Mitochondrial protein import: identification of processing peptidase and of PEP, a processing enhancing protein

Transport of nuclear-encoded precursor proteins into mitochondria includes proteolytic cleavage of amino-terminal targeting sequences in the mitochondrial matrix. We have isolated the processing activity from Neurospora crassa. The final preparation (enriched ca. 10,000-fold over cell extracts) consists of two proteins, the matrix processing peptidase (MPP, 57 kd) and a processing enhancing protein (PEP, 52 kd). The two components were isolated as monomers. PEP is about 15-fold more abundant in mitochondria than MPP. It is partly associated with the inner membrane, while MPP is soluble in the matrix. MPP alone has a low processing activity whereas PEP alone has no apparent activity. Upon recombining both, full processing activity is restored. Our data indicate that MPP contains the catalytic site and that PEP has an enhancing function. The mitochondrial processing enzyme appears to represent a new type of "signal peptidase," different from the bacterial leader peptidase and the signal peptidase of the endoplasmic reticulum.     

Evolution of chromosome number in grasshoppers (Orthoptera: Caelifera: Acrididae)

Organisms Diversity & Evolution - Orthoptera have some of the largest genomes of all insects. At the same time, the architecture of their genomes remains poorly understood. Comparative...     

Integrating field surveys and remote sensing data to study distribution, habitat use and conservation status of the herpetofauna of the Comoro Islands

We studied the non-marine reptile and amphibian species of the volcanic Comoro archipelago in the Western Indian Ocean, a poorly known island herpetofauna comprising numerous microendemic species of potentially high extinction risk and widespread, non-endemic and often invasive taxa. According to our data, the Comoro islands are inhabited by two amphibian species and at least 28 species of reptiles although ongoing genetic studies and unconfirmed historical records suggest an even higher species diversity. 14 of the 28 currently recognized species of terrestrial reptiles (50%) and the two amphibians are endemic to a single island or to the Comoro archipelago. The majority of species are most abundant at low elevation. However, a few endemic species, like the gekkonid lizards Paroedura sanctijohannis and Phelsuma nigristriata, are more common in or even confined to higher altitudes. We created habitat maps from remotely sensed data in combination with detailed species distribution maps produced using comprehensive data from field surveys between 2000 and 2010, literature, and historical locality records based on specimens in zoological collections. Using these data, we assessed the conservation status of the endemic terrestrial reptiles and amphibians according to the IUCN Red List criteria. Our results show that although little area of natural forest remains on the Comoros, many species are abundant in degraded forest or plantations. Competition and predation by invasive species appears to be the most important threat factor for the endemic herpetofauna, together with habitat degradation and destruction, which further favours invasive species. We propose the status Endangered for three species, Vulnerable for one species, Near Threatened for six species, Least Concern for four and Data Deficient for two species. The endemic subspecies Oplurus cuvieri comorensis is proposed for the status Critically Endangered. Based on the results of this study, seven areas of importance for reptile and amphibian conservation on the Comoros are identified. This study shows how remote sensing data can contribute to increasing accuracy and objectiveness of conservation assessments.     

Analysis of geographic centrality and genetic diversity in the declining grasshopper species Bryodemella tuberculata (Orthoptera: Oedipodinae)

Human-induced ecological and climatic changes have led to the decline and even local extinction of many formerly widely distributed temperate and cold-adapted species. Determining the exact causes of this decline remains difficult. Bryodemella tuberculata was a widely distributed orthopteran species before the mid-19th century. Since then, many European populations have suffered drastic declines and are now considered extinct or critically endangered. We used ecological niche modelling based on a large dataset of extant and extinct occurrence data to investigate whether poor climatic suitability in the periphery of its global range was a possible cause of the local extinction of the European populations of B. tuberculata. We also used population genetics based on the COI marker to estimate and compare the genetic diversity of extant populations. We found that Europe still provides highly suitable habitats close to the climatic optimum, contradicting the assumption of climate change as major driver of this decline. Instead, changes in land-cover and other anthropogenic modifications of the habitats at the local scale seem to be the major reasons for local extinctions. Genetic analysis suggests Central Asia as center of diversity with a stable population size, whereas the effective sizes of the remaining European populations are decreasing. We found European genetic lineages nested within Central Asian lineages, suggesting a Central Asian source distribution area. Our results suggest that the declining European populations represent relics of a formerly wider distribution, which was fragmented by changes in land-use. These relics are now threatened by limited connectivity and small effective population sizes. Specific conservation actions, such as the restoration of former or potential new habitats, and translocation of individuals from extant populations to these restored sites may help slow, stall, or even revert the extinction process.

