共查询到20条相似文献,搜索用时 67 毫秒
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脉孢菌lca-1基因调控无性产孢及类胡萝卜素的合成 总被引:1,自引:0,他引:1
类胡萝卜素是很多生物细胞内重要的抗氧化剂,具有保护细胞免受紫外线伤害的功能。粗糙脉孢菌是少数几个类胡萝卜素合成基因比较清楚的真菌之一,为了深入了解该菌类胡萝卜素合成调控机制,通过对粗糙脉孢菌基因突变体库中6,087株突变体进行筛选,新发现6个基因敲除突变体营养生长正常,但类胡萝卜素的合成降低,其中表型较好的1个突变体,其无性产孢量与类胡萝卜素合成量均明显降低。鉴定发现该突变体所缺失的基因编码一种依赖ATP的染色体重建复合体的ATP酶链ISW1,将该基因命名为lca-1。进一步测定发现lca-1基因的突变导 相似文献
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We are developing budding yeast, Saccharomyces cerevisiae, as a genetic system for the study of tolerance to the trivalent aluminum cation (Al3+). We have isolated eight mutants that are more sensitive to Al3+ than the wild type. Each mutant represented a different complementation group. A number of the mutants were pleiotropic,
and showed defects in other stress responses, changes in tolerance to other metal cations, or abnormal morphology. Two mutants
also showed increased dependence on supplemental Mg2+ and Ca2+. One mutant with a relatively specific sensitivity to Al3+ was chosen for molecular complementation. Normal Al3+ tolerance was restored by expression of the MAP kinase gene SLT2. Strains carrying deletions of the SLT2 gene, or of the gene for the corresponding MAP kinase–kinase SLK1, showed sensitivity to Al3+. These results indicate that the SLT2 MAP kinase signal transduction pathway is required for yeast to sense and respond to Al3+ stress.
Received: 17 April 1996 / Accepted: 21 October 1996 相似文献
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《Molecular & general genetics : MGG》1998,258(1-2):78-88
The gene cluster (ery) governing the biosynthesis of the macrolide antibiotic erythromycin A by Saccharopolyspora erythraea contains, in addition to the eryA genes encoding the polyketide synthase, two regions containing genes for later steps in the pathway. The region 5′ of eryA that lies between the known genes ermE (encoding the erythromycin resistance methyltransferase) and eryBIII (encoding a putative S-adenosylmethionine-dependent methyltransferase), and that contains the gene eryBI (orf2), has now been sequenced. The inferred product of the eryBI gene shows striking sequence similarity to authentic β-glucosidases. Specific mutants were created in eryBI, and the resulting strains were found to synthesise erythromycin A, showing that this gene, despite its position in the biosynthetic
gene cluster, is not essential for erythromycin biosynthesis. A␣mutant in eryBIII and a double mutant in eryBI and eryBIII were obtained and the analysis of novel erythromycins produced by these strains confirmed the proposed function of EryBIII
as a C-methyltransferase. Also, a chromosomal mutant was constructed for the previously sequenced ORF19 and shown to accumulate
erythronolide B, as expected for an eryB mutant and consistent with its proposed role as an epimerase in dTDP-mycarose biosynthesis.
Received: 13 August 1997 / Accepted: 27 November 1997 相似文献
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Genetic analysis of sterile mutants in the dpy-5 unc-13 (I) genomic region of Caenorhabditis elegans
Essential genes were identified in the 1.5-map unit dpy-5 unc-13 region of chromosome I in the Caenorhabditis elegans genome by rescuing lethal mutations using the duplication sDp2. In this paper, we report the mapping and complementation testing of lethal mutations, 45 of which identify 18 new, essential
genes. This analysis brings the number of essential genes defined by the sDp2 rescue of lethal mutants to 97; 64 of these map between dpy-5 and unc-13. 61% of these essential genes are identified by more than one allele. Positioning of the mutations was done using the breakpoints
of six duplications. The mutant phenotypes of 14 loci essential for fertility were characterized by Nomarski microscopy and
DAPI staining. None of the mutants were rescued by wild-type male sperm. The cytological data showed that four genes produced
mutants with defects in gonadogenesis, let-395, let-603, let-605 and let-610. Mutations in seven genes, let-355, let-367, let-384, let-513, let-544, let-545 and let-606, affected germ cell proliferation or gametogenesis. Mutants for the remaining three genes, let-370, let-599 and let-604, produced eggs that failed to develop or hatch, thereby acting as maternal effect lethals. We observed a nonrandom distribution
of arrest phenotypes with regard to map position.
