryza sativa L. cv. N22) as no earlier reports were available for its characterization from the indica cultivar. The NCED1 had no intron and encoded a protein of 639 amino acids with a predicted molecular mass of 68.62 kD and pI of 6.07. The aliphatic index and grand average of hydropathicity were found to be 77.04 and -0.148, respectively. Multiple alignment analysis revealed that the sequence shared a high identity with the Oryza sativa japonica group (100 %) followed by Triticum aestivum (90 %), Hordeum vulgare (90 %), and Zea mays (89 %). The enzyme had a RPE65 domain of 476 amino acid residues. The RPE65 domain requires Fe(II) as a cofactor coordinated with 4 histidine residues and 3 glutamic acid residues. The phylogenic tree shows that NCED1 of japonica rice and NCED1 of indica rice were in the same group. They might have been evolved from a common ancestor. Analysis with a PSORT III tool shows that NCED is a chloroplastic protein. The real-time quantitative PCR and RNA-sequencing studies show that the expression of NCED1 was progressively reduced with increasing water stress, and a negative correlation between expression of OsNCED1 and severity of stress was established. Further, NCED1 expression negatively correlated with ABA accumulation under water stress whereas in some other species, its expression increased along with ABA accumulation. This might be due to feedback inhibition of the ABA biosynthesis in rice.     

Large and deep perialpine lakes: a paleolimnological perspective for the advance of ecosystem science

The present paper aims at reviewing general knowledge of large European perialpine lakes as provided by sediment studies, and at outlining the contribution, from several lines of evidence, of modern paleolimnology in both interpreting past lake ecological evolution and forecasting lake responses to future human impacts. A literature survey mainly based on papers published in international journals indexed on ISI-Wos and Scopus from 1975 to April 2017 has been conducted on the 20 perialpine lakes with z_max?≥?100 m and lake area?≥?10 km², and on 4 shallower perialpine lakes representing hotspots of extensive neo- and paleo-limnological research. By pinpointing temporal and spatial differences in paleolimnological studies conducted in the Alpine countries, the review identifies knowledge gaps in the perialpine area, and shows how sediment-based reconstructions represent a powerful tool, in mutual support with limnological surveys, to help predicting future scenarios through the “past-forward” principle, which consists in reconstructing past lake responses to conditions comparable to those to come. The most recent methodological developments of sediment studies show the potential to cope with the increasing ecosystem variability induced by climate change, and to produce innovative and crucial information for tuning future management and sustainable use of Alpine waters.     

Variability in the response of amphipods and macroinvertebrate assemblage structure to prolonged drought in forested upland streams

With climate change set to increase the frequency and severity of drought in many parts of the world, there is a need to better understand the effects of drying on stream ecosystems. We investigated the long-term effects of drought on two amphipod taxa Paramoera fontana (Pontogeneiidae) and Austrogammarus australis (Paramelitidae) and macroinvertebrate assemblage structure through an analysis of 13 years of data collected from four forested stream reaches (Victoria, Australia). Abundances of A. australis and P. fontana in the lower reach of Lyrebird Creek declined to zero following surficial streambed drying. Similar declines in abundances were not observed in Sassafras Creek or the two headwater springs, which continued to flow throughout the drought. P. fontana was detected again in the lower reach of Lyrebird Creek 12 months after the final cease-to-flow, however A. australis remained undetected 5 years later, despite an upstream source population within 2 km. Both the entire and shredder macroinvertebrate assemblage structure in Sassafras Creek and the lower reach of Lyrebird Creek shifted significantly pre- and post-surficial streambed drying in the lower reach of Lyrebird Creek. Despite signs of recovery following a return to more average flows, assemblage composition remained considerably different. The substantial differences in the recovery of the two species indicates varying resistance and resilience traits. The failure of A. australis to recolonize after 5 years indicates an absence of any significant resistance or resilience traits. In contrast, the rapid re-colonization of P. fontana may indicate poor resistance traits, but strong resilience traits. The sensitivity of A. australis to cease-to-flow events points to the need to carefully manage water extraction to protect this threatened species. The effective management of macroinvertebrate assemblages in the face of drought requires a clear understanding of their response to drying, the conservation of refugia and the minimization of additional stressors which reduce ecosystem resilience.     

Interdomain salt‐bridges in the Ebola virus protein VP40 and their role in domain association and plasma membrane localization

The Ebola virus protein VP40 is a transformer protein that possesses an extraordinary ability to accomplish multiple functions by transforming into various oligomeric conformations. The disengagement of the C‐terminal domain (CTD) from the N‐terminal domain (NTD) is a crucial step in the conformational transformations of VP40 from the dimeric form to the hexameric form or octameric ring structure. Here, we use various molecular dynamics (MD) simulations to investigate the dynamics of the VP40 protein and the roles of interdomain interactions that are important for the domain–domain association and dissociation, and report on experimental results of the behavior of mutant variants of VP40. The MD studies find that various salt‐bridge interactions modulate the VP40 domain dynamics by providing conformational specificity through interdomain interactions. The MD simulations reveal a novel salt‐bridge between D45‐K326 when the CTD participates in a latch‐like interaction with the NTD. The D45‐K326 salt‐bridge interaction is proposed to help domain–domain association, whereas the E76‐K291 interaction is important for stabilizing the closed‐form structure. The effects of the removal of important VP40 salt‐bridges on plasma membrane (PM) localization, VP40 oligomerization, and virus like particle (VLP) budding assays were investigated experimentally by live cell imaging using an EGFP‐tagged VP40 system. It is found that the mutations K291E and D45K show enhanced PM localization but D45K significantly reduced VLP formation.