     

Ecological niche modelling and nDNA sequencing support a new, morphologically cryptic beetle species unveiled by DNA barcoding

Background

DNA sequencing techniques used to estimate biodiversity, such as DNA barcoding, may reveal cryptic species. However, disagreements between barcoding and morphological data have already led to controversy. Species delimitation should therefore not be based on mtDNA alone. Here, we explore the use of nDNA and bioclimatic modelling in a new species of aquatic beetle revealed by mtDNA sequence data.

Methodology/Principal Findings

The aquatic beetle fauna of Australia is characterised by high degrees of endemism, including local radiations such as the genus Antiporus. Antiporus femoralis was previously considered to exist in two disjunct, but morphologically indistinguishable populations in south-western and south-eastern Australia. We constructed a phylogeny of Antiporus and detected a deep split between these populations. Diagnostic characters from the highly variable nuclear protein encoding arginine kinase gene confirmed the presence of two isolated populations. We then used ecological niche modelling to examine the climatic niche characteristics of the two populations. All results support the status of the two populations as distinct species. We describe the south-western species as Antiporus occidentalis sp.n.

Conclusion/Significance

In addition to nDNA sequence data and extended use of mitochondrial sequences, ecological niche modelling has great potential for delineating morphologically cryptic species.     

Antihypertensive and cardioprotective effects of different monotherapies and combination therapies in young spontaneously hypertensive rats – A pilot study

Spontaneously hypertensive rats (SHR) are an established animal model for antihypertensive treatment. The aim of this pilot study was a systematic search for two lines of antihypertensive treatment – a monotherapy and a combination of two drugs – to be applied in a future study on old SHR. Originally, representatives of three drug classes recommended for antihypertensive therapy in humans should be applied, namely captopril (CAP) as an antagonist of the renin-angiotensin-aldosterone system, nifedipine (NIF) as calcium channel blocker and propranolol (PROP) as β-adrenergic blocker. As we observed that PROP had been poorly ingested, all groups with PROP therapy were excluded from the study. CAP (60 mg kg⁻¹ d^-1), NIF (10 mg kg⁻¹ d^-1) or both were administered orally to seven-week-old SHR over 3 weeks. A further group of SHR received no treatment (SHR/CTRL). Age-matched normotensive Wistar-Kyoto rats served as normotensive controls. We examined the effect of the antihypertensive therapies on systolic blood pressure, heart weight and on histological and biochemical markers of cardiac hypertrophy and fibrosis.CAP proved to be the most effective treatment reducing blood pressure and relative heart weight significantly compared to SHR/CTRL without reaching normotensive values. Beginning cardiac fibrosis observed in SHR/CTRL was completely abrogated with CAP treatment. Similar effects were achieved with a combination of CAP and NIF. CAP as monotherapy and CAP + NIF as combination therapy were chosen for the forthcoming study on old SHR.Keyword: Young SHR, Antihypertensive therapy, Blood pressure monitoring, Cardiac hypertrophy, Cardiac fibrosis     

New insights into the systematics and molecular phylogeny of the Malagasy snake genus Liopholidophis suggest at least one rapid reversal of extreme sexual dimorphism in tail length

