Morphology of the jaw apparatus in 8 species of Patellogastropoda (Mollusca, Gastropoda) with special reference to Testudinalia tesulata (Lottiidae)

The fine structure of the jaw apparatus was studied by scanning electron microscopy in eight species of Patellogastropoda. The jaw apparatus is an unpaired two-layered dorsolateral structure with anterior and posterior wings attached to the odontophore by muscles. The jaw of Testudinalia tesulata (O.F. Müller, 1776) is a derivative of the cuticle typical for the foregut. The tissue forming the jaw is a specialized foregut epithelium (gnathoepithelium), consisting of a special type of cells called gnathoblasts. The jaw grows in areas of the epithelium characterized by high concentration of electron-dense vesicles, ER and long microvilli that penetrate deep into the jaw plate. This indicates that the gnathoblasts take an active part in jaw growth. In most cases, these areas of the gnathoepithelium are highly folded. The main differences between the species studied are form and thickness of the frontal edge of the jaw. These differences do not correlate with the systematic position of the species studied but likely depend more on the feeding mode. The transmission electron microscopy studies yielded new morphological criteria for comparison between various gastropod species and other members of Trochozoa, in particular, Annelida. The jaws of Annelida are cuticular structures formed on the surface of specialized epithelial cells, often also called gnathoblasts. The jaw of Patellogastropoda can be attributed to the first type of annelid jaw formation characterized by an epithelium with long microvilli and continuous growth.     

The effect of immersion cleansers on gloss,colour and sorption of acetal denture base material

doi: 10.1111/j.1741‐2358.2012.00657.x The effect of immersion cleansers on gloss, colour and sorption of acetal denture base material Objective: To study the effect of peroxide and hypochlorite cleansers on gloss, colour and sorption of acetal denture resins. Materials and methods: Pink acetal and thermoplastic acrylic resins were evaluated. Thirty‐five specimens 39 × 39 × 1.8 mm of each resin were prepared. Each group of specimens (n = 7) was then immersed into cleansers for 100 days. Group I immersed in tap water, Group II in Corega Extradent for 5 min, Group III in Corega Extradent for 8 h, Group IV in NitrAdine? Seniors for 15 min and Group V in NaOCl 5.25%. Gloss, colour and weight measurements were taken initially and after 100 days. Data subjected to two‐way anova and Tukey’s test at α = 0.05. Results: Acrylic resin showed reductions of glossiness from ?5 to ?15 and acetal from ?0.2 to ?6. Colour changes (ΔΕ*) ranged from 2.64 to 7.64 for acrylic and 2.77 to 26.54 for acetal resin. Sorption for acrylic ranged from 11.64 to 17.06 μg/mm³ and 9.18 to 24.79 μg/mm³ for acetal resin. The results of (ΔΕ*) and sorption showed an interaction between denture resins and cleansers. Conclusions: The gloss of acetal resin was less affected by water, peroxides and NaOCl 5.25% compared with acrylic resin. Acetal resin showed clinically acceptable (ΔΕ*) whereas acrylic resin unacceptable ones for water and peroxide solutions. The immersion of acetal resin in NaOCl 5.25% showed clinically unacceptable (ΔΕ*) and higher sorption and should be avoided or should be managed with care.     

Modeling of Peptides in Implicit Membrane-Mimetic Media

Abstract

Lipid bilayer plays a crucial role in folding of membrane peptides and their stabilization in the membrane-bound state. Correct treatment of the media effects is thus essential for realistic simulations of peptides in bilayers. Previously (Volynsky et al., 1999), we proposed an efficient solvation model which mimics heterogeneous membrane-water system. The model is based on combined employment of atomic solvation parameters for water and hydrocarbon, which approximate hydrated headgroups and acyl chains of lipids, respectively. In this study, the model is employed in non-restrained Monte Carlo simulations of several peptides: totally apolar 20-residue poly-L-Leu, hydrophobic peptide with polar edges, and strongly amphiphilic pep-tide. The principal goals are: to explore energy landscape of these peptides in membrane; to characterize the structures of low-energy states and their orientations with respect to the bilayer. Simulations were performed starting from different structures (unordered or helical) and orientations. It was found that the membrane environment significantly promotes an α-helical conformation for all the peptides, while their energetically favourable orientations are quite different. Thus, poly-Leu was immobilized inside the membrane, the hydrophobic peptide with polar termini adapted transbilayer orientation, whereas the amphiphilic peptide stayed on the lipid-water interface in peripherial orientation. Energy barriers between different states were characterized. The computational results were compared with the experimental structural data.     

