Diversity, loss, and gain of malaria parasites in a globally invasive bird

Invasive species can displace natives, and thus identifying the traits that make aliens successful is crucial for predicting and preventing biodiversity loss. Pathogens may play an important role in the invasive process, facilitating colonization of their hosts in new continents and islands. According to the Novel Weapon Hypothesis, colonizers may out-compete local native species by bringing with them novel pathogens to which native species are not adapted. In contrast, the Enemy Release Hypothesis suggests that flourishing colonizers are successful because they have left their pathogens behind. To assess the role of avian malaria and related haemosporidian parasites in the global spread of a common invasive bird, we examined the prevalence and genetic diversity of haemosporidian parasites (order Haemosporida, genera Plasmodium and Haemoproteus) infecting house sparrows (Passer domesticus). We sampled house sparrows (N = 1820) from 58 locations on 6 continents. All the samples were tested using PCR-based methods; blood films from the PCR-positive birds were examined microscopically to identify parasite species. The results show that haemosporidian parasites in the house sparrows'' native range are replaced by species from local host-generalist parasite fauna in the alien environments of North and South America. Furthermore, sparrows in colonized regions displayed a lower diversity and prevalence of parasite infections. Because the house sparrow lost its native parasites when colonizing the American continents, the release from these natural enemies may have facilitated its invasion in the last two centuries. Our findings therefore reject the Novel Weapon Hypothesis and are concordant with the Enemy Release Hypothesis.     

Lunachloris lukesovae gen. et sp. nov. (Trebouxiophyceae,Chlorophyta), a novel coccoid green alga isolated from soil in South Bohemia,Czech Republic

Culture collections of microorganisms can still hold undiscovered biodiversity; with molecular techniques, considerable progress has been made in characterizing microalgae which were isolated in the past and misidentified due to a lack of morphological features. However, many strains are still awaiting taxonomic reassessment. Here we analysed the phylogenetic position, morphology and ultrastructure of the strain CCALA 307 previously identified as Coccomyxa cf. gloeobotrydiformis Reysigl isolated in 1987 from field soil in South Bohemia, Czech Republic. Molecular phylogenetic analyses based on SSU rDNA and the plastid rbcL gene revealed that the strain CCALA 307 formed a distinct sister lineage to Neocystis and Prasiola clades within the Trebouxiophyceae. We describe this strain as a new genus and species, Lunachloris lukesovae. Multiple conserved nucleotide positions identified in the secondary structures of the highly variable ITS2 rDNA barcoding marker provide further evidence of the phylogenetic position of Lunachloris. Minute vegetative cells of this newly recognized species are spherical or ellipsoid, with a single parietal chloroplast without a pyrenoid. Asexually, it reproduces by the formation of 2–6 autospores. Since the majority of recent attention has been paid to algae from the tropics or extreme habitats, the biodiversity of terrestrial microalgae in temperate regions is still notably unexplored and even a ‘common’ habitat like agricultural soil can contain new, as yet unknown species. Moreover, this study emphasizes the importance of culture collections of microorganisms even in the era of culture-independent biodiversity research, because they may harbour novel and undescribed organisms as well as preserving strains for future studies.     

Plastid‐encoded rbcL phylogeny suggests widespread distribution of Galdieria phlegrea (Cyanidiophyceae,Rhodophyta)

The rare microscopic red alga Galdieria phlegrea (Cyanidiohyceae, Rhodophyta) has been discovered in the extremely acid Tinto River in Spain and this occurrence is here related to previous knowledge about the distribution and ecology of this enigmatic alga. The taxonomic affiliation of the new isolate of G. phlegrea was revealed by reconstructing the phylogeny of plastid‐encoded rbcL. According to this phylogeny, the Tinto River alga is closely related to other G. phlegrea strains originating from extreme habitats in Czechia, Italy and Turkey, suggesting a wider distribution and higher ecological versatility than previously thought. The results suggest that G. phlegrea, and then possibly also other cyanidiophycean algae, are not as restricted to strongly acidic and hot microhabitats as previously believed, which, in turn, may indicate that they may commonly have been overlooked and possibly are much more widespread than is currently believed.     

