Modelling hydrolysis of leaf litter by digestive enzymes of the snail Melanopsis praemorsa: combination of response surface methodology and in vitro assays

The objective of the present study was to test the application of an in vitro assay simulating the digestive hydrolysis of leaf litter by the freshwater snail M. praemorsa, as well as to determine the possible influence of different factors in the efficiency of such process to release biologically available C and N under the forms of reducing sugars and amino acids from two different substrates. A novel approach to construct a model explaining the effect of three main factors (temperature, total reaction time and enzyme:substrate ratio) in the digestive hydrolysis of cellulose and protein present in leaf litter of different nutritive value is used. The methodology combines a factorial design based in the response surface methodology (RSM) and in vitro digestibility assays adapted to the physiology of both plant substrates used (alder and poplar leaves). The model revealed a different influence of the factors in the hydrolysis of two plant substrates, poplar and alder leaves and the main effect was produced by the time available for hydrolysis. A compensation response based in a longer gut retention time for the lower quality substrate was observed in the feeding assays. The use of in vitro assays and RSM provides a useful insight on the effect of factors and mechanisms underlying the observed differences in nutritional value of leaf litter for an aquatic invertebrate, being such differences linked to the whole bioavailability of carbon and nitrogen in headwater streams.     

Dietary regulation of hypodermal polyploidization in <Emphasis Type="Italic">C. elegans</Emphasis>

Background  

Dietary restriction (DR) results in increased longevity, reduced fecundity and reduced growth in many organisms. Though many studies have examined the effects of DR on longevity and fecundity, few have investigated the effects on growth.     

miR-58 family and TGF-β pathways regulate each other in Caenorhabditis elegans

Despite the fact that microRNAs (miRNAs) modulate the expression of around 60% of protein-coding genes, it is often hard to elucidate their precise role and target genes. Studying miRNA families as opposed to single miRNAs alone increases our chances of observing not only mutant phenotypes but also changes in the expression of target genes. Here we ask whether the TGF-β signalling pathways, which control many animal processes, might be modulated by miRNAs in Caenorhabditis elegans. Using a mutant for four members of the mir-58 family, we show that both TGF-β Sma/Mab (controlling body size) and TGF-β Dauer (regulating dauer, a stress-resistant larval stage) are upregulated. Thus, mir-58 family directly inhibits the expression of dbl-1 (ligand), daf-1, daf-4 and sma-6 (receptors) of TGF-β pathways. Epistasis experiments reveal that whereas the small body phenotype of the mir-58 family mutant must invoke unknown targets independent from TGF-β Sma/Mab, its dauer defectiveness can be rescued by DAF-1 depletion. Additionally, we found a negative feedback loop between TGF-β Sma/Mab and mir-58 and the related mir-80. Our results suggest that the interaction between mir-58 family and TGF-β genes is key on decisions about animal growth and stress resistance in C. elegans and perhaps other organisms.     

Structural studies on some saponins from Lecaniodiscus cupanioides

Four triterpenoid saponins isolated from the stem bark of Lecaniodiscus cupanioides and denoted S-2,S-3,S-4 and S-5, were identified as follows. S-2:3-O-[α-l-arabinopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl]-hederagenin; S-3:3-O-[α-d-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabino-pyranosyl ]-hederagenin; S-4:3-O- [α-l-arabinopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→ 2)-α-l-arabinopyranosyl]-hederagenin; S-5:3-O- [α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl ]-hederagenin. Of these, S-2 and S-4 are new substances.     

The RNA-binding protein Gemin5 binds directly to the ribosome and regulates global translation

RNA-binding proteins (RBPs) play crucial roles in all organisms. The protein Gemin5 harbors two functional domains. The N-terminal domain binds to snRNAs targeting them for snRNPs assembly, while the C-terminal domain binds to IRES elements through a non-canonical RNA-binding site. Here we report a comprehensive view of the Gemin5 interactome; most partners copurified with the N-terminal domain via RNA bridges. Notably, Gemin5 sediments with the subcellular ribosome fraction, and His-Gemin5 binds to ribosome particles via its N-terminal domain. The interaction with the ribosome was lost in F381A and Y474A Gemin5 mutants, but not in W14A and Y15A. Moreover, the ribosomal proteins L3 and L4 bind directly with Gemin5, and conversely, Gemin5 mutants impairing the binding to the ribosome are defective in the interaction with L3 and L4. The overall polysome profile was affected by Gemin5 depletion or overexpression, concomitant to an increase or a decrease, respectively, of global protein synthesis. Gemin5, and G5-Nter as well, were detected on the polysome fractions. These results reveal the ribosome-binding capacity of the N-ter moiety, enabling Gemin5 to control global protein synthesis. Our study uncovers a crosstalk between this protein and the ribosome, and provides support for the view that Gemin5 may control translation elongation.     

