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51.
Tel-1 Transposon-like Elements of Tetrahymena Thermophila Are Associated with Micronuclear Genome Rearrangements 下载免费PDF全文
The micronuclear genome of Tetrahymena thermophila contains Tel-1 elements that structurally resemble transposons. Here we present molecular evidence that Tel-1 transposon-like elements are mobile. The arrangements of Tel-1 elements in the micronuclear genomes of several T. thermophila strains and cell lines were assayed by Southern blotting. The molecular evidence for Tel-1 transposition is most striking in strains that have undergone unusual laboratory-induced meioses. The genetic history of the strains exhibiting evidence of Tel-1 transposition is consistent with periods of genome restructuring in response to genomic ``shock' that B. McClintock has suggested could result in transposon activation. 相似文献
52.
Perception of the auxin signal at the plasma membrane of tobacco mesophyll protoplasts 总被引:6,自引:0,他引:6
Hélène Barbier-Brygoo Geneviève Ephritikhine Dieter Klämbt Christophe Maurel Klaus Palme Jeff Schell Jean Guern 《The Plant journal : for cell and molecular biology》1991,1(1):83-93
Auxin-induced variations of transmembrane potential difference have been shown to be a useful tool for analyzing hormone sensitivity in tobacco protoplasts. Using this technique, we demonstrated that protoplasts derived from wild-type, an auxin-resistant mutant and Agrobacterium-rhizogenes transformed plants differed widely in the sensitivity of their electrical response to naphthalene acetic acid. We have used different antibodies, raised to auxin binding proteins (ABP) from maize coleoptiles, or to the axr1 gene product (ABP1), to test whether changes in auxin sensitivity can be correlated with the presence of tobacco proteins immunologically related to this ABP. Titrations indicated that 0.4 nM anti-ABP IgG inhibited 50% of the auxin-specific response of wild-type protoplasts, whereas 0.04 nM or 4 nM anti-ABP IgG were necessary to inhibit the response of mutant and transformed protoplasts, respectively, to the same extent. On wild-type protoplasts, blocking part of the immunoreactive sites with anti-ABP antibodies resulted in a decrease in auxin sensitivity of the electrical response (0.4 nM anti-ABP IgG inducing a 10–fold decrease), whereas addition of maize ABP increased this auxin sensitivity (1 pM ABP1 raised the sensitivity more than 1000–fold). The results obtained suggest that the auxin sensitivity detected by our assay system correlates with the amount of tobacco proteins immunologically related to the axr1 gene product from maize. A hypothesis accounting for the presence of these proteins at the external surface of tobacco protoplasts and for the effects of hetero-logous maize ABP on auxin sensitivity is proposed. 相似文献
53.
Charles D. Hébert Sumiyo Endo Kenneth S. Korach Jeff Boyd J. Carl Barrett John A. Mclachlan Retha R. Newbold 《In vitro cellular & developmental biology. Animal》1992,28(5):327-336
Neonatal treatment with estrogens is associated with development of uterine adenocarcinomas in CD-1 mice. Treatment with the
synthetic estrogen diethylstilbestrol (DES) on Days 1 to 5 after birth results in 90% incidence of these hormonedependent
lesions in 18-mo.-old mice. Three cell lines were established from these DES-associated tumors. Each of these cell lines exhibited
morphologic and ultrastructural characteristics of transformed epithelial cells, including an increased nuclear:ytoplasmic
ratio, enlarged and irregular nuclei with multiple nucleoli and areas of chromatin condensation, positive staining for cytokeratin,
desmosomes, and microvilli. After subcutaneous injection into nude mice, all three cell lines formed solid tumors within 4
wk. Although the primary uterine tumors and tumor transplants in nude mice had been shown to be estrogen-dependent and estrogen-receptor
positive, neither the monolayer growth nor the tumorigenicity of any of the three cell lines in this study was enhanced by
or dependent on estrogen. Estrogen receptor levels were low in early and intermediate passage cells. Allele-specific oligonucleotide
hybridization analysis of PCR-amplified cell line DNA revealed no point mutations in the 12th, 13th, or 61st codons of the
K-ras or H-ras protooncogenes. Southern analysis revealed no changes in genomic organization of the putative tumor suppressor
gene DCC, but demonstrated a three-to four-fold amplification of the c-myc gene in one cell line. Expression of c-myc RNA
was concomitantly increased in the same cell line. These three transformed cell lines represent the end point in the process
of hormone-associated tumorigenesis and as such should prove useful in investigating the molecular changes and the mechanisms
involved in hormonal carcinogenesis. 相似文献
54.
