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1.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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2.
A wide-ranging examination of plastid (pt)DNA sequence homologies within
higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion
with methylation-sensitive restriction enzymes and Southern analysis was
used to distinguish plastid and nuclear DNA in order to assess the extent
of variability of promiscuous sequences within and between plant species.
Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum
(tobacco), and Chenopodium quinoa, showed homogenity of these sequences,
while intraspecific sequence variation was observed among different
cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum
aestivum (wheat). Hypervariability of plastid sequence homologies was
identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta
vulgaris (beet), in which individual plants were shown to possess a unique
spectrum of nuclear sequences with ptDNA homology. This hypervariability
apparently extended to somatic variation in B. vulgaris. No sequences with
ptDNA homology were identified by this method in the nuclear genome of
Arabidopsis thaliana.
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3.
Marc A. Schlüter Catherine S. Pfarr Jay Pieczynski Eileen L. Whiteman Toby W. Hurd Shuling Fan Chia-Jen Liu Ben Margolis 《Molecular biology of the cell》2009,20(22):4652-4663
Although lumen generation has been extensively studied through so-called cyst-formation assays in Madin-Darby canine kidney (MDCK) cells, an underlying mechanism that leads to the initial appearance of a solitary lumen remains elusive. Lumen formation is thought to take place at early stages in aggregates containing only a few cells. Evolutionarily conserved polarity protein complexes, namely the Crumbs, Par, and Scribble complexes, establish apicobasal polarity in epithelial cells, and interference with their function impairs the regulated formation of solitary epithelial lumina. Here, we demonstrate that MDCK cells form solitary lumina during their first cell division. Before mitosis, Crumbs3a becomes internalized and concentrated in Rab11-positive recycling endosomes. These compartments become partitioned in both daughter cells and are delivered to the site of cytokinesis, thus forming the first apical membrane, which will eventually form a lumen. Endosome trafficking in this context appears to depend on the mitotic spindle apparatus and midzone microtubules. Furthermore, we show that this early lumen formation is regulated by the apical polarity complexes because Crumbs3 assists in the recruitment of aPKC to the forming apical membrane and interference with their function can lead to the formation of a no-lumen or multiple-lumen phenotype at the two-cell stage. 相似文献
4.
Straight SW Pieczynski JN Whiteman EL Liu CJ Margolis B 《The Journal of biological chemistry》2006,281(49):37738-37747
Mammalian Lin-7 forms a complex with several proteins, including PALS1, that have a role in polarity determination in epithelial cells. In this study we have found that loss of Lin-7 protein from the polarized epithelial cell line Madin-Darby canine kidney II by small hairpin RNA results in defects in tight junction formation as indicated by lowered transepithelial electrical resistance and mislocalization of the tight junction protein ZO-1 after calcium switch. The knock down of Lin-7 also resulted in the loss of expression of several Lin-7 binding partners, including PALS1 and the polarity protein PATJ. The effects of Lin-7 knock down were rescued by the exogenous expression of murine Lin-7 constructs that contained the L27 domain, but not the PDZ domain alone. Furthermore, exogenously expressed PALS1, but not other Lin-7 binding partners, also rescued the effects of Lin-7 knock down, including the restoration of PATJ protein in rescued cell lines. Finally, the effects of Lin-7 knock down appeared to be due to instability of PALS1 protein in the absence of Lin-7, as indicated by an increased rate of PALS1 protein degradation. Taken together, these results indicate that Lin-7 functions in tight junction formation by stabilizing its membrane-associated guanylate kinase binding partner PALS1. 相似文献
5.
