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排序方式: 共有269条查询结果,搜索用时 109 毫秒
221.
Koltunow Anna M. Brennan Peter 《Molecular breeding : new strategies in plant improvement》1998,4(3):253-261
We have constructed chimaeric genes that are expressed in embryo and endosperm compartments of the seed, induce dominant seed lethality and have potential to reduce seed size in 75% of seeds within a fruit such as Citrus [7]. The genes are not entirely seed-specific as a proportion of primary test tobacco transformants containing their gene were fully male-sterile [7]. Here we investigated why a proportion of apparently male-fertile transgenic plants showed segregation distortion from the 75% seed lethality expected for a single dominant gene. Reciprocal crosses were conducted between pollen fertile, primary tobacco transformants containing various copies of the CG1-400-RNase gene [7] and wild-type tobacco plants to examine the transmission of the gene through maternal and paternal gametes and also the effects of gene dosage in embryo and endosperm compartments on seed viability and phenotype. Pollen viability, seed set and seed phenotype were examined over a 16 month period to assess stability of gene expression in primary transformants because woody, fruit crops containing these genes will be vegetatively propagated from primary transformants. In male-fertile transformants, the gene was observed to be expressed to varying degrees post-meiotically in pollen over the time period examined resulting in lethality of transgenic pollen and reduced paternal transmission. A variable, low-level maternal expression component was also detected that resulted in seed lethality and influenced morphological variation in the seed lethal phenotype. The maternal and paternal expression components caused seed lethality to range from 50 to 75%. This study indicates the need to select for transformants with stable pollen transmission and high seed expression and raises questions in relation to possible environmental and epistatic effects on gene expression in primary, hemizygous transformants over long growth periods. 相似文献
222.
Cell Differentiation and Morphogenesis Are Uncoupled in Arabidopsis raspberry Embryos 总被引:11,自引:6,他引:5
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Yadegari R Paiva G Laux T Koltunow AM Apuya N Zimmerman JL Fischer RL Harada JJ Goldberg RB 《The Plant cell》1994,6(12):1713-1729
We identified two Arabidopsis embryo mutants, designated as raspberry1 and raspberry2, by screening T-DNA-mutagenized Arabidopsis lines. Embryogenesis in these mutants is indistinguishable from that of wild-type plants until the late-globular stage, after which raspberry1 and raspberry2 embryos fail to undergo the transition to heart stage, remain globular shaped, and proliferate an enlarged suspensor region. raspberry1 and raspberry2 embryo-proper regions enlarge during embryogenesis, become highly vacuolate, and display prominent convex, or "raspberry-like" protuberances on their outer cell layers. In situ hybridization studies with several embryo cell-specific mRNA probes indicated that the raspberry1 and raspberry2 embryo-proper regions differentiate tissue layers in their correct spatial contexts and that the regulation of cell-specific genes within these layers is normal. Surprisingly, a similar spatial and temporal pattern of mRNA accumulation occurs within the enlarged suspensor region of raspberry1 and raspberry2 embryos, suggesting that a defect in embryo-proper morphogenesis can cause the suspensor to take on an embryo-proper-like state and differentiate a radial tissue-type axis. We conclude that cell differentiation can occur in the absence of both organ formation and morphogenesis during plant embryogenesis and that interactions occur between the embryo-proper and suspensor regions. 相似文献
223.
High copy number of highly similar mariner-like transposons in planarian (Platyhelminthe): evidence for a trans-phyla horizontal transfer 总被引:8,自引:2,他引:6
Garcia-Fernandez J; Bayascas-Ramirez JR; Marfany G; Munoz-Marmol AM; Casali A; Baguna J; Salo E 《Molecular biology and evolution》1995,12(3):421-431
Several DNA sequences similar to the mariner element were isolated and
characterized in the platyhelminthe Dugesia (Girardia) tigrina. They were
1,288 bp long, flanked by two 32 bp-inverted repeats, and contained a
single 339 amino acid open-reading frame (ORF) encoding the transposase.
