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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.
相似文献
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.
相似文献
3.
Steinhour E Sherwani SI Mazerik JN Ciapala V O'Connor Butler E Cruff JP Magalang U Parthasarathy S Sen CK Marsh CB Kuppusamy P Parinandi NL 《Molecular and cellular biochemistry》2008,315(1-2):97-112
We have earlier reported that the redox-active antioxidant, vitamin C (ascorbic acid), activates the lipid signaling enzyme, phospholipase D (PLD), at pharmacological doses (mM) in the bovine lung microvascular endothelial cells (BLMVECs). However, the activation of phospholipase A(2) (PLA(2)), another signaling phospholipase, and the modulation of PLD activation by PLA(2) in the ECs treated with vitamin C at pharmacological doses have not been reported to date. Therefore, this study aimed at the regulation of PLD activation by PLA(2) in the cultured BLMVECs exposed to vitamin C at pharmacological concentrations. The results revealed that vitamin C (3-10 mM) significantly activated PLA(2) starting at 30 min; however, the activation of PLD resulted only at 120 min of treatment of cells under identical conditions. Further studies were conducted utilizing specific pharmacological agents to understand the mechanism(s) of activation of PLA(2) and PLD in BLMVECs treated with vitamin C (5 mM) for 120 min. Antioxidants, calcium chelators, iron chelators, and PLA(2) inhibitors offered attenuation of the vitamin C-induced activation of both PLA(2) and PLD in the cells. Vitamin C was also observed to significantly induce the formation and release of the cyclooxygenase (COX)- and lipoxygenase (LOX)-catalyzed arachidonic acid (AA) metabolites and to activate the AA LOX in BLMVECs. The inhibitors of PLA(2), COX, and LOX were observed to effectively and significantly attenuate the vitamin C-induced PLD activation in BLMVECs. For the first time, the results of the present study revealed that the vitamin C-induced activation of PLD in vascular ECs was regulated by the upstream activation of PLA(2), COX, and LOX through the formation of AA metabolites involving oxidative stress, calcium, and iron. 相似文献
4.
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
5.
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
6.
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
7.
One of the most abundant components of the enterocyte brush border is the actin-based monomeric motor, myosin-1a (Myo1a). Within brush border microvilli, Myo1a carries out a number of critical functions at the interface between membrane and actin cytoskeleton. Proper physiological function of Myo1a depends on its ability to bind to microvillar membrane, an interaction mediated by a C-terminal tail homology 1 (TH1) domain. However, little is known about the mechanistic details of the Myo1a-TH1/membrane interaction. Structure-function analysis of Myo1a-TH1 targeting in epithelial cells revealed that an N-terminal motif conserved among class I myosins and a C-terminal motif unique to Myo1a-TH1 are both required for steady state microvillar enrichment. Purified Myo1a bound to liposomes composed of phosphatidylserine and phosphoinositol 4,5-bisphosphate, with moderate affinity in a charge-dependent manner. Additionally, peptides of the N- and C-terminal regions required for targeting were able to compete with Myo1a for binding to highly charged liposomes in vitro. Single molecule total internal reflection fluorescence microscopy showed that these motifs are also necessary for slowing the membrane detachment rate in cells. Finally, Myo1a-TH1 co-localized with both lactadherin-C2 (a phosphatidylserine-binding protein) and PLCδ1-PH (a phosphoinositol 4,5-bisphosphate-binding protein) in microvilli, but only lactaderin-C2 expression reduced brush border targeting of Myo1a-TH1. Together, our results suggest that Myo1a targeting to microvilli is driven by membrane binding potential that is distributed throughout TH1 rather than localized to a single motif. These data highlight the diversity of mechanisms that enable different class I myosins to target membranes in distinct biological contexts. 相似文献
8.
Background
During the development of the central nervous system (CNS), patterning processes along the dorsoventral (DV) axis of the neural tube generate different neuronal subtypes. As development progresses these neurons are arranged into functional units with varying cytoarchitecture, such as laminae or nuclei for efficient relaying of information. Early in development ventral and dorsal regions are similar in size and structure. Different proliferation rates and cell migration patterns are likely to result in the formation of laminae or nuclei, eventually. However, the underlying molecular mechanisms that establish these different structural arrangements are not well understood. 相似文献9.
Efficient four fragment cloning for the construction of vectors for targeted gene replacement in filamentous fungi 总被引:2,自引:0,他引:2
Rasmus JN Frandsen Jens A Andersson Matilde B Kristensen Henriette Giese 《BMC molecular biology》2008,9(1):70
Background
The rapid increase in whole genome fungal sequence information allows large scale functional analyses of target genes. Efficient transformation methods to obtain site-directed gene replacement, targeted over-expression by promoter replacement, in-frame epitope tagging or fusion of coding sequences with fluorescent markers such as GFP are essential for this process. Construction of vectors for these experiments depends on the directional cloning of two homologous recombination sequences on each side of a selection marker gene. 相似文献10.