Revising the Absolute Configurations of Coatlines via Density Functional Theory Calculations of Electronic Circular Dichroism Spectra

Coatline A ( 1 ) and α‐epi‐coatline A ( 4 ) co‐occur in the trunk extract of Andira coriacea. Inspection of their chiroptical properties led to intriguing results. After a careful examination of the experimental data used for the previously reported absolute configuration of these compounds, some uncertainties were identified. A combined theoretical approach including conformational analyses and calculation of electronic circular dichroism (ECD) spectra, in addition with experimental data obtained for schoepfin A ( 5 ) and the new schoepfin D ( 6 ) isolated from Senna quinquangulata, allowed the revision of the absolute configuration of coatlines A ( 1 ) and B ( 2 ). Chirality 25:180–184, 2013. © 2012 Wiley Periodicals, Inc.     

Soil nutrients trump intraspecific effects on understory plant communities

Understanding the links between intraspecific genetic variation and patterns of diversity in associated communities has been the primary focus of community genetics or ‘genes-to-ecosystem’ research in ecology. While other ecological factors, such as the abiotic environment, have well-documented influences on communities, the relative contributions of genetic variation versus the environment to species interactions remains poorly explored. In this study, we use a common garden experiment to study a coastal dune plant community dominated by the shrub, Baccharis pilularis, which displays a morphological dimorphism in plant architecture. We found the differences in the understory plant community between erect and prostrate morphs of Baccharis to be statistically significant, but small relative to the impacts of nutrient additions (NPK and C additions), for the richness, cover, and biomass of the understory plant community. There were no significant interactions between Baccharis morphology and nutrient-addition treatments, suggesting the influence of nutrient addition was consistent between erect and prostrate morphs. Moreover, we found no difference in overall plant community composition between Baccharis morphs, while NPK additions led to shifts in understory community composition compared to unfertilized shrubs. In sum, our results indicate that nutrients are the more important factor governing understory plant community structure in a coastal dunes ecosystem followed by intraspecific variation in dominant shrub architecture. Our results address a growing call to understand the extended consequences of intraspecific variation across heterogeneous environments in terrestrial ecosystems.     

Fruit cuticle lipid composition and water loss in a diverse collection of pepper (Capsicum)

Pepper (Capsicum spp.) fruits are covered by a relatively thick coating of cuticle that limits fruit water loss, a trait previously associated with maintenance of postharvest fruit quality during commercial marketing. To shed light on the chemical‐compositional diversity of cuticles in pepper, the fruit cuticles from 50 diverse pepper genotypes from a world collection were screened for both wax and cutin monomer amount and composition. These same genotypes were also screened for fruit water loss rate and this was tested for associations with cuticle composition. Our results revealed an unexpectedly large amount of variation for the fruit cuticle lipids, with a more than 14‐fold range for total wax amounts and a more than 16‐fold range for cutin monomer amounts between the most extreme accessions. Within the major wax constituents fatty acids varied from 1 to 46%, primary alcohols from 2 to 19%, n‐alkanes from 13 to 74% and triterpenoids and sterols from 10 to 77%. Within the cutin monomers, total hexadecanoic acids ranged from 54 to 87%, total octadecanoic acids ranged from 10 to 38% and coumaric acids ranged from 0.2 to 8% of the total. We also observed considerable differences in water loss among the accessions, and unique correlations between water loss and cuticle constituents. The resources described here will be valuable for future studies of the physiological function of fruit cuticle, for the identification of genes and QTLs associated with fruit cuticle synthesis in pepper fruit, and as a starting point for breeding improved fruit quality in pepper.     

Measuring variation in potato roots in both field and glasshouse: the search for useful yield predictors and a simple screen for root traits

Aims

Potatoes have an inadequate rooting system for efficient acquisition of water and minerals and use disproportionate amounts of irrigation and fertilizer. This research determines whether significant variation in rooting characteristics of potato exists, which characters correlate with final yield and whether a simple screen for rooting traits could be developed.

Methods

Twenty-eight genotypes of Solanum tuberosum groups Tuberosum and Phureja were grown in the field; eight replicate blocks to final harvest, while entire root systems were excavated from four blocks. Root classes were categorised and measured. The same measurements were made on these genotypes in the glasshouse, 2 weeks post emergence.

Results

In the field, total root length varied from 40 m to 112 m per plant. Final yield was correlated negatively with basal root specific root length and weakly but positively with total root weight. Solanum tuberosum group Phureja genotypes had more numerous roots and proportionally more basal than stolon roots compared with Solanum tuberosum, group Tuberosum genotypes. There were significant correlations between glasshouse and field measurements.