Activation of the Endonuclease that Defines mRNA 3′ Ends Requires Incorporation into an 8-Subunit Core Cleavage and Polyadenylation Factor Complex

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Neuropathology of 16p13.11 deletion in epilepsy

16p13.11 genomic copy number variants are implicated in several neuropsychiatric disorders, such as schizophrenia, autism, mental retardation, ADHD and epilepsy. The mechanisms leading to the diverse clinical manifestations of deletions and duplications at this locus are unknown. Most studies favour NDE1 as the leading disease-causing candidate gene at 16p13.11. In epilepsy at least, the deletion does not appear to unmask recessive-acting mutations in NDE1, with haploinsufficiency and genetic modifiers being prime candidate disease mechanisms. NDE1 encodes a protein critical to cell positioning during cortical development. As a first step, it is important to determine whether 16p13.11 copy number change translates to detectable brain structural alteration. We undertook detailed neuropathology on surgically resected brain tissue of two patients with intractable mesial temporal lobe epilepsy (MTLE), who had the same heterozygous NDE1-containing 800 kb 16p13.11 deletion, using routine histological stains and immunohistochemical markers against a range of layer-specific, white matter, neural precursor and migratory cell proteins, and NDE1 itself. Surgical temporal lobectomy samples from a MTLE case known not to have a deletion in NDE1 and three non-epilepsy cases were included as disease controls. We found that apart from a 3 mm hamartia in the temporal cortex of one MTLE case with NDE1 deletion and known hippocampal sclerosis in the other case, cortical lamination and cytoarchitecture were normal, with no differences between cases with deletion and disease controls. How 16p13.11 copy changes lead to a variety of brain diseases remains unclear, but at least in epilepsy, it would not seem to be through structural abnormality or dyslamination as judged by microscopy or immunohistochemistry. The need to integrate additional data with genetic findings to determine their significance will become more pressing as genetic technologies generate increasingly rich datasets. Detailed examination of brain tissue, where available, will be an important part of this process in neurogenetic disease specifically.     

Regulation of proline and ethylene levels in rape seedlings for freezing tolerance

This study was aimed to investigate the possibility of regulating free proline content and ethylene production in the resistant to abiotic stress cv. ‘Hornet H’ and the tolerant to stress cv. ‘Sunday’ of winter rapeseed seedlings by pretreatment with exogenous L-proline and L-glutamine in non-acclimated and cold-acclimated seedlings in relation to freezing tolerance. The ratio of proline content in acclimated (at 4°C) versus non-acclimated (18°C) ‘Hornet H’ seedlings increased 2.12-fold and in ‘Sunday’ seedlings 1.95-fold. Exogenously applied, proline and glutamine produced a positive effect on free proline content in both cold-acclimated and non-acclimated seedlings. At a temperature of -1°C the proline content significantly increased in non-acclimated and especially in cold-acclimated seedlings. At an intensified freezing temperature (?3°C, ?5°C, ?7°C), the proline content decreased in comparison with that at ?1°C, but glutamine, especially proline, in cold-acclimated seedlings takes part in free proline level increase and in seedlings’ resistance to freezing. Ethylene production increased in cold-acclimated conditions and under the effect of exogenous proline and glutamine. In freezing conditions, ethylene production decreased, but in cold-acclimated seedlings and under pretreatment of proline and glutamine the ethylene synthesis was intensive. Thus, free proline content and ethylene production increase in cold-acclimated winter rapeseed seedlings and under pretreatment with glutamine and especially with proline. Free proline is involved in the response to cold stress, and its level may be an indicator of cold-hardening and freezing tolerance, but the role of ethylene in the regulation of cold tolerance remains not quite clear.     

