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31.
Chandrika Ramadugu Bernard E. Pfeil Manjunath L. Keremane Richard F. Lee Ivan J. Maureira-Butler Mikeal L. Roose 《PloS one》2013,8(7)
Background
Genus Citrus (Rutaceae) comprises many important cultivated species that generally hybridize easily. Phylogenetic study of a group showing extensive hybridization is challenging. Since the genus Citrus has diverged recently (4–12 Ma), incomplete lineage sorting of ancestral polymorphisms is also likely to cause discrepancies among genes in phylogenetic inferences. Incongruence of gene trees is observed and it is essential to unravel the processes that cause inconsistencies in order to understand the phylogenetic relationships among the species.Methodology and Principal Findings
(1) We generated phylogenetic trees using haplotype sequences of six low copy nuclear genes. (2) Published simple sequence repeat data were re-analyzed to study population structure and the results were compared with the phylogenetic trees constructed using sequence data and coalescence simulations. (3) To distinguish between hybridization and incomplete lineage sorting, we developed and utilized a coalescence simulation approach. In other studies, species trees have been inferred despite the possibility of hybridization having occurred and used to generate null distributions of the effect of lineage sorting alone (by coalescent simulation). Since this is problematic, we instead generate these distributions directly from observed gene trees. Of the six trees generated, we used the most resolved three to detect hybrids. We found that 11 of 33 samples appear to be affected by historical hybridization. Analysis of the remaining three genes supported the conclusions from the hybrid detection test.Conclusions
We have identified or confirmed probable hybrid origins for several Citrus cultivars using three different approaches–gene phylogenies, population structure analysis and coalescence simulation. Hybridization and incomplete lineage sorting were identified primarily based on differences among gene phylogenies with reference to null expectations via coalescence simulations. We conclude that identifying hybridization as a frequent cause of incongruence among gene trees is critical to correctly infer the phylogeny among species of Citrus. 相似文献32.
Ito S Ihara T Tamura H Tanaka S Ikeda T Kajihara H Dissanayake C Abdel-Motaal FF El-Sayed MA 《FEBS letters》2007,581(17):3217-3222
The tomato saponin alpha-tomatine has been proposed to kill sensitive cells by binding to cell membranes followed by leakage of cell components. However, details of the modes of action of the compound on fungal cells are poorly understood. In the present study, mechanisms involved in alpha-tomatine-induced cell death of fungi were examined using a filamentous pathogenic fungus Fusarium oxysporum. alpha-Tomatine-induced cell death of F. oxysporum (TICDF) occurred only under aerobic conditions and was blocked by the mitochondrial F(0)F(1)-ATPase inhibitor oligomycin, the caspase inhibitor D-VAD-fmk, and protein synthesis inhibitor cycloheximide. Fungal cells exposed to alpha-tomatine showed TUNEL-positive nuclei, depolarization of transmembrane potential of mitochondria, and reactive oxygen species (ROS) accumulation. These results suggest that TICDF occurs through a programmed cell death process in which mitochondria play a pivotal role. Pharmacological studies using inhibitors suggest that alpha-tomatine activates phosphotyrosine kinase and monomeric G-protein signaling pathways leading to Ca(2+) elevation and ROS burst in F. oxysporum cells. 相似文献
33.
Eliahu Heldman Ayala Balan Ora Horowitz Sarit Ben-Zion Michael Torten 《FEBS letters》1985,180(2):243-248
Antiparaoxon immune sera were employed in a new immunoassay based on competition between acetylcholinesterase and antibodies for the binding ofparaoxon. Unlike radioimmunoassay, the new assay described herein can be extended to predict the feasibility of antibodies to confer in vivo protection of acetylcholinesterase against organophosphate poisoning. The toxicity of paraoxon was reduced in mice which were pre-injected with the immune sera. 相似文献
34.
A cell culture that preserves its phenotype up to the 20th passage was obtained from mouse submandibular salivary glands.
An analysis of the heterogeneous culture indicates the existence of several morphological types of cells, including small,
densely packed cells of cuboidal or polygonal shapes and large, rounded cells. Epithelial cells of the submandibular gland
cultured for several weeks were able to form tubular structures. Our studied cell culture of glandulocytes (cells of glandular
epithelium) was represented by K19- and NGF-positive cells. It is important to note that, using both immunocytochemical staining
and PCR, the expression of genes that encode the proinsulin and insulin proteins is revealed in the studied cell population. 相似文献
35.
