Variability within a pea core collection of LEAM and HSP22, two mitochondrial seed proteins involved in stress tolerance

LEAM, a late embryogenesis abundant protein, and HSP22, a small heat shock protein, were shown to accumulate in the mitochondria during pea (Pisum sativum L.) seed development, where they are expected to contribute to desiccation tolerance. Here, their expression was examined in seeds of 89 pea genotypes by Western blot analysis. All genotypes expressed LEAM and HSP22 in similar amounts. In contrast with HSP22, LEAM displayed different isoforms according to apparent molecular mass. Each of the 89 genotypes harboured a single LEAM isoform. Genomic and RT‐PCR analysis revealed four LEAM genes differing by a small variable indel in the coding region. These variations were consistent with the apparent molecular mass of each isoform. Indels, which occurred in repeated domains, did not alter the main properties of LEAM. Structural modelling indicated that the class A α‐helix structure, which allows interactions with the mitochondrial inner membrane in the dry state, was preserved in all isoforms, suggesting functionality is maintained. The overall results point out the essential character of LEAM and HSP22 in pea seeds. LEAM variability is discussed in terms of pea breeding history as well as LEA gene evolution mechanisms.     

New replication mutant pnh602 and its relationship to plasmid pAS3, another deletion derivative of plasmid R6K

A stable deletion derivative pNH602 was obtained when the recently described higher-copy-number point mutant pNH601 of plasmid R6K was introduced to a minicells-producing strain of Escherichia coli. The size of plasmid pNH602 is 18.8 Mg/mol as determined by electron microscopy. The 7.2 Mg/mol fragment of R6K genome missing in pNH602 carries the Smr-determinant and the region finO and, according to the results of restriction analysis, it includes one EcoRI site. With its radioisotopically determined 33 copies of pNH602 per E. coli K-12 chromosome (npc), representing a 23% increase of the point mutant pNH601 and 150% enhancement of R6K npc, plasmid pNH602 differs from another closely related R6K deletion derivative pAS3 of the same size which exhibits only 20 npc. Both pNH602 and pAS3 plasmids are conjugative.     

Cicada ear geometry: species and sex effects

Many insect species rely on their sense of audition to find a mate, to localize prey or to escape from a predator. Cicadas are particularly known for their loud call and the conspicuous tympanal hearing system located in their abdomen. The vibration pattern of the tympanal membrane (TM) has been investigated recently revealing mechanical properties specific to species and sex. Although TM size and shape is likely to affect these patterns, the geometry of the cicada ear has never been examined per se. Focusing on three Mediterranean cicada species, namely Cicadatra atra, Cicada orni and Lyristes plebejus, we investigated the structure of TM shape variation at two levels, within and across species. Applying an elliptic Fourier analysis to the outlines of both male and female TMs, we estimated sexual dimorphism and species effects. Cicadatra atra showed a large TM compared with its small size, probably as a result of selective constraints related to the role of the TM in sound production. Sexual dimorphism seemed to be greater than interspecific variation, indicating that constraints operating on sex might be more selective than those acting on species identification. In addition, C. orni appeared to be significantly different from the two other species. This morphological peculiarity could be related to the unique vibrational pattern of its membrane. This would establish for the first time a direct link between the shape and mechanism of a hearing organ. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 922–934.     

Theoretical habitat templets, species traits, and species richness: aquatic macrophytes in the Upper Rhône River and its floodplain

• 1 The objective of this study, which is based on forty-two species of hydrophytes and helophytes, is to investigate: (i) relationships among species traits; (ii) habitat utilization by species; (iii) the relationship between species traits and habitat utilization; (iv) trends in species traits in the framework of spatial–temporal habitat variability, and if trends match predictions from the river habitat templet; and (v) trends in species richness in the framework of spatial–temporal habitat variability, and if trends match predictions of the patch dynamics concept.
• 2 Two data sets were used for this analysis: species traits (mainly reproductive and morphological characteristics) were documented from the literature; and species distribution across eight habitat types was from field surveys conducted in the floodplain of the Upper Rhone River, France. This information was structured by a fuzzy coding technique and analysed by ordination methods.
• 3 Several species traits, which are related to disturbances and reflect resistance (e.g. attachment to soil or substrate) or resilience (e.g. potential for regeneration of an individual), are closely related for aquatic macrophytes.
• 4 Habitat utilization by aquatic macrophytes separates the habitat types along a gradient of connectivity with the main channel, which corresponds to a gradient in flood disturbance frequency and the permanence of the different water-bodies.
• 5 The relationship between species traits and habitat utilization is highly significant, indicating that a particular set of habitat types is used by taxa with a particular set of species trait modalities.
• 6 Observations in one habitat templet (in which scaling of the templet is primarily based on water level fluctuations for the temporal variability axis and on substrate characteristics for the spatial variability axis) generally do not support predictions on trends in species traits but do support predictions on trends in species richness.
• 7 Observations in an alternative habitat templet (in which scaling of the templet is based on frequency of flood scouring for the temporal variability axis and on heterogeneity of the substrate for the spatial variability axis) support theoretical predictions on trends for about half of the species traits for which predictions were available. However, trends in species richness in this alternative habitat templet are only partly in agreement with predictions.

