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1.
Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid (ABA) and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 (spcl-1) and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase (ZDS) in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development. 相似文献
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A mutant of Arabidopsis deficient in the chloroplast 16:1/18:1 desaturase 总被引:6,自引:11,他引:6 下载免费PDF全文
Leaf tissue of a mutant of Arabidopsis thaliana contains reduced levels of both 18-carbon and 16-carbon polyunsaturated fatty acids and increased levels of the 18:1 and cis-16:1 precursors due to a single nuclear mutation at a locus designated fadC. Analysis of the fatty acid compositions of individual lipids and the kinetics of lipid labeling with [14C]acetate in vivo indicate that the mutant lacks activity of the chloroplast glycerolipid ω-6 desaturase. As a result, lipids synthesized by the prokaryotic pathway are not desaturated further than 18:1 and 16:1. Lipids derived from the eukaryotic pathway are desaturated—presumably by the endoplasmic reticulum 18:1 phosphatidylcholine desaturase. However, an increase in the level of 18:1 on all the phospholipids derived from the eukaryotic pathway in leaves of the mutant suggests that the mutation does exert an effect on the composition of extrachloroplast membranes. Synthesis of monogalactosyldiacylglycerol (MGD) by the prokaryotic pathway is reduced 30 to 35% in the mutant and there is a corresponding increase in MGD synthesis by the eukaryotic pathway. This shift in metabolism which results in a more unsaturated MGD pool, may reflect the existence of a regulatory mechanism which apportions lipid synthesis between the two pathways in response to alterations in the physical properties of the chloroplast membranes. 相似文献
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N V Iakubovich N Iu Zemlianaia L M Ermakova I S Novikova M D Krylova 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1985,(1):17-22
Bacteriophage beta 45 of Corynebacterium diphtheriae was harvested. The extracted DNA of the bacteriophage was digested by the restriction endonuclease BamHI and inserted into the BamHI cleavage site of pUC19 vector plasmid. Plasmid pNVY5 containing a mutant gene crm45 of diphtheriae toxin in a 3.9 bpn fragment was isolated from the hybrid plasmids obtained. Cell free extracts of E. coli strain TG1 (pVNY5) contain the nontoxic protein crm45 possessing the specific enzymatic activity of diphtheriae toxin (ADP ribosylation on wheat elongation factor two). According to orientation of BamHI fragment in pNVY5 plasmid it is concluded that the crm45 gene is expressed using its own promoter. 相似文献
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Lacombe S Kaan F Léger S Bervillé A 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》2001,324(9):839-845
All the [HOAC] lines derived from the Pervenets mutant carry a specific RFLP (oleHOS) revealed by an oleate desaturase cDNA used as a probe. The [LO] (linoleic) genotypes do not carry oleHOS, but another allele: oleLOR. We studied [HOAC] heredity in two segregating populations. In an F2 population, the [HOAC] trait co-segregated with oleHOS. In a recombinant inbred line F6 population, all [HOAC] RI lines carried oleHOS. The RI lines carrying oleHOS were either [LO] or [HOAC]. The absence of [HOAC] RI lines with oleLOR eliminated the occurrence of a recombination event between the locus carrying oleHOS and the locus carrying Pervenets allele. The [HOAC] trait is due to 2 independent loci: the locus carrying oleHOS allele and another locus. One allele at this other locus may suppress the effect of oleHOS allele on the [HOAC] trait. The existence of this suppressor allele has only been suggested for sunflower. 相似文献
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Claire Domon Jean-Luc Evrard Datta T.N. Pillay André Steinmetz 《Molecular & general genetics : MGG》1991,229(2):238-244
Summary Metabolism of sulfonylurea herbicides by Streptomyces griseolus ATCC 11796 is carried out via two cytochromes P-450, P-450SU1 and P-450SU2. Mutants of S. griseolus, selected by their reduced ability to metabolize a fluorescent sulfonylurea, do not synthesize cytochrome P-450SU1 when grown in the presence of sulfonylureas. Genetic evidence indicated that this phenotype was the result of a deletion of > 15 kb of DNA, including the structural genes for cytochrome P-450SU1 and an associated ferredoxin Fd-1 (suaC and suaB, respectively). In the absence of this monooxygenase system, the mutants described here respond to the presence of sulfonylureas or phenobarbital in the growth medium with the expression of only the suhC,B gene products (cytochrome P-450SU2 and Fd-2), previously observed only as minor components in wild-type cells treated with sulfonylurea. These strains have enabled an analysis of sulfonylurea metabolism mediated by cytochrome P-450SU2 in the absence of P-450SU1, yielding an in vivo delineation of the roles of the two different cytochrome P-450 systems in herbicide metabolism by S. griseolus. 相似文献
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The OLE1 gene of Saccharomyces cerevisiae encodes the delta 9 fatty acid desaturase and can be functionally replaced by the rat stearoyl-CoA desaturase gene 总被引:10,自引:0,他引:10