No inbreeding depression for low temperature developmental acclimation across multiple Drosophila species

Populations are from time to time exposed to stressful temperatures. Their thermal resistance levels are determined by inherent and plastic mechanisms, which are both likely to be under selection in natural populations. Previous studies on Drosophila species have shown that inherent resistance is highly species specific, and differs among ecotypes (e.g., tropical and widespread species). Apart from being exposed to thermal stress many small and fragmented populations face genetic challenges due to, for example, inbreeding. Inbreeding has been shown to reduce inherent resistance levels toward stressful temperatures, but whether adaptation to thermal stress through plastic responses also is affected by inbreeding is so far not clear. In this study, we test inherent cold resistance and the ability to respond plastically to temperature changes through developmental cold acclimation in inbred and outbred lines of five tropical and five widespread Drosophila species. Our results confirm that tropical species have lower cold resistance compared to widespread species, and show that (1) inbreeding reduces inherent cold resistance in both tropical and widespread species, (2) inbreeding does not affect the ability to respond adaptively to temperature acclimation, and (3) tropical species with low basal resistance show stronger adaptive plastic responses to developmental acclimation compared to widespread species.     

Impact of chemical polymorphism of Thymus pulegioides on some associated plant species under natural and laboratory conditions

Abstract

Allelopathic potential of Thymus pulegioides L. chemical polymorphism was investigated under natural and laboratory conditions. A field analysis of 127 natural habitats hosting chemotypes of T. pulegioides with different ratios of phenolics, geraniol, and ɑ-terpinyl acetate was conducted. Effects of chemotypes, and their main compounds on seed germination and radicle growth of Trifolium pratense L. and Poa pratensis L. were conducted under laboratory conditions. Field analysis showed that Poa species were more plentiful in comparison with Trifolium species, independent of the chemotypical composition of T. pulegioides habitats. Laboratory tests with plant-acceptors showed a stronger inhibitory effect of essential oils on the germination and radicle growth of P. pratensis but in some instances germination was stimulated. Dissimilar effects were observed for the same allelochemical through air and water on the same plant-acceptor. Significantly, different effects of essential oils on radicle growth occurred in T. pratense and P. pratensis: with sensitivity to the phenolic chemotype via air and the ɑ-terpinyl acetate chemotype through water. This demonstrates that chemical polymorphism can expand communication opportunities of T. pulegioides with associated plant species. Combining investigations in natural habitats with laboratory experiments can help understand the effect of chemical polymorphism on plant-plant ecological interactions.     

Kainate induces various domain closures in AMPA and kainate receptors

Ionotropic glutamate receptors are key players in fast excitatory synaptic transmission within the central nervous system. These receptors have been divided into three subfamilies: the N-methyl-d-aspartic acid (NMDA), 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) and kainate receptors. Kainate has previously been crystallized with the ligand binding domain (LBD) of AMPA receptors (GluA2 and GluA4) and kainate receptors (GluK1 and GluK2). Here, we report the structures of the kainate receptor GluK3 LBD in complex with kainate and GluK1 LBD in complex with kainate in the absence of glycerol. Kainate introduces a conformational change in GluK3 LBD comparable to that of GluK2, but different from the conformational changes induced in GluA2 and GluK1. Compared to their domain closures in a glutamate bound state, GluA2 and GluK1 become more open and kainate induces a domain closure of 60% and 62%, respectively, relative to glutamate (100%). In GluK2 and GluK3 with kainate, the domain closure is 88% and 83%, respectively. In previously determined structures of GluK1 LBD in complex with kainate, glycerol is present in the binding site where it bridges interlobe residues and thus, might contribute to the large domain opening. However, the structure of GluK1 LBD with kainate in the absence of glycerol confirms that the observed domain closure is not an artifact of crystallization conditions. Comparison of the LBD structures with glutamate and kainate reveals that contacts are lost upon binding of kainate in the three kainate receptors, which is in contrast to the AMPA receptors where similar contacts are seen. It was revealed by patch clamp electrophysiology studies that kainate is a partial agonist at GluK1 with 36% efficacy compared to glutamate, which is in between the published efficacies of kainate at GluK2 and AMPA receptors. The ranking of efficacies seems to correlate with LBD domain closures.