Replication Orientation Affects the Rate and Direction of Bacterial Gene Evolution

In many bacterial genomes, the leading and lagging strands have different skews in base composition; for example, an excess of guanosine compared to cytosine on the leading strand. We find that Chlamydia genes that have switched their orientation relative to the direction of replication, for example by inversion, acquire the skew of their new ``host' strand. In contrast to most evolutionary processes, which have unpredictable effects on the sequence of a gene, replication-related skews reflect a directional evolutionary force that causes predictable changes in the base composition of switched genes, resulting in increased DNA and amino acid sequence divergence. Received: 27 April 2000 / Accepted: 1 August 2000     

Common Properties of Fusion Peptides from Diverse Systems

Although membrane fusion occurs ubiquitously and continuously in alleukaroytic cells, little is known about the mechanism that governs lipidbilayer fusion associated with any intracellular fusion reactions. Recentstudies of the fusion of enveloped viruses with host cell membranes havehelped to define the fusion process. The identification and characterizationof key proteins involved in fusion reactions have mainly driven recent advancesin our understanding of membrane fusion. The most important denominator amongthe fusion proteins is the fusion peptide. In this review, work done in thelast few years on the molecular mechanism of viral membrane fusion will behighlighted, focusing in particular on the role of the fusion peptide and themodification of the lipid bilayer structure. Much of what is known regardingthe molecular mechanism of viral membrane fusion has been gained using liposomesas model systems in which the molecular components of the membrane and the environmentare strictly controlled. Many amphilphilic peptides have a high affinity forlipid bilayers, but only a few sequences are able to induce membrane fusion. Thepresence of -helical structure in at least part of the fusion peptideis strongly correlated with activity whereas, -structure tends to beless prevalent, associated with non-native experimental conditions, and morerelated to vesicle aggregation than fusion. The specific angle of insertionof the peptides into the membrane plane is also found to be an importantcharacteristic for the fusion process. A shallow penetration, extending onlyto the central aliphatic core region, is likely responsible for the destabilization ofthe lipids required for coalescence of the apposing membranes and fusion.     

Potential carbon gain of shingle leaves in juveniles of the vine Monstera tenuis (Araceae) in Costa Rica

The amount of light intercepted by vertically oriented, shingle leaves of juvenile Monstera tenuis vines growing in forest understory was compared to the amount of light the leaves would intercept if they were horizontal. Light levels were monitored using quantum sensors and hemispherical photography. Shingle leaves absorb less light than they would if the leaves were horizontal at the same positions, and the difference increases with height in the forest. Modeling based on measured photosynthetic light responses and light interception suggests that at 1 m height, 75% more carbon could be gained if leaves were horizontal instead of vertical. Because the vertical leaf orientation reduces light interception, other selective factors are likely of greater importance in favoring the evolution of the shingle-leaved growth form.     

Multiple Molecular Mechanisms Underlying Subdiagnostic Variants of Marfan Syndrome

Mutations in the FBN1 gene, which encodes fibrillin-1, cause Marfan syndrome (MFS) and have been associated with a wide range of milder, overlap phenotypes. The factors that modulate phenotypic severity, both between and within families, remain to be determined. This study examines the relationship between the FBN1 genotype and phenotype in families with extremely mild phenotypes and in those that show striking clinical variation among apparently affected individuals. In one family, clinically similar but etiologically distinct disorders are segregating independently. In another, somatic mosaicism for a mutant FBN1 allele is associated with subdiagnostic manifestations, whereas germ-line transmission of the identical mutation causes severe and rapidly progressive disease. A third family cosegregates mild mitral valve prolapse syndrome with a mutation in FBN1 that can be functionally distinguished from those associated with the classic MFS phenotype. These data have immediate relevance for the diagnostic and prognostic counseling of patients and their family members.     

Base Composition Skews, Replication Orientation, and Gene Orientation in 12 Prokaryote Genomes

Variation in GC content, GC skew and AT skew along genomic regions was examined at third codon positions in completely sequenced prokaryotes. Eight out of nine eubacteria studied show GC and AT skews that change sign at the origin of replication. The leading strand in DNA replication is G-T rich at codon position 3 in six eubacteria, but C-T rich in two Mycoplasma species. In M. genitalium the AT and GC skews are symmetrical around the origin and terminus of replication, whereas its GC content variation has been shown to have a centre of symmetry elsewhere in the genome. Borrelia burgdorferi and Treponema pallidum show extraordinary extents of base composition skew correlated with direction of DNA replication. Base composition skews measured at third codon positions probably reflect mutational biases, whereas those measured over all bases in a sequence (or at codon positions 1 and 2) can be strongly affected by protein considerations due to the tendency in some bacteria for genes to be transcribed in the same direction that they are replicated. Consequently in some species the direction of skew for total genomic DNA is opposite to that for codon position 3. Received: 2 February 1998 / Accepted: 15 June 1998     