Effects of azaperone and haloperidol on the stress response of drive-net captured Iberian ibexes (<Emphasis Type="Italic">Capra pyrenaica</Emphasis>)

The physical capture of wild ungulates is performed for different purposes when anesthesia in field conditions is not possible or advisable. The use of tranquilizers may contribute to improved welfare of captured animals. This study aimed to evaluate the effect of azaperone and haloperidol on the stress response of Iberian ibex (Capra pyrenaica) through the evaluation of physiological, hematological, and serum biochemical parameters. Thirty-five Iberian ibexes were drive-net captured and randomly injected with azaperone (0.52 ± 0.07 mg/kg intramuscularly (IM); n = 10), haloperidol (0.17 ± 0.04 mg/kg IM; n = 10), or saline (0.5 mL IM; n = 15) and physically restrained for 3 h. The variability of heart rate was lower in the azaperone-treated ibexes, suggesting a calming effect, and erythrocyte and biochemical parameters indicated vasodilation, splenic sequestration, hemodilution, improvement of renal perfusion, and a protective effect on muscle as a result of smooth muscle relaxation induced by azaperone. Haloperidol showed poorer results, maybe due to insufficient dosage. These results support the suitability of using azaperone in capture operations of Iberian ibex in order to reduce stress and prevent its adverse effects.     

Evolutionary history of Na,K-ATPases and their osmoregulatory role

The Na/K pump, or Na,K-ATPase, is a key enzyme to the homeostasis of osmotic pressure, cell volume, and the maintenance of electrochemical gradients. Its α subunit, which holds most of its functions, belongs to a large family of ATPases known as P-type, and to the subfamily IIC, which also includes H,K-ATPases. In this study, we attempt to describe the evolutionary history of IIC ATPases by doing phylogenetic analysis with most of the currently available protein sequences (over 200), and pay special attention to the relationship between their diversity and their osmoregulatory role. We include proteins derived from many completed or ongoing genome projects, many of whose IIC ATPases have not been phylogenetically analyzed previously. We show that the most likely origin of IIC proteins is prokaryotic, and that many of them are present in non-metazoans, such as algae, protozoans or fungi. We also suggest that the pre-metazoan ancestor, represented by the choanoflagellate Monosiga brevicollis, whose genome has been sequenced, presented at least two IIC-type proteins. One of these proteins would have given rise to most current animal IIC ATPases, whereas the other apparently evolved into a lineage that, so far, has only been found in nematodes. We also propose that early deuterostomes presented a single IIC gene, from which all the extant diversity of vertebrate IIC proteins originated by gene and genome duplications. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic diversity,genetic structure and phylogeography of the Iberian endemic Gypsophila struthium (Caryophyllaceae) as revealed by AFLP and plastid DNA sequences: connecting habitat fragmentation and diversification

Iberian gypsum outcrops are highly fragmented and ecologically challenging environments for plant colonization. As gypsophytes occur exclusively in such habitats, they are ideal models for the study of both the effects of habitat fragmentation and selection on population genetic diversity and structure. In this study, we used amplified fragment length polymorphism (AFLP) and plastid DNA sequences to investigate the phylogeographical history of the Iberian plant Gypsophila struthium (Caryophyllaceae), a widespread endemic restricted to Iberian gypsum outcrops. Gypsophila struthium consists of two subspecies that differ in the architecture of their inflorescence and have mostly allopatric ranges. Gypsophila struthium subsp. struthium occurs in central, eastern and south‐eastern Iberia, whereas G. struthium subsp. hispanica occurs in northern and eastern areas. AFLPs revealed low but significant genetic differentiation between the subspecies, probably as a result of a recent diversification during the Pliocene–Pleistocene. In the geographical contact zone between the taxa, the Bayesian analyses revealed populations with mixed ancestries and genetic clusters predominantly of one or the other subspecies, indicating incomplete reproductive barriers between them. Plastid DNA haplotypes revealed strong geographical structure and testified to processes of isolation by distance and continuous range expansion for some haplotype clades. The Bayesian analyses of the population structure of AFLP data and nested clade phylogeographical analysis (NCPA) of plastid haplotypes revealed that the putative ancestral range corresponded to central and eastern populations of G. struthium subsp. struthium, with those lineages contributing through more recent expansion to increased genetic diversity and structure of the south‐eastern and eastern ranges of this subspecies and to the diversification of G. struthium subsp. hispanica in northern and eastern gypsum outcrops. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 654–675.