Strains of Saccharomyces cerevisiae bearing the ole1 mutation are defective in unsaturated fatty acid (UFA) synthesis and require UFAs for growth. A previously isolated yeast genomic fragment complementing the ole1 mutation has been sequenced and determined to encode the delta 9 fatty acid desaturase enzyme by comparison of primary amino acid sequence to the rat liver stearoyl-CoA desaturase. The OLE1 structural gene encodes a protein of 510 amino acids (251 hydrophobic) having an approximate molecular mass of 57.4 kDa. A 257-amino acid internal region of the yeast open reading frame aligns with and shows 36% identity and 60% similarity to the rat liver stearoyl-CoA desaturase protein. This comparison disclosed three short regions of high consecutive amino acid identity (greater than 70%) including one 11 of 12 perfect residue match. The predicted yeast enzyme contains at least four potential membrane-spanning regions and several shorter hydrophobic regions that align exactly with similar sequences in the rat liver protein. An ole1 gene-disrupted yeast strain was transformed with a yeast-rat chimeric gene consisting of the promoter region and N-terminal 27 codons of OLE1 fused to the rat desaturase coding sequence. Fusion gene transformants displayed near equivalent growth rates and modest lipid composition changes relative to wild type yeast control implying a significant conservation of delta 9 desaturase tertiary structure and efficient interaction between the rat desaturase and yeast cytochrome b5. 相似文献
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Thomas C Meyer D Wolff M Himber C Alioua M Steinmetz A 《Plant molecular biology》2003,52(5):1025-1036
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M. Presler A. Wojtczyk-Miaskowska B. Schlichtholz A. Kaluzny M. Matuszewski A. Mika T. Sledzinski J. Swierczynski 《Molecular and cellular biochemistry》2018,447(1-2):217-224
Bladder cancer is a common disease and a significant cause of death worldwide. There is thus great interest in identifying a diagnostic and prognostic biomarker, as well as gaining an understanding of the molecular basis of bladder cancer. Stearoyl-CoA desaturase 1 gene (SCD1) is highly overexpressed in many human cancers. However, the expression of SCD1 has not yet been investigated in patients with bladder cancer. Here, we document that (a) the SCD1 is highly overexpressed in human bladder cancer; (b) high expression of SCD1 is more frequently observed in the late stage of disease and patients with lymph node metastasis; (c) bladder cancer patients with a higher SCD1 mRNA level have a poorer survival rate than those with normal SCD1 expression. Overall, this is the first report to indicate an association between SCD1 mRNA level and clinical indicators of human bladder cancer. Our study has provided evidence supporting the potential role of SCD1 as a biomarker for human bladder cancer prognosis. 相似文献
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Changes in the steady-state mRNA levels of the gene encoding cytochrome c were analyzed after feeding carbohydrates to detached leaves of sunflower (Helianthus annuus L.). Glucose, fructose and sucrose promoted an increase in mRNA levels, which was not observed with mannitol and other metabolites
such as glycerol or acetate. The increase in mRNA levels was proportionally higher in dark-treated leaves. The effect of sugars
could be mimicked by compounds that are phosphorylated by hexokinase but not further metabolized, such as mannose or 2-deoxyglucose.
This may indicate that hexokinase is involved in the induction of the cytochrome c gene by carbohydrates. The presence of potassium phosphate had no significant effect on the induction by sugars. Our results
indicate that the modulation of the expression of nuclear genes encoding mitochondrial components should be added to the list
of known effects of carbohydrates on respiration.
Received: 5 February 1998 / Accepted: 22 April 1998 相似文献
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We characterized a mutant T -cell lymphoma line selected for the inability to express the Thy-1 glycoprotein. This cell line is a member of the D complementation class of Thy-1– somatic cell mutants, and it lacks detectable cell-surface Thy-1.1 glycoprotein and detectable cytoplasmic Thy-1 mRNA. Southern blot analysis using a number of probes isolated from the clonedThy-1.2 gene demonstrated that, in the mutant, one copy of theThy-1 gene is absent from the genome and the other has undergone rearrangement. This rearrangement results from a deletion of the 5 portion of the gene removing the first two alternate exons and promoters and a portion of the second intron. The deletion breakpoint within the mutantThy-1 gene was localized to within 400 nucleotides by Southern blot analysis. The breakpoint is near two classes of mouse repetitive elements-a mouse B1-family repetitive element and a simple repetitive sequence-suggesting a mechanism of rearrangement leading to the mutation. Southern blot analysis demonstrated that two closely linked molecular markers on chromosome 9 are unaltered, demonstrating that the deletion in this mutant cell line is subchromosomal. 相似文献
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The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have
been assigned the accession number L50534 相似文献
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Classical sunflower varieties display a high linoleic acid content in their seeds [low oleic (LO) varieties] whereas genotypes
carrying the Pervenets mutation display an increased oleic acid content of above 83% [high oleic (HO) varieties]. Despite
the advantage in health terms of oleic acid, the nature of the mutation was still unknown. Previous work reported that HO
genotypes carried a specific oleate desaturase (OD) allele. This enzyme catalyses the desaturation of oleic acid into linoleic
acid. The present work demonstrates that this allele is organised in two parts: the first section present in both HO and LO
genotypes carries a normal OD gene, the second section is specific to HO genotypes and carries OD duplications. The study
of mRNA accumulation in LO and HO seeds revealed that the mutation is dominant and induces an OD mRNA down-regulation. Furthermore,
OD small interfering RNA, characteristic of gene silencing, accumulated specifically in HO seeds. Considered together, these
observations show that the mutation is associated with OD duplications leading to gene silencing of the OD gene and consequently,
to oleic acid accumulation. This finding allowed the development of molecular markers characterising the mutation that can
be used in breeding programmes to facilitate the selection of HO genotypes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献