The pseudoxyrhophiine snake genus Liopholidophis Mocquard, 1904 (family Lamprophiidae) is endemic to Madagascar and according to its present definition comprises six medium-sized, terrestrial and diurnal snake species, most of which are characterised by an unusual and extreme sexual dimorphism in tail length. We performed molecular phylogenetic analyses using nucleotide sequences of three mitochondrial genes (16S rRNA, cytochrome b and cytochrome oxidase I) and one nuclear gene (c-mos) for all described and two additional species newly described herein. The two new species are very small sized (total length: 234–312.5 mm), have comparatively short tails and a reduced number of dorsal scale rows (15 at midbody), the lowest value among all non-scolecophidian snakes of Madagascar. Both species are secretive or rare, and they have a reddish belly in life that fades in preservative. In terms of colouration and morphology, they are most similar to each other and furthermore to Liopholidophis rhadinaea. Together with this species and L. dimorphus, they form a well-supported clade. Liopholidophis baderi sp. nov. from central eastern Madagascar is characterised by 149–158 ventrals and 71–77 subcaudals, whereas the similar L. oligolepis sp. nov. from the northeast has even fewer ventrals (137) and subcaudals (54). The phylogenetic tree suggests that the tail length dimorphism in the genus Liopholidophis has evolved in a complex pattern including at least one reversal. The phylogenetic position of the two new dwarf species indicates that both the absence of extreme sexual dimorphism in tail length and their body size reduction are derived and probably correlated features. Also the close phylogenetic relationships between the long-tailed L. sexlineatus and the similar but relatively short-tailed L. varius demonstrate that dimorphism in tail length can be strongly mitigated in short evolutionary time periods.     

Pleistocene climate change promoted rapid diversification of aquatic invertebrates in Southeast Australia

ABSTRACT: BACKGROUND: The Pleistocene Ice Ages were the most recent geohistorical event of major global impact, but their consequences for most parts of the Southern hemisphere remain poorly known. We investigate a radiation of ten species of Sternopriscus, the most species-rich genus of epigean Australian diving beetles. These species are distinct based on genital morphology but cannot be distinguished readily by mtDNA and nDNA because of genotype sharing caused by incomplete lineage sorting. Their genetic similarity suggests a Pleistocene origin. RESULTS: We use a dataset of 3858 bp of mitochondrial and nuclear DNA to reconstruct a phylogeny of Sternopriscus using gene and species trees. Diversification analyses support the finding of a recent rapid speciation event with estimated speciation rates of up to 2.40 species per MY, which is considerably higher than the proposed average rate of 0.16 species per MY for insects. Additionally, we use ecological niche modeling and analyze data on habitat preferences to test for niche divergence between species of the recent Sternopriscus radiation. These analyses show that the species can be characterized by a set of ecological variables referring to habitat, climate and altitude. CONCLUSIONS: Our results suggest that the repeated isolation of populations in glacial refugia might have led to divergent ecological adaptations and the fixation of morphological traits supporting reproductive isolation and therefore may have promoted speciation. The recent Sternopriscus radiation fulfills many characteristics of a species flock and would be the first described example of an aquatic insect species flock. We argue that the species of this group may represent a stage in speciation past the species flock condition because of their mostly broad and often non-overlapping ranges and preferences for different habitat types.     

DNA barcoding of crickets,katydids and grasshoppers (Orthoptera) from Central Europe with focus on Austria,Germany and Switzerland

We present a DNA barcoding study on the insect order Orthoptera that was generated in collaboration between four barcoding projects in three countries, viz. Barcoding Fauna Bavarica (Germany), German Barcode of Life, Austrian Barcode of Life and Swiss Barcode of Life. Our data set includes 748 COI sequences from 127 of the 162 taxa (78.4%) recorded in the three countries involved. Ninety‐three of these 122 species (76.2%, including all Ensifera) can be reliably identified using DNA barcodes. The remaining 26 caeliferan species (families Acrididae and Tetrigidae) form ten clusters that share barcodes among up to five species, in three cases even across different genera, and in six cases even sharing individual barcodes. We discuss incomplete lineage sorting and hybridization as most likely causes of this phenomenon, as the species concerned are phylogenetically young and hybridization has been previously observed. We also highlight the problem of nuclear mitochondrial pseudogenes (numts), a known problem in the barcoding of orthopteran species, and the possibility of Wolbachia infections. Finally, we discuss the possible taxonomic implications of our barcoding results and point out future research directions.