A genetic analysis of cell culture traits in tomato

Summary Tomato genotypes superior in regenerating plants from protoplast and callus cultures were obtained by transferring regeneration capacity from Lycopersicon peruvianum into L. esculentum by classical breeding. The genetics of regeneration and callus growth have been studied in selfed and backcross progenies of a selected plant (MsK93) which has 25% L. peruvianum in its ancestry. Segregation data showed that the favourable cell culture traits of L. peruvianum are dominant. Regeneration capacity from established callus cultures was controlled by two dominant genes. Callus growth on primary expiants, callus growth of established cultures and shoot regeneration from explants had high heritabilities (0.47, 0.78, 0.87, respectively). Callus growth and regeneration capacity were not correlated within the populations studied.     

An Ancient Divide in a Contiguous Rainforest: Endemic Earthworms in the Australian Wet Tropics

Understanding the factors that shape current species diversity is a fundamental aim of ecology and evolutionary biology. The Australian Wet Tropics (AWT) are a system in which much is known about how the rainforests and the rainforest-dependent organisms reacted to late Pleistocene climate changes, but less is known about how events deeper in time shaped speciation and extinction in this highly endemic biota. We estimate the phylogeny of a species-rich endemic genus of earthworms (Terrisswalkerius) from the region. Using DEC and DIVA historical biogeography methods we find a strong signal of vicariance among known biogeographical sub-regions across the whole phylogeny, congruent with the phylogeography of less diverse vertebrate groups. Absolute dating estimates, in conjunction with relative ages of major biogeographic disjunctions across Australia, indicate that diversification in Terrisswalkerius dates back before the mid-Miocene shift towards aridification, into the Paleogene era of isolation of mesothermal Gondwanan Australia. For the Queensland endemic Terrisswalkerius earthworms, the AWT have acted as both a museum of biological diversity and as the setting for continuing geographically structured diversification. These results suggest that past events affecting organismal diversification can be concordant across phylogeographic to phylogenetic levels and emphasize the value of multi-scale analysis, from intra- to interspecies, for understanding the broad-scale processes that have shaped geographic diversity.     

Anionic Lipids Allosterically Modulate Multiple Nicotinic Acetylcholine Receptor Conformational Equilibria

Anionic lipids influence the ability of the nicotinic acetylcholine receptor to gate open in response to neurotransmitter binding, but the underlying mechanisms are poorly understood. We show here that anionic lipids with relatively small headgroups, and thus the greatest ability to influence lipid packing/bilayer physical properties, are the most effective at stabilizing an agonist-activatable receptor. The differing abilities of anionic lipids to stabilize an activatable receptor stem from differing abilities to preferentially favor resting over both uncoupled and desensitized conformations. Anionic lipids thus modulate multiple acetylcholine receptor conformational equilibria. Our data suggest that both lipids and membrane physical properties act as classic allosteric modulators influencing function by interacting with and thus preferentially stabilizing different native acetylcholine receptor conformational states.     

A Lipid-dependent Uncoupled Conformation of the Acetylcholine Receptor

Lipids influence the ability of Cys-loop receptors to gate open in response to neurotransmitter binding, but the underlying mechanisms are poorly understood. With the nicotinic acetylcholine receptor (nAChR) from Torpedo, current models suggest that lipids modulate the natural equilibrium between resting and desensitized conformations. We show that the lipid-inactivated nAChR is not desensitized, instead it adopts a novel conformation where the allosteric coupling between its neurotransmitter-binding sites and transmembrane pore is lost. The uncoupling is accompanied by an unmasking of previously buried residues, suggesting weakened association between structurally intact agonist-binding and transmembrane domains. These data combined with the extensive literature on Cys-loop receptor-lipid interactions suggest that the M4 transmembrane helix plays a key role as a lipid-sensor, translating bilayer properties into altered nAChR function.     

Body size variation and caste ratios in geographically distinct populations of the invasive big‐headed ant,Pheidole megacephala (Hymenoptera: Formicidae)