The number of copies of this element is approximately 8,000 per haploid
genome, constituting a member of the middle- repetitive DNA of Dugesia
tigrina. Sequence analysis of several elements showed a high percentage of
conservation between the different copies. Most of them presented an intact
ORF and the standard signals of actively expressed genes, which suggests
that some of them are or have recently been functional transposons. The
high degree of similarity shared with other mariner elements from some
arthropods, together with the fact that this element is undetectable in
other planarian species, strongly suggests a case of horizontal transfer
between these two distant phyla.
相似文献
224.
Assessing horizontal transfer of nifHDK genes in eubacteria: nucleotide sequence of nifK from Frankia strain HFPCcI3 总被引:2,自引:1,他引:1
Hirsch AM; McKhann HI; Reddy A; Liao J; Fang Y; Marshall CR 《Molecular biology and evolution》1995,12(1):16-27
The structural genes for nitrogenase, nifK, nifD, and nifH, are crucial for
nitrogen fixation. Previous phylogenetic analysis of the amino acid
sequence of nifH suggested that this gene had been horizontally transferred
from a proteobacterium to the gram-positive/cyanobacterial clade, although
the confounding effects of paralogous comparisons made interpretation of
the data difficult. An additional test of nif gene horizontal transfer
using nifD was made, but the NifD phylogeny lacked resolution. Here nif
gene phylogeny is addressed with a phylogenetic analysis of a third and
longer nif gene, nifK. As part of the study, the nifK gene of the key taxon
Frankia was sequenced. Parsimony and some distance analyses of the nifK
amino acid sequences provide support for vertical descent of nifK, but
other distance trees provide support for the lateral transfer of the gene.
Bootstrap support was found for both hypotheses in all trees; the nifK data
do not definitively favor one or the other hypothesis. A parsimony analysis
of NifH provides support for horizontal transfer in accord with previous
reports, although bootstrap analysis also shows some support for vertical
descent of the orthologous nifH genes. A wider sampling of taxa and more
sophisticated methods of phylogenetic inference are needed to understand
the evolution of nif genes. The nif genes may also be powerful phylogenetic
tools. If nifK evolved by vertical descent, it provides strong evidence
that the cyanobacteria and proteobacteria are sister groups to the
exclusion of the firmicutes, whereas 16S rRNA sequences are unable to
resolve the relationships of these three major eubacterial lineages.
相似文献
225.
226.
Danyel GJ Jennen Addie LJ Vereijken Henk Bovenhuis Richard MPA Crooijmans Jan J van der Poel Martien AM Groenen 《遗传、选种与进化》2005,37(3):215-228
In this report we describe the analysis of an advanced intercross line (AIL) to confirm the quantitative trait locus (QTL) regions found for fatness traits in a previous study. QTL analysis was performed on chromosomes 1, 3, 4, 15, 18, and 27. The AIL was created by random intercrossing in each generation from generation 2 (G2) onwards until generation 9 (G9) was reached. QTL for abdominal fat weight (AFW) and/or percentage abdominal fat (AF%) on chromosomes 1, 3 and 27 were confirmed in the G9 population. In addition, evidence for QTL for body weight at the age of 5 (BW5) and 7 (BW7) weeks and for the percentage of intramuscular fat (IF%) were found on chromosomes 1, 3, 15, and 27. Significant evidence for QTL was detected on chromosome 1 for BW5 and BW7. Suggestive evidence was found on chromosome 1 for AFW, AF% and IF%, on chromosome 15 for BW5, and on chromosome 27 for AF% and IF%. Furthermore, evidence on the chromosome-wise level was found on chromosome 3 for AFW, AF%, and BW7 and on chromosome 27 for BW5. For chromosomes 4 and 18, test statistics did not exceed the significance threshold. 相似文献
227.
228.
