Chlorophyll fluorescence emission as a reporter on cold tolerance in Arabidopsis thaliana accessions

Non-invasive, high-throughput screening methods are valuable tools in breeding for abiotic stress tolerance in plants. Optical signals such as chlorophyll fluorescence emission can be instrumental in developing new screening techniques. In order to examine the potential of chlorophyll fluorescence to reveal plant tolerance to low temperatures, we used a collection of nine Arabidopsis thaliana accessions and compared their fluorescence features with cold tolerance quantified by the well established electrolyte leakage method on detached leaves. We found that, during progressive cooling, the minimal chlorophyll fluorescence emission rose strongly and that this rise was highly dependent on the cold tolerance of the accessions. Maximum quantum yield of PSII photochemistry and steady state fluorescence normalized to minimal fluorescence were also highly correlated to the cold tolerance measured by the electrolyte leakage method. In order to further increase the capacity of the fluorescence detection to reveal the low temperature tolerance, we applied combinatorial imaging that employs plant classification based on multiple fluorescence features. We found that this method, by including the resolving power of several fluorescence features, can be well employed to detect cold tolerance already at mild sub-zero temperatures. Therefore, there is no need to freeze the screened plants to the largely damaging temperatures of around −15°C. This, together with the method''s easy applicability, represents a major advantage of the fluorescence technique over the conventional electrolyte leakage method.Key words: chlorophyll fluorescence, cold acclimation, electrolyte leakage, high-throughput screening, natural accessions     

The phylogeny of monkey beetles based on mitochondrial and ribosomal RNA genes (Coleoptera: Scarabaeidae: Hopliini)

Monkey beetles (Hopliini) are a large clade of flower and leaf feeding species within the Scarabaeidae (chafers) with greatest diversity in southern Africa. Their internal relationships and sister group affinities have not been studied with DNA methods. We used partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 158 species, representing most recognized subfamilies of Scarabaeidae, including 46 species of Hopliini. Combined analyses using maximum likelihood and Bayesian inference under the two preferred alignment parameters recovered the Hopliini as monophyletic. Hopliines were inserted at the base of a clade of Cetoniinae+Rutelinae+Dynastinae, being either recovered as their immediate sister group, or as part of an expanded set of basal branches that also includes the tribe Macrodactylini which has been classified as part of the Melolonthinae (may chafers). At the level of subtribes, we found Hopliina paraphyletic with respect to Pachycnemina which also includes the monophyletic clade of Heterochelina and Gymnolomina. Trait mapping under parsimony on the preferred tree resulted in inferences of three independent origins of sexual dimorphism, which coincided with shifts to 'flower-embedding' pollination. In contrast, night active taxa, which are general phyllophages as other pleurostict chafers, never show clear sexual dimorphism. South African lineages include several deep-branching lineages. The exceptional morphological and phylogenetic diversity of the South African fauna may therefore be due to their antiquity, in addition to sexual selection in the day-active lineages. Phylogenetic studies of the endemic South African plant radiations have demonstrated the repeated evolutionary shift to beetle pollination, but it remains to be investigated if this is driven by the hopliine pollinators present in the bioregion or by a propensity of the local plant lineages favoring this pollination syndrome.     

Tularemia in Alaska, 1938 - 2010

Background

A major challenge in sheep farming during the grazing season along the coast of south-western Norway is tick-borne fever (TBF) caused by the bacteria Anaplasma phagocytophilum that is transmitted by the tick Ixodes ricinus.

Methods

A study was carried out in 2007 and 2008 to examine the prevalence of A. phagocytophilum infection and effect on weaning weight in lambs. The study included 1208 lambs from farms in Sunndal Ram Circle in Møre and Romsdal County in Mid-Norway, where ticks are frequently observed. All lambs were blood sampled and serum was analyzed by an indirect fluorescent antibody assay (IFA) to determine an antibody status (positive or negative) to A. phagocytophilum infection. Weight and weight gain and possible effect of infection were analyzed using ANOVA and the MIXED procedure in SAS.

Results

The overall prevalence of infection with A. phagocytophilum was 55%. A lower weaning weight of 3% (1.34 kg, p < 0.01) was estimated in lambs seropositive to an A. phagocytophilum infection compared to seronegative lambs at an average age of 137 days.

Conclusions

The results show that A. phagocytophilum infection has an effect on lamb weight gain. The study also support previous findings that A. phagocytophilum infection is widespread in areas where ticks are prevalent, even in flocks treated prophylactic with acaricides.     

Evolutionary dynamics of a satellite DNA in the tiger beetle species pair Cicindela campestris and C. maroccana.

Satellite repeat elements are an abundant component of eukaryotic genomes, but not enough is known about their evolutionary dynamics and their involvement in karyotype and species differentiation. We report the nucleotide sequence, chromosomal localization, and evolutionary dynamics of a repetitive DNA element of the tiger beetle species pair Cicindela maroccana and Cicindela campestris. The element was detected after restriction digest of C. maroccana total genomic DNA with EcoRI as a single band and its multimers on agarose gels. Cloning and sequencing of several isolates revealed a consensus sequence of 383 bp with no internal repeat structure and no detectable similarity to any entry in GenBank. Hybridization of the satellite unit to C. maroccana mitotic and meiotic chromosomes revealed the presence of this repetitive DNA in the centromeres of all chromosomes except the Y chromosome, which exhibited only a very weak signal in its short arm. PCR-based tests for this satellite in related species revealed its presence in the sister species C. campestris, but not in other closely related species. Phylogenetic analysis of PCR products revealed well-supported clades that generally separate copies from each species. Because both species exhibit the multiple X chromosome karyotypic system common to Cicindela, but differ in their X chromosome numbers (four in C. maroccana vs. three in C. campestris), structural differences could also be investigated with regard to the position of satellites in a newly arisen X chromosome. We find the satellite in a centromeric position in all X chromosomes of C. maroccana, suggesting that the origin of the additional X chromosome involves multiple karyotypic rearrangements.     