Body size is an important life history trait that can evolve rapidly as a result of how species interact with each other and their environment. Invasive species often encounter vastly different ecological conditions throughout their introduced range that can influence relative investment in growth, reproduction and defence among populations. In this study, we quantified variation in worker size, morphology and proportion of majors among five populations of a worldwide invasive species, the big‐headed ant, Pheidole megacephala (Fabricius). The sampled populations differed in ant community composition, allowing us to examine if P. megacephala invests differently in the size and number of majors based on the local ant fauna. We also used genetic data to determine if these populations of P. megacephala represented cryptic species or if morphological differences could be attributed to change following introduction. We found significant variation in worker mass among the populations. Both major and minor workers were largest in Australia, where the ant fauna was most diverse, and minor workers were smallest in Hawaii and Mauritius, where P. megacephala interacted with few to no other ants. We also found differences in major and minor worker morphology among populations. Majors from Mauritius had significantly larger heads (width and length) relative to whole body size than those from Hawaii and Florida. Minors had longer heads and hind tibias in South Africa compared with populations from Australia, Hawaii and Florida. The proportion of majors did not differ among populations, suggesting that these populations may not be subject to trade‐offs in investment in major size versus number. Our molecular data place all samples within the same clade, supporting that these morphologically different populations represent the same species. These results suggest that the variation in shape and morphology of major and minor workers may therefore be the result of rapid adaptation or plastic responses to local conditions. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 423–438.     

Multiplexed microsphere diagnostic tools in gene expression applications: factors and futures

Microarrays have received significant attention in recent years as scientists have firstly identified factors that can produce reduced confidence in gene expression data obtained on these platforms, and secondly sought to establish laboratory practices and a set of standards by which data are reported with integrity. Microsphere-based assays represent a new generation of diagnostics in this field capable of providing substantial quantitative and qualitative information from gene expression profiling. However, for gene expression profiling, this type of platform is still in the demonstration phase, with issues arising from comparative studies in the literature not yet identified. It is desirable to identify potential parameters that are established as important in controlling the information derived from microsphere-based hybridizations to quantify gene expression. As these evolve, a standard set of parameters will be established that are required to be provided when data are submitted for publication. Here we initiate this process by identifying a number of parameters we have found to be important in microsphere-based assays designed for the quantification of low abundant genes which are variable between studies.     

Carbohydrate liquid crystals: synthesis and characterisation of the methyl-6-O-(n-acyl)-α-D-glucopyranosides

Seven members of the methyl-6-O-(n-acyl)-α-d-glucopyranosides have been synthesised and their transitional properties determined. The undecanoyl and octadecanoyl members do not exhibit liquid crystallinity while the members having chain lengths between dodecanoyl and hexadecanoyl exhibit a monotropic smectic A phase. Variable temperature infrared spectroscopy reveals that the hydrogen bonding within the system shows a marked change at the melting point but apparently no change at the smectic A-isotropic transition. This observation is interpreted in terms of Goodby's model for the smectic A phase in which the carbohydrate moieties are located at the centre of the smectic bilayer and assuming that hydrogen bonded aggregates persist into the isotropic phase. Within this framework, the unusually low values of the entropy change associated with the smectic A-isotropic transition may also be accounted for.     

Validation of alternative methods for the analysis of drinking water and their application to Escherichia coli

In Europe, the Drinking Water Directive of the European Commission indicates which methods (most of which are CEN/ISO-standardized methods) should be used for the analysis of microbiological parameters (European Commission, Environment, Council Directive 98/83/EC of 3 November 1998). According to the Directive, alternative methods “may be used, providing it can be demonstrated that the results obtained are at least as reliable as those produced by the methods specified.” The prerequisite for the routine use of any alternative method is to provide evidence that this method performs equivalently to the corresponding reference method. In this respect, the ISO 16140 standard (ISO, ISO 16140. Microbiology of Food and Animal Feeding Stuffs—Protocol for the Validation of Alternative Methods, 2003) represents a key issue in generating such a procedure based on an interlaboratory study. A new statistical tool, called the accuracy profile, has been developed to better interpret the data. The study presented here is based upon the enumeration of Escherichia coli bacteria in water. The reference method may require up to 72 h to provide a confirmed result. The aim of this publication is to present data for an alternative method by which results can be obtained in 18 h (Colilert-18/Quanti-Tray) based upon defined substrate technology (DST). The accuracy profile is a statistical and graphical decision-making tool and consists of simultaneously combining, in a single graphic, β expectation tolerance intervals (β-ETIs) and acceptability limits (λ). The study presents the validation criteria calculated at the three levels of contamination used in the trial for a β equal to 80% and a λ equal to ±0.3 and combines the accuracy profiles of Escherichia coli for a λ of ±0.3 log₁₀ unit/100 ml, a λ of ±0.4 log₁₀ unit/100 ml, and a β of 80% or 90%. Several interesting conclusions can be drawn from these data. The accuracy profile method has been applied to the validation of the Colilert-18/Quanti-Tray method against reference method ISO 9308-1 (ISO, ISO 9308-1. Water Quality—Detection and Enumeration of Escherichia coli and Coliform Bacteria. Part 1. Membrane Filtration Method, 2000), using a β of 80% and a λ of 0.4; the alternative method can be validated between 1.00 and 2.05 log₁₀ units/100 ml, equivalent to 10 to 112 CFU/100 ml.