     

Palaeohistology of the bones of pterosaurs (Reptilia: Archosauria): anatomy, ontogeny, and biomechanical implications

Thin sections from long bones of specimens representing pterosaurs ranging from the Early Jurassic to the latest Cretaceous provide a profile of bone histology across a range of sizes, skeletal elements, growth stages, and phylogenetic positions. Most pterosaur bone is fibro-lamellar, organized in an unusual way that suggests high growth rates through ontogeny. Fibro-lamellar deposits are finished by a relatively abrupt deceleration or cessation of growth represented by lamellar, poorly vascularized subperiosteal bone in what appear to be adults. Pterosaurs had the thinnest bone walls of any tetrapods; they complemented high rates of periosteal deposition with almost equally high rates of endosteal erosion. Pterosaurs show a great variety of histologic features that include articular calcified cartilage, sub-chondral bone plates, trabecular bone struts and related internal supports, and secondary deposition and remodeling of bone. They remodeled their bones internally by (1) depositing endosteal bone coatings on the inner cortex and over struts of pre-existing internal bone, (2) secondarily filling bone spaces, and (3) Haversian reworking. The construction of these struts reflects both developmental patterns of bone construction and biomechanical function. Alternating plywood-like layers of bone, heretofore undescribed in tetrapods, provided strength, as did the obliquely oriented system of reticular blood vessels in the bones. The distribution and ontogenetic features of pterosaur bone tissues, when combined with other evidence, suggest generally high growth rates, high metabolic levels, altricial birth, and extended parental care.     

Fermentation characterization and flux analysis of recombinant strains of Clostridium acetobutylicum with an inactivated solR gene

The effect of solR inactivation on the metabolism of Clostridium acetobutylicum was examined using fermentation characterization and metabolic flux analysis. The solR-inactivated strain (SolRH) of this study had a higher rate of glucose utilization and produced higher solvent concentrations (by 25%, 14%, and 81%, respectively, for butanol, acetone, and ethanol) compared to the wild type. Strain SolRH(pTAAD), carrying a plasmid-encoded copy of the bifunctional alcohol/aldehyde dehydrogenase gene (aad) used in butanol production, produced even higher concentrations of solvents (by 21%, 45%, and 62%, respectively, for butanol, acetone, and ethanol) than strain SolRH. Clarithromycin used for strain SolRH maintenance during SolRH(pTAAD) fermentations did not alter product formation; however, tetracycline used for pTAAD maintenance resulted in 90% lower solvent production. Journal of Industrial Microbiology & Biotechnology (2001) 27, 322–328. Received 12 September 2000/ Accepted in revised form 21 July 2001     

Accumulation of polyunsaturated fatty acids by cladocerans: effects of taxonomy,temperature and food

1. Zooplankton are important in transferring dietary nutrients, including polyunsaturated fatty acids (PUFA), up through aquatic food webs. 2. We tested the hypothesis that the taxonomic composition of zooplankton affects the retention and subsequent transfer of PUFA from upwards through the food web. Using laboratory experiments, we investigated dietary PUFA accumulation and bioconversion capacities of six cladoceran species (Ceriodaphnia sp., Daphnia longispina, Daphnia magna, Daphnia pulex, Scapholeberis mucronata and Simocephalus vetulus) fed on two diets (Scenedesmus obliquus and Cryptomonas sp.) that differed in their PUFA profiles. We performed experiments at two different temperatures (14 and 20 °C) to assess the role of temperature in the trophic transfer of PUFA. 3. There was little variation in the concentrations of PUFA in these cladocerans which were controlled by dietary PUFA supply. Moreover, as expected, the concentrations of PUFA in all cladoceran species were higher at low temperature. 4. However, even if the composition of PUFA in the cladoceran species generally corresponded to that in their diet, preferential accumulation of some PUFA was recorded in all these taxa. When fed on a highly unsaturated fatty acid‐deficient diet, all the cladocerans showed some ability to convert C18‐PUFA into arachidonic acid and eicosapentaenoic acid. Interspecific variation in the ability to accumulate and bioconvert PUFA in cladocerans was more pronounced at low temperature (14 °C) for both diets. 5. Our results strongly suggest that in heterogeneous habitats with food partitioning between co‐existing cladocerans, foraging behaviour may affect the transfer of PUFA more strongly than interspecific variation in accumulating and/or bioconverting dietary PUFA.     