CHLOROPLAST DNA POLYMORPHISM AND PHYLOGENY IN THE B GENOME OF GLYCINE SUBGENUS GLYCINE (LEGUMINOSAE)
The B genome of Glycine subgenus Glycine comprises three diploid species whose monophyly is supported by morphological, crossing, and chloroplast DNA (cpDNA) data. Previous cpDNA studies indicated low levels of divergence among these taxa and failed to resolve cladistic relationships among them. More intensive studies of cpDNA variation were initiated, using additional restriction endonucleases and accessions. Results from cladistic analyses of over 50 restriction site characters indicate that there is considerable cpDNA polymorphism within this group of species, with a minimum of 27 plastome types occurring among the 74 accessions sampled. Levels of homoplasy observed in this group are relatively high (15%) for closely related congeneric species. There is only limited congruence between plastome type and taxonomic classification based on morphological characters. Explanations for this lack of concordance include: 1) the early state of taxonomic understanding in this group, 2) lack of resolution in the cpDNA tree caused by homoplasy and the small number of synapomorphic characters, 3) introgression among these interfertile, often sympatric taxa, and 4) maintenance of ancestral cpDNA polymorphisms resulting in shared plastomes among species. 相似文献
55.
56.
Restriction endonucleases EcoRI and HindIII generated fragments of T4 cytosine-containing DNA were inserted into bacteriophage vector λgtSuIII and plasmid vectors pMB9 and pBR313. Resulting clones were screened for hybridization with 32P labeled T4 tRNA. Recombinant bacteriophages and plasmids were isolated which contained a T4 fragment coding for T4 RNA species 1 and 2 and T4 tRNAArg. Selected λ-T4 hybrid bacteriophages were grown to high titer and their DNA analyzed by gel electrophoresis. 相似文献
57.
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59.
Maitreyi Sur Brian Woodbridge Todd C. Esque Jim R. Belthoff Peter H. Bloom Robert N. Fisher Kathleen Longshore Kenneth E. Nussear Jeff A. Tracey Melissa A. Braham Todd E. Katzner 《Ecology and evolution》2021,11(12):7905
- A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat‐specific behaviors.
- Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation‐relevant habitat associations.
- We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short‐distance movement behaviors characterized by low AGL (state 1 AGL = 14 m (median); state 2 AGL = 11 m) and two associated with longer‐distance movement behaviors and characterized by higher AGL (state 3 AGL = 108 m; state 4 AGL = 450 m).
- Behaviors such as perching and low‐altitude hunting were associated with short‐distance movements in updraft‐poor environments, at higher elevations, and over steeper and more north‐facing terrain. In contrast, medium‐distance movements such as hunting and transiting were over gentle and south‐facing slopes. Long‐distance transiting occurred over the desert habitats that generate the best updraft.
- This information can guide management of this species, and our approach provides a template for behavior‐specific habitat associations for other species of management concern.
60.
Keng Po Lai Xiao Lin Nathan Tam Jeff Cheuk Hin Ho Marty Kwok-Shing Wong Jie Gu Ting Fung Chan William Ka Fai Tse 《Environmental microbiology》2020,22(9):3784-3802
Alteration of the gut microbiota plays an important role in animal health and metabolic diseases. However, little is known with respect to the influence of environmental osmolality on the gut microbial community. The aim of the current study was to determine whether the reduction in salinity affects the gut microbiota and identify its potential role in salinity acclimation. Using Oryzias melastigma as a model organism to perform progressive hypotonic transfer experiments, we evaluated three conditions: seawater control (SW), SW to 50% sea water transfer (SFW) and SW to SFW to freshwater transfer (FW). Our results showed that the SFW and FW transfer groups contained higher operational taxonomic unit microbiota diversities. The dominant bacteria in all conditions constituted the phylum Proteobacteria, with the majority in the SW and SFW transfer gut comprising Vibrio at the genus level, whereas this population was replaced by Pseudomonas in the FW transfer gut. Furthermore, our data revealed that the FW transfer gut microbiota exhibited a reduced renin–angiotensin system, which is important in SW acclimation. In addition, induced detoxification and immune mechanisms were found in the FW transfer gut microbiota. The shift of the bacteria community in different osmolality environments indicated possible roles of bacteria in facilitating host acclimation. 相似文献