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37.
In Population Genetics, two populations are distinguished from each other on the basis of the differences in the distributions
of the alleles at the locus or loci under consideration. These differences are measured by a “genetic distance” between the
two populations (not to be confused with genetic distance between two loci, which is based on recombination fractions) and
they play a major role in inferences at the population level. Several measures of genetic distance have been proposed by different
authors (Sanghvi 1953; Cavalli-Sforza and Edwards 1967; Jukes and Cantor 1969; Nei 1972; Kimura 1980; Reynoldset al 1983; reviews in Felsenstein 1991; Nei and Kumar 2000). Most of these measures are actually dissimilarity measures and not
mathematically true distance measures (B-Rao and Majumdar 1999). Independently, and much before the geneticists, statisticians
too were concerned with the idea of distinguishing between two (statistical) populations. In order to discriminate between
two populations on the basis of one or more characters, divergence measures like “Mahalanobis’D
2 statistic” or “Mahalanobis’ generalized distance” (1936) and “Bhattacharyya’s distance” (1943, 1946), Kullback-Leibler’s
divergence measure (1951) etc. have been proposed by statisticians. Mukherjee and Chattopadhyaya (1986) have mentioned measures
based on distances, association between two attributes and discrimination function. There are similarities between the distance
measures defined by applied scientists and by theoreticians. Felsenstein (1985) shows that three of the allele frequency-based
genetic distance measures were anticipated by Bhattacharyya (1946). Nei and Takezaki (1994) have also studied the effectiveness
of several genetic distance measures in the context of phylogenetic analysis, including Bhattacharyya’s distance measure. 相似文献
38.
Schmidt P Youhnovski N Daiber A Balan A Arsic M Bachschmid M Przybylski M Ullrich V 《The Journal of biological chemistry》2003,278(15):12813-12819
Treatment of bovine aortic microsomes containing active prostacyclin synthase (PGI(2) synthase) with increasing concentrations of peroxynitrite (PN) up to 250 microm of PN yielded specific staining of this enzyme on Western blots with antibodies against 3-nitrotyrosine (3-NT), whereas above 500 microm PN staining of additional proteins was also observed. Following treatment of aortic microsomes with 25 microm PN, PGI(2) synthase was about half-maximally nitrated and about half-inhibited. It was then isolated by gel electrophoresis and subjected to proteolytic digestion with several proteases. Digestion with thermolysin for 24 h provided a single specific peptide that was isolated by high performance liquid chromatography and identified as a tetrapeptide Leu-Lys-Asn-Tyr(3-nitro)-COOH corresponding to positions 427-430 of PGI(2) synthase. Its structure was established by precise mass determination using Fourier transform-ion cyclotron resonance-nanoelectrospray mass spectrometry and Edman microsequencing and ascertained by synthesis and mass spectrometric characterization of the authentic Tyr-nitrated peptide. Complete digestion by Pronase to 3-nitrotyrosine was obtained only after 72 h, suggesting that the nitrated Tyr-430 residue may be embedded in a tight fold around the heme binding site. These results provide evidence for the specific inhibition of PGI(2) synthase by nitration at Tyr-430 that may occur already at low levels of PN as a consequence of endothelial co-generation of nitric oxide and superoxide. 相似文献
39.
40.
Leon V. Backinowsky Nikolay F. Balan Vitali I. Betaneli Nikolay K. Kochetkov 《Carbohydrate research》1982,99(2):189-193
The capsular polysaccharide from Klebsiella type K54, containing both O-formyl and O-acetyl groups, has been investigated by using the techniques of methylation analysis (by gas-liquid chromatography), periodate oxidation-Smith degradation, and both 1H- and 13C-n.m.r. spectroscopy. Degradation of the native polysaccharide with a bacteriophage-induced glucosidase generated a formylated, as well as a formylated and acetylated, tetrasaccharide, whereas similar depolymerization of the deacetylated polysaccharide yielded a single tetrasaccharide; the corresponding, O-acylated octasaccharides were also isolated and characterized. These oligosaccharides, utilized in chemical and spectroscopic studies in order to determine the location of the O-acyl substituents in the repeating sequence, indicated formylation at O-4 of each lateral d-glucosyl group and acetylation at O-2 of alternate l-fucosyl residues. A new structure for the repeating unit in the polysaccharide is proposed. 相似文献