The diversity of lectin-detectable sugar residues on root hair tips of selected legumes correlates with the diversity of their host ranges for rhizobia

Summary Glomerulocyte cellulosic bundles ofPolyzoa vesiculiphora were investigated by microdiffraction and high-resolution electron microscopy. In each bundle, hundreds of cellulose microfibrils, having a rectangular cross-sectional shape, are packed regularly with their 0.6 nm lattice planes parallel to each other. Lattice images reveal that the 0.6 nm plane is parallel to the longer edge of the cross section which is similar to the lattice organization of cellulose with a squarish cross section inValonia spp. More interestingly, all the microfibrils in a bundle have the same directionality of crystallographic c-axis, which suggests that the biosynthesis of the microfibrils within particular bundle occurs unidirectionally.     

Sources of information controlling motor patterns in arthropod local search orientation

Search orientation is controlled by information that is stored genetically, idiothetically or through learning and that is gained from internal and external sensory systems. Sources of variation in motor patterns could derive from any of the types of information, or could originate during the execution of the instructions derived from orientation information. Local search after resource utilization in the flies Musca demestica and Drosophila melanogaster can be addressed as an initial increase in turning rate and decrease in locomotory rate, followed by a transition in both measures to a lower turning rate and a higher locomotory rate characteristic of ranging. The search tactic of flies promotes accrual of discrete resources in a patch. A forward-moving tendency, combined with a “noisy” looping motor pattern, enhances resource-finding in both linear and non-linear resource patterns. The period before a fly leaves a patch—its giving-up-time—is a function of current resource density and the slope of the transition from local search to ranging: once a fly switches to the relatively straight path characteristic of ranging, the chances of it leaving the patch depends on whether or not another resource is encountered. Duration of local search is dependent on the genotype of an individual, level of starvation or satiation, resource quality (sucrose concentration) and quantity (patch size) and presence of resource-specific sensory information.     

Gender, sex role orientation, and dream recall frequency.

[Correction Notice: An erratum for this article was reported in Vol 20(3) of Dreaming (see record 2010-17362-006). In the article, a third author was not listed in the byline and some acknowledgment information was also missing: Third Co-Author: Anja S. G?ritz, University of Würzburg, Würzburg, Germany Additional Acknowledgment: We thank the operators of the sites www.panopia.de, www.yougov.de, and www.studivz.net for providing participants. This work was in part supported by DFG grant GO 1107/4-1 to G?ritz. The online version of the article has been corrected.] Recently, a large meta-analysis showed that women tend to recall their dreams more often than men. Despite this robust finding, studies focused on explaining the gender difference in dream recall frequency are scarce. The present findings of an online survey indicate that sex role orientation—expressivity/femininity—was related to dream recall frequency but did not fully explain the gender difference in dream recall frequency. Future studies should investigate other variables—in addition to sex role orientation—like verbal memory, recall of emotional experiences, and/or frequency of talking about emotional matters that might play a role in explaining the gender difference in dream recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

“Gender, sex role orientation and dream recall frequency”: Correction.

Reports an error in "Gender, sex role orientation, and dream recall frequency" by Michael Schredl and Olaf Lahl (Dreaming, 2010[Mar], Vol 20[1], 19-24). In the article, a third author was not listed in the byline and some acknowledgment information was also missing: Third Co-Author: Anja S. G?ritz, University of Würzburg, Würzburg, Germany. The name appears in this record. Additional Acknowledgment: We thank the operators of the sites www.panopia.de, www.yougov.de, and www.studivz.net for providing participants. This work was in part supported by DFG grant GO 1107/4-1 to G?ritz. The online version of the article has been corrected. (The following abstract of the original article appeared in record 2010-05656-002.) Recently, a large meta-analysis showed that women tend to recall their dreams more often than men. Despite this robust finding, studies focused on explaining the gender difference in dream recall frequency are scarce. The present findings of an online survey indicate that sex role orientation—expressivity/femininity—was related to dream recall frequency but did not fully explain the gender difference in dream recall frequency. Future studies should investigate other variables—in addition to sex role orientation—like verbal memory, recall of emotional experiences, and/or frequency of talking about emotional matters that might play a role in explaining the gender difference in dream recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)