On the constitution and phylogeny of Staphyliniformia (Insecta: Coleoptera)

The Staphyliniformia is one of the most diverse lineages of Coleoptera, with representatives occupying every conceivable non-marine niche. Phylogenetic relationships among its varied families and lower taxa have defied resolution. The problem has been further complicated by the recent suggestion that another major coleopteran series, Scarabaeiformia, is derived from within it. Here we present the first phylogenetic analyses, based on 18S rDNA sequences and morphological data, to explicitly examine this possibility. Thorough evaluation of alternative alignments and tree construction methods support the contention that Scarabaeiformia is derived from within Staphyliniformia. Though the analyses yielded strong support for few family level groupings within the expanded Staphyliniformia, they conclusively support a close relationship between Hydraenidae and Ptiliidae, which has often been debated. The primary factor hindering additional resolution appears to be the inconsistent rate of divergence in 18S among these taxa.     

Towards writing the encyclopedia of life: an introduction to DNA barcoding

An international consortium of major natural history museums, herbaria and other organizations has launched an ambitious project, the 'Barcode of Life Initiative', to promote a process enabling the rapid and inexpensive identification of the estimated 10 million species on Earth. DNA barcoding is a diagnostic technique in which short DNA sequence(s) can be used for species identification. The first international scientific conference on Barcoding of Life was held at the Natural History Museum in London in February 2005, and here we review the scientific challenges discussed during this conference and in previous publications. Although still controversial, the scientific benefits of DNA barcoding include: (i) enabling species identification, including any life stage or fragment, (ii) facilitating species discoveries based on cluster analyses of gene sequences (e.g. cox1 = CO1, in animals), (iii) promoting development of handheld DNA sequencing technology that can be applied in the field for biodiversity inventories and (iv) providing insight into the diversity of life.     

Cardiac troponin C-L29Q, related to hypertrophic cardiomyopathy, hinders the transduction of the protein kinase A dependent phosphorylation signal from cardiac troponin I to C

We investigated structural and functional aspects of the first mutation in TNNC1, coding for the calcium-binding subunit (cTnC) of cardiac troponin, which was detected in a patient with hypertrophic cardiomyopathy [ Hoffmann B, Schmidt-Traub H, Perrot A, Osterziel KJ & Gessner R (2001) Hum Mut17, 524]. This mutation leads to a leucine-glutamine exchange at position 29 in the nonfunctional calcium-binding site of cTnC. Interestingly, the mutation is located in a putative interaction site for the nonphosphorylated N-terminal arm of cardiac troponin I (cTnI) [ Finley NL, Abbott MB, Abusamhadneh E, Gaponenko V, Dong W, Seabrook G, Howarth JW, Rana M, Solaro RJ, Cheung HC et al. (1999) EJB Lett453, 107-112]. According to peptide array experiments, the nonphosphorylated cTnI arm interacts with cTnC around L29. This interaction is almost abolished by L29Q, as observed upon protein kinase A-dependent phosphorylation of cTnI at serine 22 and serine 23 in wild-type troponin. With CD spectroscopy, minor changes are observed in the backbone of Ca2+-free and Ca2+-saturated cTnC upon the L29Q replacement. A small, but significant, reduction in calcium sensitivity was detected upon measuring the Ca2+-dependent actomyosin subfragment 1 (actoS1)-ATPase activity and the sliding velocity of thin filaments. The maximum actoS1-ATPase activity, but not the maximum sliding velocity, was significantly enhanced. In addition, we performed our investigations at different levels of protein kinase A-dependent phosphorylation of cTnI. The in vitro assays mainly showed that the Ca2+ sensitivity of the actoS1-ATPase activity, and the mean sliding velocity of thin filaments, were no longer affected by protein kinase A-dependent phosphorylation of cTnI owing to the L29Q exchange in cTnC. The findings imply a hindered transduction of the phosphorylation signal from cTnI to cTnC.     

Involvement of Smad signaling in sphingosine 1-phosphate-mediated biological responses of keratinocytes

The lysophospholipid sphingosine 1-phosphate and the cytokine-transforming growth factor beta are both released from degranulating platelets at wound sites, suggesting a broad spectrum of effects involved in wound healing. Interestingly, both of these molecules have been previously shown to induce chemotaxis but to strongly inhibit the growth of keratinocytes, while stimulating the proliferation of fibroblasts. In contrast to sphingosine 1-phosphate, the signaling cascade of the growth factor has been extensively examined. Specifically, Smad3 has been shown to be an essential mediator of transforming growth factor beta-dependent chemotaxis of keratinocytes and mediates, in part, its growth-inhibitory effect. Here we show that sphingosine 1-phosphate, independently of transforming growth factor beta secretion, induces a rapid phosphorylation of Smad3 on its C-terminal serine motif and induces its partnering with Smad4 and the translocation of the complex into the nucleus. Moreover, sphingosine 1-phosphate fails to induce chemotaxis or inhibit the growth of Smad3-deficient keratinocytes, suggesting that Smad3 plays an unexpected functional role as a new target in sphingosine 1-phosphate signaling. Both sphingosine 1-phosphate receptors and the transforming growth factor beta-type I receptor serine/threonine kinase are essential for activation of Smad3 by this lysophospholipid and the dependent biological responses, indicating a novel cross-talk between serine/threonine kinase receptors and G-protein coupled receptors.