The ecoresponsive genome of Daphnia pulex

We describe the draft genome of the microcrustacean Daphnia pulex, which is only 200 megabases and contains at least 30,907 genes. The high gene count is a consequence of an elevated rate of gene duplication resulting in tandem gene clusters. More than a third of Daphnia's genes have no detectable homologs in any other available proteome, and the most amplified gene families are specific to the Daphnia lineage. The coexpansion of gene families interacting within metabolic pathways suggests that the maintenance of duplicated genes is not random, and the analysis of gene expression under different environmental conditions reveals that numerous paralogs acquire divergent expression patterns soon after duplication. Daphnia-specific genes, including many additional loci within sequenced regions that are otherwise devoid of annotations, are the most responsive genes to ecological challenges.     

Sub-irrigation in wetland agriculture

Much has been written about the chinampas of central Mexico. One of the commonly repeated themes is that these wetland fields were self-irrigated from below in a process known as sub-irrigation. According to this model, water infiltrates the planting platforms from adjacent canals and then rises to the root zone by capillary action. Thus, chinampas are thought to have needed little supplemental irrigation, and produced dependable and high yields. Here I report the results of field and lab studies of soils of 10 chinampas in the region east of Xochimilco, in the Mexican Federal District. These interpretations are combined with discussion of maize rooting tendencies, regional rainfall patterns, and the presence of willow tree roots in chinampa soils. I also consider whether farmers strive to create and maintain optimum field morphologies for subirrigation when faced with both flood and drought risk, and when manual irrigation is aready option. I conclude that while sub-irrigation is possible under certain combinations of field morphology, crop type, and soil properties, it was a relatively minor factor in the overall decision-making process of past chinampa farmers, and should not be a major determinant of future planning for chinampa preservation or reconstruction. Furthermore, sub-irrigation must be modeled carefully in relation to soil properties, croptypes, and seasonality if it is to beconsidered a significant function of wetland fields in any context.     

Characterization of proanthocyanidin in hot water extract isolated from <Emphasis Type="Italic">Pinus radiata</Emphasis> bark

Proanthocyanidins (PAs) in the hot water extract prepared from Pinus radiata bark were isolated by a Sephadex LH-20 chromatography. The PAs were characterized using UV/Visible, FT-IR and ¹³C nuclear magnetic resonance (NMR) spectroscopic techniques, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS), and gel permeation chromatography (GPC) analysis. Bate-Smith acidic alcoholysis and FT-IR spectrum of the PAs indicated the predominant presence of the procyanidin (PC) structure. The ¹³C NMR spectrum revealed that the PAs comprise PC (94%) together with a small amount of prodelphinidin (PD, 6%), and also that they contain the higher trans configuration rather than the cis configuration of C2–C3. The MALDI-TOF MS results obviously proved the presence of PD units, but the maximum degree of polymerization (DP) was limited to octamer. The average molar mass (Mw, Mn), polydispersity (Mw/Mn), and DP of the pine bark PAs were 3,800 (Mw), 1,200 (Mn), 3.2, and 13, respectively.     

Adsorption of metal and uranyl ions onto amidoximated Pinus densiflora bark

Pine (Pinus densiflora) bark was chemically modified by grafting with acrylonitrile (AN) through Fenton reaction and conversion of the cyano group to an amidoxime group by reaction with hydroxylamine. Treatments of pine bark with 160 mM H₂O₂ at 40°C yielded ~70% grafting in 6-h reaction. After alkali hydrolysis of amidoximated pine bark (AOPB), its adsorption capacity (q _e) for copper ions was largely increased from 0.5 to 1.8 mmol/g. Adsorption of the hydrolyzed AOPB (HAOPB) followed the pseudo-second-order kinetic model. Among the metal ions tested, the order of adsorption capacity (q _e) predicted by the kinetic model at equilibrium time was Hg²⁺ > UO₂ ²⁺ > Cd²⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺. The adsorption process was pH-dependent, and the adsorption equilibrium was observed in the pH range of 6–7 for all the metal ions. Even though pine bark is a good adsorbent for Hg²⁺ and UO₂ ²⁺ ions, it had a poor affinity for the other ions tested. It was obviously found that HAOPB had very high adsorption abilities for heavy metal and uranyl ions.     

Effects of mutations in Drosophila nicotinic acetylcholine receptor subunits on sensitivity to insecticides targeting nicotinic acetylcholine receptors

Several strains of Drosophila melanogaster possess mutant alleles in nicotinic acetylcholine receptor (nAChR) subunits, Dα1 and Dβ2 that confer resistance to neonicotinoids such as imidacloprid and nitenpyram, and Dα6, that confers resistance to spinosyns. These mutant strains were bioassayed with a selected set of nAChR active insecticides including neonicotinoids, spinosad, and sulfoxaflor, a new sulfoximine insecticide. All of the neonicotinoids examined, except dinotefuran showed reduced insecticidal efficacy on larvae of the Dα1 mutant, suggesting that this subunit may be important in the action of these insecticides. All of the neonicotinoids, including dinotefuran, showed reduced insecticidal efficacy on larvae possessing the Dβ2 mutation. A similar pattern of broad neonicotinoid resistance to that of Dβ2 alone was also observed for larvae with both the mutations (Dα1 + Dβ2). The Dβ2 mutation exhibited a lower level of cross-resistance to sulfoxaflor (<3-fold) than to any of the neonicotinoids (>13-fold). In contrast, there was no cross-resistance for any of the neonicotinoids or sulfoxaflor in adult flies with the Dα6 mutation, which confers high levels of resistance to spinosad. Thus in the D. melanogaster strains studied, target site resistance observed for the neonicotinoids and the spinosyns does not translate directly to resistance towards sulfoxaflor.     

Comparison of shear bonding strength for two different etching systems in canine and human dentin

Canine dentin has increased size and number of dentinal tubules compared to human dentin. With less intertubular surface area for bonding to composite material in dog teeth, bonding shear strength may be affected negatively. This study was designed to compare the shear bonding strength of canine and human dentin. It also compared bond strength of two different acid etch systems when used with the same composite resin. The shear bond strength of composite cylinders to dentin was measured in 30 extracted canine cuspid teeth and a similar number of human molar teeth. Shear bond strength was 40% greater for human compared with canine dentin. This significantly different (P < 0.05) result validates the hypothesis that dentin bond strength is positively correlated with the area of intertubular dentin. Results also indicated that shear bond strength was greater in the self-etching bond system compared with the etch and rinse system, although this difference was not significant.     

Biological Assay for Compost Quality

A plant biological assay or bioassay for determining compost quality and/or maturity has received attention over the past two decades. However, no universal acceptance for compost quality is evident and cress, which was first reported to be used as a plant bioassay, is still the most commonly used. Furthermore, there is evidence indicating that cress is not sensitive enough to distinguish between mature and immature composts. Fourteen seed propagated species were surveyed to see if one or more would be useful as a bioassay for compost quality. The study confirmed that cress is a less sensitive indicator than several species, for example, lettuce, carrot or Chinese cabbage. Amaranthus tricolor was identified as a potential sensitive indicator species since it did not germinate in an immature compost extract. When the compost extract was diluted, the germination index was linear with extract concentration. While cress responded by differences in root growth, amaranthus responded by reduced germination and root growth which gave it a more definitive response. The study concluded that most of the species, including the commonly used cress, are not sensitive enough to detect differences between mature and immature composts. However, Chinese cabbage appears to be the best of the commonly used assay plants. Amaranthus' potential as a sensitive compost maturity indicator was discovered and more studies are needed to confirm this finding.