The phylogenetic affinities of the chaetognaths: a molecular analysis

The chaetognaths, or arrowworms, constitute a small and enigmatic phylum of marine invertebrates whose phylogenetic affinities have long been uncertain. A popular hypothesis is that the chaetognaths are the sister group of the major deuterostome phyla: chordates, hemichordates, and echinoderms. Here we attempt to determine the affinities of the chaetognaths by using molecular sequence data. We describe the isolation and nucleotide sequence determination of 18S ribosomal DNA from one species of chaetognath and one acanthocephalan. Extensive phylogenetic analyses employing a suite of phylogenetic reconstruction methods (maximum parsimony, maximum likelihood, evolutionary parsimony, and two distance methods) suggest that the hypothesized relationship between chaetognaths and the deuterostomes is incorrect. In contrast, we propose that the lineage leading to the chaetognaths arose prior to the advent of the coelomate metazoa.      

Molecular evolution of P transposable elements in the genus Drosophila. I. The saltans and willistoni species groups

A phylogenetic survey using the polymerase chain reaction (PCR) has identified four major P element subfamilies in the saltans and willistoni species groups of Drosophila. One subfamily, containing about half of the sequences studied, consists of elements that are very similar to the canonical (and active) P element from D. melanogaster. Within this subfamily, nucleotide sequence differentiation among different copies from the same species and among elements from different species is relatively low. This observation suggests that the canonical elements are relatively recent additions to the genome or, less likely, are evolving slowly relative to the other subfamilies. Elements belonging to the three noncanonical lineages are distinct from the canonical elements and from one another. Furthermore, there is considerably more sequence variation, on the average, within the noncanonical subfamilies compared to the canonical elements. Horizontal transfer and the coexistence of multiple, independently evolving element subfamilies in the same genome may explain the distribution of P elements in the saltans and willistoni species groups. Such explanations are not mutually exclusive, and each may be involved to varying degrees in the maintenance of P elements in natural populations of Drosophila.      

Discovery of protein-protein binding disruptors using multi-component condensations small molecules

A series of small molecule compounds interfering with the binding process of VEGF and NRP1 has been identified and further optimized. Full synthetic details as well as SAR are reported which demonstrate that expeditious MCC-based syntheses may lead to valuable molecules addressing challenging targets such as protein-protein interactions. Preliminary functional assay data confirm that these compounds may be further developed toward drug candidates.     

What Image Properties Regulate Eye Growth?

The growth of the eye, unlike other parts of the body, is not ballistic. It is guided by visual feedback with the eventual aim being optimal focus of the retinal image or emmetropization . It has been shown in animal models that interference with the quality of the retinal image leads to a disruption to the normal growth pattern, resulting in the development of refractive errors and defocused retinal images . While it is clear that retinal images rich in pattern information are needed to control eye growth, it is unclear what particular aspect of image structure is relevant. Retinal images comprise a range of spatial frequencies at different absolute and relative contrasts and in different degrees of spatial alignment. Here we show, by using synthetic images, that it is not the local edge structure produced by relative spatial frequency alignments within an image but rather the spatial frequency composition per se that is used to regulate the growth of the eye. Furthermore, it is the absolute energy at high spatial frequencies regardless of the spectral slope that is most effective. Neither result would be expected from currently accepted ideas of how human observers judge the degree of image "blur" in a scene where both phase alignments and the relative energy distribution across spatial frequency (i.e., spectral slope) are important.     

Longitudinal proxy measurements in multiple sclerosis: patient-proxy agreement on the impact of MS on daily life over a period of two years

Background  

The use of self-report measurements in clinical settings is increasing. However, in patients with limitations that interfere with reliable self-assessment such as cognitive impairment or mood disturbances, as may be the case in multiple sclerosis (MS), data collection might be problematic. In these situations, information obtained from proxy respondents (e.g. partners) may replace self-ratings. The aim of this study was to examine the value of proxy ratings at separate points in time and to assess patient-proxy agreement on possible changes in disease impact of MS.     

Towards a reporter system to identify regulators of cross-talk between salicylate and jasmonate signaling pathways in Arabidopsis

The plant signaling hormones salicylic acid (SA) and jasmonic acid (JA) are regulators of inducible defenses that are activated upon pathogen or insect attack. Cross-talk between SA- and JA-dependent signaling pathways allows a plant to finely tune its response to the attacker encountered. In Arabidopsis, pharmacological experiments revealed that SA exerts a strong antagonistic effect on JA-responsive genes, such as PDF1.2, indicating that the SA pathway can be prioritized over the JA pathway. SA-mediated suppression of the JA-responsive PDF1.2 promoter was exploited for setting up a genetic screen aiming at the isolation of signal transduction mutants that are impaired in this cross-talk mechanism. The PDF1.2 promoter was fused to the herbicide resistance gene BAR to allow for life/death screening of a population of mutagenized transgenic plants. Non-mutant plants should survive herbicide treatment when methyl jasmonate (MeJA) is applied, but suppression of the JA response by SA should be lethal in combination with the herbicide. Conversely, crucial SA/JA cross-talk mutants should survive the combination treatment. SA effectively suppressed the expression of the PDF1.2::BAR transgene. However, suppression of the BAR gene did not result in suppression of herbicide resistance. Hence, a screening method based on quantitative differences in the expression of a reporter gene may be better suited to identify SA/JA cross-talk mutants. Here, we demonstrate that the PDF1.2::GUS reporter will be excellently suited in this respect.Key words: plant defense, salicylic acid, jasmonic acid, cross-talk, mutant screen, Arabidopsis