Conclusions

Our data demonstrate that variability in rooting traits amongst commercially available potato genotypes exists and a robust glasshouse screen has been developed. By measuring potato roots as described in this study, it is now possible to assess rooting traits of large populations of potato genotypes.     

Elucidation of the Structure and Reaction Mechanism of Sorghum Hydroxycinnamoyltransferase and Its Structural Relationship to Other Coenzyme A-Dependent Transferases and Synthases

Hydroxycinnamoyltransferase (HCT) from sorghum (Sorghum bicolor) participates in an early step of the phenylpropanoid pathway, exchanging coenzyme A (CoA) esterified to p-coumaric acid with shikimic or quinic acid as intermediates in the biosynthesis of the monolignols coniferyl alcohol and sinapyl alcohol. In order to elucidate the mode of action of this enzyme, we have determined the crystal structures of SbHCT in its apo-form and ternary complex with shikimate and p-coumaroyl-CoA, which was converted to its product during crystal soaking. The structure revealed the roles of threonine-36, serine-38, tyrosine-40, histidine-162, arginine-371, and threonine-384 in catalysis and specificity. Based on the exact chemistry of p-coumaroyl-CoA and shikimic acid in the active site and an analysis of kinetic and thermodynamic data of the wild type and mutants, we propose a role for histidine-162 and threonine-36 in the catalytic mechanism of HCT. Considering the calorimetric data, substrate binding of SbHCT should occur sequentially, with p-coumaroyl-CoA binding prior to the acyl acceptor molecule. While some HCTs can use both shikimate and quinate as an acyl acceptor, SbHCT displays low activity toward quinate. Comparison of the structure of sorghum HCT with the HCT involved in chlorogenic acid synthesis in coffee (Coffea canephora) revealed many shared features. Taken together, these observations explain how CoA-dependent transferases with similar structural features can participate in different biochemical pathways across species.Lignin is a major structural and protective component of plant cell walls. Lignin exists as a polymer of mainly three hydroxycinnamyl alcohols and related compounds, referred to as monolignols. The most common monolignols are coniferyl, sinapyl, and p-coumaryl alcohol (Ralph et al., 2004; Vanholme et al., 2010). After polymerization, structures derived from those compounds are referred to as guaiacyl, syringyl, and p-hydroxyphenyl subunits, respectively. The specific composition of lignin subunits varies among species, tissues, and developmental stages. Gymnosperm trees produce lignin that is primarily made of guaiacyl subunits, angiosperm trees contain guaiacyl and syringyl subunits, whereas grasses contain guaiacyl and syringyl subunits with small amounts (approximately 5%) of p-hydroxyphenyl residues. This observed variation in subunit composition across species may reflect the heterogeneity in substrate specificity and kinetic parameters among various monolignol biosynthetic enzymes (Weng et al., 2008).Biosynthesis of the monolignols occurs via the phenylpropanoid pathway using Phe precursors (Vanholme et al., 2010). Phe ammonia lyase, cinnamate-4-hydroxylase, and 4-coumarate coenzyme A (CoA) ligase (4CL) generate p-coumaroyl-CoA from Phe (Vanholme et al., 2010). Grasses can bypass cinnamate-4-hydroxylase by using Tyr as a substrate for Phe ammonia lyase (Neish, 1961; Rösler et al., 1997). The hydroxycinnamoyltransferase (HCT) enzymes exchange the CoA functionality esterified to p-coumaric acid with shikimic or quinic acid to allow for the subsequent conversion of the p-coumaroyl moiety to a caffeoyl moiety by p-coumarate-3′-hydroxylase (C3′H). The hydroxycinnamoyl-CoA shikimate hydroxycinnamoyltransferases (HSTs) exhibit preference for shikimate, whereas the hydroxycinnamoyl-CoA quinate hydroxycinnamoyltransferases prefer quinate as a substrate (Sander and Petersen, 2011). Subsequent reactions ultimately lead to coniferyl and sinapyl alcohol via reduction of the γ-carbon on the propane side chain and substitution of the C3 and C5 positions of the phenol ring (Boerjan et al., 2003).Sorghum (Sorghum bicolor) is an attractive bioenergy crop with typical dry biomass yields between 20 and 25 Mg ha⁻¹ and yields as high as 40 Mg ha⁻¹ possible under optimal conditions (Venuto and Kindiger, 2008). Moreover, sorghum utilizes nitrogen-based fertilizer more efficiently than maize (Zea mays) and sugarcane (Saccharum officinarum), leading to less groundwater contamination and lower CO₂ emission (Propheter and Staggenborg, 2010; Wortmann and Regassa, 2011). Overall, sorghum has a higher sugar yield potential per land area and requires less water for growth than maize, allowing it to grow in a more diverse range of environments (Saballos, 2008). The sorghum genome sequence has been released (Paterson et al., 2009), and Targeting Induced Local Lesions in Genomes populations exist (Xin et al., 2008) in which various cell wall mutants have been identified (Sattler et al., 2012; Vermerris and Saballos, 2012).A detailed understanding of the catalytic mechanism of phenylpropanoid-related enzymes will enable the targeted modification of lignin subunit composition. The presence of lignin poses a major obstacle to the production of biofuels and chemicals from lignocellulosic biomass, because of its ability to hinder the activity of enzymes required to degrade cellulose to sugars that can be fermented for ethanol production (Yang and Wyman, 2004; Berlin et al., 2006). Genetic modification of plant cell wall composition, especially lignin content and subunit composition, has been shown to improve biomass conversion to fermentable sugars (Chen and Dixon, 2007; Vermerris et al., 2007; Jung et al., 2012). In particular, HCT silencing in Arabidopsis (Arabidopsis thaliana) causes an accumulation of p-hydroxyphenyl residues in the lignin and decreased content of guaiacyl and syringyl residues, leading to a dwarf phenotype (Li et al., 2010). Down-regulation of HCT has also been shown to result in decreased plant growth in alfalfa (Medicago sativa; Shadle et al., 2007). Concomitantly, ruminant digestibility and the yield of fermentable sugars following enzymatic saccharification increased (Chen and Dixon, 2007; Shadle et al., 2007). Reduced HCT activity may alter cell wall polymer interactions and allow better access of cellulolytic enzymes to the cellulose. Therefore, it has the potential to reduce the energy and processing costs associated with the conversion of biomass to fuels and chemicals. However fine-tuning will be necessary to limit the negative impacts on plant growth, which will require a detailed understanding of the catalytic mechanism of HCT.Given the difference in lignin subunit composition among different species and the prominence of grasses among dedicated bioenergy crops, we have focused on elucidating the crystal structure and activity of monolignol-related enzymes of sorghum, starting with the HST-like HCT. HCT belongs to the BAHD superfamily of plant-specific acyl-CoA-dependent acyltransferases (Ma et al., 2005; D’Auria, 2006). However, the BAHD superfamily has functionally and structurally diverse members that frequently possess little (as low as 10%) sequence identity among them (St-Pierre and Luca, 2000). Recent studies led to the crystal structure of the HST-like HCT from robusta coffee (Coffea canephora), an angiosperm dicot with a binding pocket elucidated by molecular docking and mutagenesis (Lallemand et al., 2012). In this report, we present the three-dimensional structures of HCT in its apo-form and ternary complex, supplemented by mutagenic studies to elucidate its reaction mechanism and structural relationship to other members in this growing functional class.     