Received: 8 May 1996 / Accepted : 27 January 1997 相似文献
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Two genes of Aspergillus nidulans are known to function in UV mutagenesis, but have been assigned to different epistasis groups: uvsC, which is also required for meiosis and mitotic recombination, and uvsI, which may have no other function. To clarify their role in error-prone repair and to investigate their interaction, uvsI and uvsC single and uvsI;uvsC double mutant strains were further tested for mutagen sensitivities and characterized for effects on mutation. Spontaneous
and induced frequencies were compared in forward and reverse mutation assays. All results confirmed that uvsI and uvsC are members of different epistasis groups, and demonstrated that these uvs mutants have very different defects in UV mutagenesis. The uvsI strains showed wild-type frequencies in all forward mutation tests, but greatly reduced spontaneous and UV-induced reversion of some, but not other, point mutations. In contrast, uvsC had similar effects in all assay systems: namely pronounced mutator effects and greatly reduced UV mutagenesis. Interestingly, the uvsI;uvsC double mutant strains differed from both single mutants; they clearly showed synergism for all types of reversion tested:
none were ever obtained spontaneously, nor after induction by UV or EMS (ethylmethane sulfonate). Based on these results,
we conclude that uvsI is active in a mutation-specific, specialized error-prone repair process in Aspergillus. In contrast, uvsC, which is now known to show sequence homology to recA, has a basic function in mutagenic UV repair in addition to recombinational repair, similar to recA of Escherichia coli.
Received: 23 September 1996 / Accepted: 2 December 1996 相似文献
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J. T. Kemp M. K. Balasubramanian K. L. Gould 《Molecular & general genetics : MGG》1997,254(2):127-138
The organization of the actin cytoskeleton plays an integral role in cell morphogenesis of all eukaryotes. We have isolated
a temperature-sensitive mutant in Schizosaccharomyces pombe, wat1-1, in which acting patches are delocalized, resulting in an elliptically shaped cell phenotype. Molecular cloning and DNA sequencing
of wat1
+ showed that the gene encodes a 314 residue protein containing WD-40 repeats. Cells lacking wat1
+ are slow growing but viable at 25° C and temperature-sensitive for growth above 33° C. At restrictive temperature, wat1-d strains are phenotypically indistinguishable from wat1-1. When combined with a deletion for the wat1
+ gene, cdc mutants failed to elongate at restrictive temperature and exhibited alterations in actin patch localization. This
analysis suggests that wat1
+ is required directly or indirectly for polarized cell growth in S. pombe. Wat1p and a functional, epitope-tagged, version of Wat1p can be overproduced without inducing alterations in cell morphology.
Received: 18 September 1996 / Accepted: 22 October 1996 相似文献
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《Molecular & general genetics : MGG》1997,256(3):239-251
The gene cluster (ery) governing the biosynthesis of the macrolide antibiotic erythromycin A by Saccharopolyspora erythraea contains, in addition to the eryA genes encoding the polyketide synthase, two regions containing genes for later steps in the pathway. The region 5′ of eryA, and lying between eryA and the gene eryK, which is known to encode the C-12 hydroxylase, has been sequenced and shown to contain seven additional open reading frames
(ORFs 13–19). On the basis of sequence similarities, roles are proposed for several of these ORFs in the biosynthesis of the
deoxysugar mycarose and the deoxyaminosugar desosamine. A chromosomal mutant carrying a deletion in ORF15 has been constructed
and shown to accumulate 3-O-mycarosyl-erythronolide B, as expected for an eryC mutant. Similarly, a chromosomal mutant carrying a deletion in ORF16 has been constructed and shown to accumulate erythronolide
B, as expected for an eryB mutant.
Received: 10 March 1997 / Accepted: 12 June 1997 相似文献
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S. Ohshima M. Murata W. Sakamoto Y. Ogura F. Motoyoshi 《Molecular & general genetics : MGG》1997,254(2):186-194
The Arabidopsis gene Terminal Flower 1 (TFL1) controls inflorescence meristem identity. A terminal flower (tfl1) mutant, which develops a terminal flower at the apex of the inflorescence, was induced by transformation with T-DNA. Using
a plant DNA fragment flanking the integrated T-DNA as a probe, a clone was selected from a wild-type genomic library. Comparative
sequence analysis of this clone with an EST clone (129D7T7) suggested the existence of a gene encoding a protein similar to
that encoded by the cen gene which controls inflorescence meristem identity in Antirrhinum. Nucleotide sequences of the region homologous to this putative TFL1 gene were compared between five chemically induced tfl1 mutants and their parental wild-type ecotypes. Every mutant was found to have a nucleotide substitution which could be responsible
for the tfl1 phenotype. This result confirmed that the cloned gene is TFL1 itself. In our tfl1 mutant, no nucleotide substitution was found in the transcribed region of the gene, and the T-DNA-insertion site was located
at 458 bp downstream of the putative polyadenylation signal, suggesting that an element important for expression of the TFL1 gene exists in this area.