Short‐term effects of CO2 and O2 on citrate metabolism in illuminated leaves

Although there is now a considerable literature on the inhibition of leaf respiration (CO₂ evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO₂ and O₂ mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.) under different CO₂/O₂ conditions. Gas exchange coupled to online isotopic analysis showed that CO₂ evolved by leaves in the light came from ‘old’ carbon skeletons and there was a slight decrease in ¹³C natural abundance when [CO₂] increased. This suggested the involvement of enzymatic steps fractionating more strongly against ¹³C and thus increasingly limiting for the metabolic respiratory flux as [CO₂] increased. Isotopic labelling with ¹³C₂‐2,4‐citrate lead to ¹³C‐enriched Glu and 2‐oxoglutarate (2OG), clearly demonstrating poor metabolism of citrate by the TCAP. There was a clear relationship between the ribulose‐1,5‐bisphosphate oxygenation‐to‐carboxylation ratio (v_o/v_c) and the ¹³C commitment to 2OG, demonstrating that 2OG and Glu synthesis via the TCAP is positively influenced by photorespiration.     

Physical forces constrain the depth distribution of the abundant native mussel Elliptio complanata in lakes

1. Unionid mussels often account for a large portion of benthic biomass and contribute to nutrient cycling and sediment processes, but are thought to be limited to shallow areas (<2–3 m). 2. The depth distribution and body size of Elliptio complanata were compared in seven Canadian Shield lake basins of different sizes to test what factors determine the upper and lower limit of their depth range. Specifically, I tested whether (i) the upper range of their distribution is limited by exposure to winds and wave action and (ii) the lower range of their distribution is limited by the depth of the thermocline or by the boundary of mud deposition. 3. The average depth distribution of E. complanata shifted to greater depths in larger lake basins. When comparing individual transects, maximum mussel density was found deeper at more exposed sites. Mussel size decreased with increasing depth and was larger, on average, in larger lake basins. These results suggest that physical forces limit the upper range of mussel distribution in lakes. 4. The maximum depth at which mussels were found in different lakes was closely related to thermocline depth. However, mussels were commonly observed below the predicted depth of the mud deposition boundary. The thermocline limits the lower range of mussel distribution in lakes, probably by limiting food availability and by determining water temperature. Substratum type does not limit the lower distribution of mussels. 5. These results suggest that unionid mussels are present in the deeper parts of the littoral zone, especially in large lakes. Therefore, comparisons of mussel populations between sites and between lakes would be biased unless the full depth distribution of these mussels is considered. These results also suggest that long‐term changes in the thermal structure of lakes could affect the range of unionid mussel populations and their functional role in littoral ecosystems.     

Host preferences of Palaearctic Culicoides biting midges: implications for transmission of orbiviruses

Feeding success depends on host availability, host defensive reactions and host preferences. Host choice is a critical determinant of the intensity at which pathogens are transmitted. The aim of the current study was to describe host preferences of Palaearctic Culicoides species (Diptera: Ceratopogonidae) Latreille using traps baited with the five different host species of poultry, horse, cattle, sheep and goat. Collections were carried out nightly in July and August 2009 in western France with three replicates of a 5 × 5 randomized Latin square (five sites, five hosts). Moreover, an ultraviolet (UV) light/suction trap was operated during host‐baited collections to correlate Culicoides biting rates and UV light/suction trap catches. A total of 660 Culicoides belonging to 12 species, but comprised mainly of Culicoides scoticus Downes and Kettle, Culicoides dewulfi Goetghebuer and Culicoides obsoletus Meigen, were collected on animal baits. Abundance was highest for the horse, which accounted for 95% of all Culicoides caught, representing 10 species. The horse, the largest bait, was the most attractive host, even when abundance data were corrected by weight, body surface or Kleiber's scaling factor. Culicoides obsoletus was the only dominant species attracted by birds. Both C. scoticus and C. dewulfi were collected mainly from the upper body of the horse. Finally, the quantification of host preferences allows for discussion of implications for the transmission of Culicoides‐borne pathogens such as bluetongue virus.