Establishment of epithelial apicobasal polarity is crucial for proper kidney development and function. In recent years, there have been important advances in our understanding of the factors that mediate the initiation of apicobasal polarization. Key among these are the polarity complexes that are evolutionarily conserved from simple organisms to humans. Three of these complexes are discussed in this review: the Crumbs complex, the Par complex, and the Scribble complex. The apical Crumbs complex consists of three proteins, Crumbs, PALS1, and PATJ, whereas the apical Par complex consists of Par-3, Par-6, and atypical protein kinase C. The lateral Scribble complex consists of Scribble, discs large, and lethal giant larvae. These complexes modulate kinase and small G protein activity such that the apical and basolateral complexes signal antagonistically, leading to the segregation of the apical and basolateral membranes. The polarity complexes also serve as scaffolds to direct and retain proteins at the apical membrane, the basolateral membrane, or the intervening tight junction. There is plasticity in apicobasal polarity, and this is best seen in the processes of epithelial-to-mesenchymal transition and the converse mesenchymal-to-epithelial transition. These transitions are important in kidney disease as well as kidney development, and modulation of the polarity complexes are critical for these transitions. 相似文献
6.
Genomewide identification of genes involved in the potato response to drought indicates functional evolutionary conservation with Arabidopsis plants 总被引:1,自引:0,他引:1
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7.
JN Matthiessen 《Australian Journal of Entomology》1999,38(4):348-353
In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival. 相似文献
8.
BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response 相似文献
9.
A recirculation loop added to a large-scale roller bottle reactor resulted in high cell densities as compared to standard roller bottles. Four different mammalian cell lines reached an average maximum density equal to 5.4 x 10(6) cells /mL (sigma = 0.263), which was between 2.13 and 2.95 times greater than the densities in roller bottles without recirculation using the same cell lines. The high densities were maintained over long durations (>25 days) while the reactor operated with continuous perfusion. The increased densities are attributed to enhanced liquid mixing and oxygen transfer that occur as a result of the recirculation loop. Models were developed that describe axial liquid flow and oxygen transfer in both the sample loop and the reactor growth chamber. Axial dispersion and oxygen transfer coefficients are presented for a variety of operating conditions. The increased oxygen transfer characteristics of the reactor allow for easy scale-up of roller bottle cultures by operating at larger volumes with greater liquid depths than conventional roller bottles permit. The surface-area-to-volume ratio in the tests performed was 0.206 versus 1.16 cm(-1) in a standard roller bottle. 相似文献
10.
Florian Ryffel Eric JN Helfrich Patrick Kiefer Lindsay Peyriga Jean-Charles Portais J?rn Piel Julia A Vorholt 《The ISME journal》2016,10(3):632-643
The phyllosphere, which is defined as the parts of terrestrial plants above the ground, is a large habitat for different microorganisms that show a high extent of adaption to their environment. A number of hypotheses were generated by culture-independent functional genomics studies to explain the competitiveness of specialized bacteria in the phyllosphere. In contrast, in situ data at the metabolome level as a function of bacterial colonization are lacking. Here, we aimed to obtain new insights into the metabolic interplay between host and epiphytes upon colonization of Arabidopsis thaliana leaves in a controlled laboratory setting using environmental metabolomics approaches. Quantitative nuclear magnetic resonance (NMR) and imaging high-resolution mass spectrometry (IMS) methods were used to identify Arabidopsis leaf surface compounds and their possible involvement in the epiphytic lifestyle by relative changes in compound pools. The dominant carbohydrates on the leaf surfaces were sucrose, fructose and glucose. These sugars were significantly and specifically altered after epiphytic leaf colonization by the organoheterotroph Sphingomonas melonis or the phytopathogen Pseudomonas syringae pv. tomato, but only to a minor extent by the methylotroph Methylobacterium extorquens. In addition to carbohydrates, IMS revealed surprising alterations in arginine metabolism and phytoalexin biosynthesis that were dependent on the presence of bacteria, which might reflect the consequences of bacterial activity and the recognition of not only pathogens but also commensals by the plant. These results highlight the power of environmental metabolomics to aid in elucidating the molecular basis underlying plant–epiphyte interactions in situ. 相似文献