Sara Castiglioni Clelia Caspani Alessandra Cazzaniga Jeanette AM Maier 《World journal of biological chemistry》2014,5(4):457-464
AIM: To study the response to silver nanoparticles (Ag NP) of human microvascular endothelial cells, protagonists of angiogenesis.METHODS: We cultured human microvascular endothelial cells and endothelial colony-forming cells in their corresponding growth medium. Stock solutions of Ag NP were prepared in culture medium and sonicated before use. They were added at different concentrations and for different times to culture media. The toxicity of Ag NP was investigated by measuring the reduction of yellow tetrazolium salt to dark purple formazan (MTT assay) at 575 nm. After staining with trypan blue, cell proliferation was assessed by counting viable cells. The lactate dehydrogenase leakage assay was performed on culture media by following the oxidation of NADH to NAD+ and monitoring the reaction kinetically at 340 nm. Reactive oxygen species production was quantified using 2’-7’-dichlorofluorescein diacetate. The alkaline comet assay was performed after mixing the cells with low melting-point agarose. Electrophoresis was then conducted and the samples were stained with ethidium bromide and analyzed with a fluorescence microscope.RESULTS: Ag NP are cytotoxic in a dose and time dependent fashion for HMEC. At high concentrations, Ag NP determine loss of membrane integrity as demonstrated by the increased activity of lactate dehydrogenase in the culture medium. Ag NP rapidly stimulate the formation of free radicals. However, pre-incubation with Trolox, apocynin, or N-acetyl-L-cysteine, antioxidants which have different structure and act through different mechanisms, is not sufficient to prevent cytotoxicity. Ag NP also induce DNA damage dose-dependently, as shown by comet assay. When exposed to sublethal concentrations of Ag NP for long times, the cells remain viable but are growth retarded. Interestingly, removal of Ag NP partially rescues cell growth. Also genotoxicity is reversible upon removal of Ag NP from culture medium, suggesting that no permanent modifications occur. It is noteworthy that Ag NP are cytotoxic and genotoxic also for endothelial progenitors, in particular for endothelial colony-forming cells, which participate to angiogenesis.CONCLUSION: Silver nanoparticles are cytotoxic and genotoxic for human microvascular endothelial cells and might become a useful tool to control excessive angiogenesis. 相似文献
229.
Sexual and apomictic seed formation in Hieracium requires the plant polycomb-group gene FERTILIZATION INDEPENDENT ENDOSPERM
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A Polycomb-Group (PcG) complex, FERTILIZATION INDEPENDENT SEED (FIS), represses endosperm development in Arabidopsis thaliana until fertilization occurs. The Hieracium genus contains apomictic species that form viable seeds asexually. To investigate FIS function during apomictic seed formation, FERTILIZATION INDEPENDENT ENDOSPERM (FIE), encoding a WD-repeat member of the FIS complex, was isolated and downregulated in sexual and apomictic Hieracium species. General downregulation led to defects in leaf and seed development, consistent with a role in developmental transitions and cell fate. PcG-like activity of Hieracium FIE was also supported by its interaction in vitro with the Arabidopsis CURLY LEAF PcG protein. By contrast, specific downregulation of FIE in developing seeds of sexual Hieracium did not result in autonomous endosperm proliferation but led to seed abortion after cross-pollination. Furthermore, in apomictic Hieracium, specific FIE downregulation inhibited autonomous embryo and endosperm initiation, and most autonomous seeds displayed defective embryo and endosperm growth. Therefore, FIE is required for both apomictic and fertilization-induced seed initiation in Hieracium. Since Hieracium FIE failed to interact with FIS class proteins in vitro, its partner proteins might differ from those in the FIS complex of Arabidopsis. These differences in protein interaction were attributed to structural modifications predicted from comparisons of Arabidopsis and Hieracium FIE molecular models. 相似文献
230.
Michelle I Portugal Adriane R Todeschini Cristiana S de Lima Carlos AM Silva Ronaldo Mohana-Borges Tom HM Ottenhoff Lucia Mendonça-Previato Jose O Previato Maria CV Pessolani 《BMC microbiology》2008,8(1):75