Naturally Acquired Picornavirus Infections in Primates at the Dhaka Zoo

The conditions in densely populated Bangladesh favor picornavirus transmission, resulting in a high rate of infection in the human population. Data suggest that nonhuman primates (NHP) may play a role in the maintenance and transmission of diverse picornaviruses in Bangladesh. At the Dhaka Zoo, multiple NHP species are caged in close proximity. Their proximity to other species and to humans, both zoo workers and visitors, provides the potential for cross-species transmission. To investigate possible interspecies and intraspecies transmission of picornaviruses among NHP, we collected fecal specimens from nine NHP taxa at the Dhaka Zoo at three time points, August 2007, January 2008, and June 2008. Specimens were screened using real-time PCR for the genera Enterovirus, Parechovirus, and Sapelovirus, and positive samples were typed by VP1 sequencing. Fifty-two picornaviruses comprising 10 distinct serotypes were detected in 83 fecal samples. Four of these serotypes, simian virus 19 (SV19), baboon enterovirus (BaEV), enterovirus 112 (EV112), and EV115, have been solely associated with infection in NHP. EV112, EV115, and SV19 accounted for 88% of all picornaviruses detected. Over 80% of samples from cages housing rhesus macaques, olive baboons, or hamadryas baboons were positive for a picornavirus, while no picornaviruses were detected in samples from capped langurs or vervet monkeys. In contrast to our findings among synanthropic NHP in Bangladesh where 100% of the picornaviruses detected were of human serotypes, in the zoo population, only 15% of picornaviruses detected in NHP were of human origin. Specific serotypes tended to persist over time, suggesting either persistent infection of individuals or cycles of reinfection.