Received: 14 November 1996 / Accepted: 29 November 1996 相似文献
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Identification of transposon-like elements in non-coding regions of tomato ACC oxidase genes 总被引:4,自引:0,他引:4
B. Blume C. S. Barry A. J. Hamilton M. Bouzayen D. Grierson 《Molecular & general genetics : MGG》1997,254(3):297-303
1-aminocyclopropane-1-carboxylate (ACC) oxidase, which catalyses the terminal step in ethylene biosynthesis, is encoded by
a small multigene family in tomato that is differentially expressed in response to developmental and environmental cues. In
this study we report the isolation and sequencing of approximately 2 kb of 5′-flanking sequence of three tomato ACC oxidase
genes (LEACO1, LEACO2, LEACO3) and the occurrence of class I and class II mobile element-like insertions in promoter and intron regions of two of them.
The LEACO1 upstream region contains a 420-bp direct repeat which is present in multiple copies in the tomato genome and is very similar
to sequences in the promoters of the tomato E4 and 2A11 genes. The region covering the repeats resembles the remnant of a retrotransposon. Two copies of a small transposable element,
belonging to the Stowaway inverted repeat element family, have been found in the 5′-flanking sequence and the third intron of LEACO3.
Received: 8 August 1996 / Accepted: 4 November 1996 相似文献
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M. Shimanuki F. Miki D.-Q. Ding Y. Chikashige Y. Hiraoka T. Horio O. Niwa 《Molecular & general genetics : MGG》1997,254(3):238-249
In the meiotic prophase nucleus of the fission yeast Schizosaccharomyces pombe, chromosomes are arranged in an oriented manner: telomeres cluster in close proximity to the spindle pole body (SPB), while
centromeres form another cluster at some distance from the SPB. We have isolated a mutant, kms1, in which the structure of the meiotic prophase nucleus appears to be distorted. Using specific probes to localize the SPB
and telomeres, multiple signals were observed in the mutant nuclei, in contrast to the case in wild-type. Genetic analysis
showed that in the mutant, meiotic recombination frequency was reduced to about one-quarter of the wild-type level and meiotic
segregation was impaired. This phenotype strongly suggests that the telomere-led rearrangement of chromosomal distribution
that normally occurs in the fission yeast meiotic nucleus is an important prerequisite for the efficient pairing of homologous
chromosomes. The kms1 mutant was also impaired in karyogamy, suggesting that the kms1
+ gene is involved in SPB function. However, the kms1
+ gene is dispensable for mitotic growth. The predicted amino acid sequence of the gene product shows no significant similarity
to known proteins.
Received: 5 September 1996 / Accepted: 21 November 1996 相似文献
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The unstable linear chromosome of Streptomyces lividans was circularized by homologous recombination and its terminal inverted repeats deleted. Strains with circularized chromosomes
showed no obvious phenotypic disadvantages compared to the wild type. However, they segregated about 20 times more chloramphenicol-sensitive
mutants than the wild type (24.3% vs. 1.4%), due to a higher incidence of large deletions. In addition, in all circularized
chromosomes amplification of 30–60 kb fragments was observed at the new chromosomal junction, to levels of approximately 10
copies per chromosome. Arginine auxotrophs that arose spontaneously among the progeny of strains with a circularized chromosome
showed high-copy-number amplification of the DNA element AUD1, as also seen in mutants of the wild type. These observations
demonstrate that the circular form of the Streptomyces chromosome is more unstable than the linear one.
Received: 28 July 1996 / Accepted: 18 November 1996 相似文献
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Total proteins extracted from developmental mutants of Arabidopsis thaliana (L.) Heyhn. and from wild-type plants cultivated in the presence of various hormones were analyzed by two-dimensional (2-D)
gel electrophoresis. Computer analysis of 2-D gels followed by a statistical treatment of data allowed us to build a phenogram
that describes the biochemical distances between the different genotypes. Analysis of the 2-D electrophoresis data allowed
us to discriminate mutants in agreement with phenotypical and physiological traits. This biochemical analysis helped us to
develop a working hypothesis which led us to show that one developmental mutant (cri1 ) overaccumulates cytokinins.
Received: 5 August 1996 / Accepted: 11 December 1996 相似文献