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On the sample of 43 gamma-ray and neutron-induced inversion or translocation exchanges with the vestigial (vg) phenotype, the molecular cytogenetic analysis of distribution of exchange breakpoints on the molecular map of Drosophila vg region (subsection 49D3-4 on the polytene chromosome 2R) was performed using hybridisation in situ technique. Simultaneously, PCR-assay of DNA alterations in all exons and introns (except for intron 4) of the vg gene for 18 mutants with exchange breakpoints outside of the gene was carried out. The results obtained by these molecular genetic techniques have shown that 1) radiation-induced breaks under chromosome exchanges with the vg phenotype were regularly located inside of the vg gene (19 cases out of 43 studied ones or 44.2%) passing through the large introns; 2) breakpoints were frequently flanked by deletions of the gene as whole (3 exchanges) or of its major part (3 exchanges); 3) many of the breaks (18/43 or 41.8%) are situated outside (distal or proximal) of the gene although such mutants have got the vg phenotype; 4) 2/3 (12/18 or 66.7%) vg mutants with the breakpoint outside of gene show the intragenic DNA lesions (microdeletions, microinversions) occurring obviously independently and simultaneously with the neighbor chromosome breaks; 5) only each third vg mutant with break outside of the gene (6/18 or 33.3%) have the unchanged gene subregions under study and presents obviously the result of "position effect" which appear to manifest itself for a distance of 2-30 kb (more near and farther locations of the proximal and distal breakpoints, respectively, relative to the vg gene). Our findings showing regular induction of the multiple genetic lesions (chromosome breaks and mutations of the adjacent genes) on the both ends of chromosome exchange induced by single track produced by gamma-rays or neutrons were discussed as a scientific basis for the conceptually new approaches to the assessment of both genetic damage numbers in the cell genome with chromosome exchange (the multiple genetic lesions) and radiation genetic risk (our molecular genetic approach showing the need for an increase of risk levels at least on a factor of 3 for the heritable chromosome alterations detected by the ordinary cytogenetic monitoring).  相似文献   

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Xu X  Fang J  Wang W  Guo J  Chen P  Cheng J  Shen Z 《Transgenic research》2008,17(4):645-650
An alpha-amylase gene from Bacillus stearothermophilus under the control of the promoter of a major rice-seed storage protein was introduced into rice. The transgenic line with the highest alpha-amylase activity reached about 15,000 U/g of seeds (one unit is defined as the amount of enzyme that produces 1 mumol of reducing sugar in 1 min at 70 degrees C). The enzyme produced in the seeds had an optimum pH of 5.0-5.5 and optimum temperature of 60-70 degrees C. Without extraction or purification, the power of transgenic rice seeds was able to liquify 100 times its weight of corn powder in 2 h. Thus, the transgenic rice could be used for industrial starch liquefaction.  相似文献   

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In order to take advantage of the high thermostability of its product, β-1,3;1,4-glucanase (lichenase), we used a modified version of the licB gene from Clostridium thermocellum as a reporter gene for the analysis of gene expression in transformed plants. The coding region of the licB gene was truncated at both ends. The truncated enzyme retained its activity and thermostability. The modified gene (m-licB), with and without a plant leader peptide-encoding sequence, was expressed in tobacco plants under control of either the Agrobacterium octopine TR-DNA 2′ gene promoter or the promoter of the gene for the small subunit of ribulose-1,5-bisphosphate carboxylase. Expression of licB can be measured quantitatively and accurately, the assay is sensitive and simple enough to be used for analysis of various gene fusion systems or for screening of transformants. The enzyme is very stable and remains active in tissue extracts even after storage for 1 year and survives many thawing-freezing cycles. The lichenase-encoding gene was expressed at high levels in transformed tobacco plants without any apparent detrimental effects on vegetative growth or flowering. Received: 4 March 1997 / Accepted: 8 October 1997  相似文献   

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Virginiae butanolide (VB) is a member of the γ-butyrolactone autoregulators and triggers the production of streptogramin antibiotics virginiamycin M1 and S in Streptomyces virginiae. A VB biosynthetic gene (barS2) was localized in a 10-kb regulatory island which controls the virginiamycin biosynthesis/resistance of S. virginiae, and analyzed by gene disruption/complementation. The barS2 gene is flanked by barS1, another VB biosynthetic gene catalyzing stereospecific reduction of an A-factor-type precursor into a VB-type compound, and barX encoding a pleiotropic regulator for virginiamycin biosynthesis. The deduced product of barS2 possessed moderate similarity to a putative dehydrogenase of Streptomyces venezuelae, encoded by jadW 2 located in similar gene arrangement to that in the regulatory island of S. virginiae. A barS2-disruptant (strain IC152), created by means of homologous recombination, showed no differences in growth in liquid medium or morphology on solid medium compared to a wild-type strain, suggesting that BarS2 does not play any role in primary metabolism or morphological differentiation of S. virginiae. In contrast, no initiation of virginiamycin production or VB production was detected with the strain IC152 until 18 h of cultivation, at which time full production of virginiamycin occurs in the wild-type strain. The delayed virginiamycin production of the strain IC152 was fully restored to the level of the wild-type strain either by the exogenous addition of VB or by complementation of the intact barS2 gene, indicating that the lack of VB production at the initiation phase of virginiamycin production is the sole reason for the defect of virginiamycin production, and the barS2 gene is of primary importance for VB biosynthesis in S. virginiae. An erratum to this article can be found at  相似文献   

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Summary An allele giving rise to a polymorphism within the 3 part of the chicken vitellogenin gene was cloned, sequenced, and compared to the previously cloned allele. The polymorphism is formed by a perfect copy of 343 bp from intron 32 in tandem array with a perfect copy of 244 bp from intron 33; this 587-bp element is inserted in a head-to-tail arrangement in intron 33. We propose a mechanism in which an unequal crossing-over resulted in a vitellogenin gene with two exons 33, one of which was subsequently deleted. Thus, intron 33 was enlarged by the tandem repeats without affecting the protein-encoding sequence of the gene. At the boundaries of the repeated elements, two short direct repeats are found that resemble the recombination signals of immunoglobulin genes. They may have had a key role in the formation of the new allele.  相似文献   

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Genetic studies recently unraveled the genetic cause of sclerosteosis, a rare skeletal dysplasia characterized by a generalized increase in bone mass. Different loss-of-function mutations were identified in SOST, a gene with no homology to any known gene. This SOST gene is also involved in the pathogenesis of van Buchem disease, a disorder closely resembling sclerosteosis, since a 52-kb deletion located downstream of SOST is found in patients diagnosed with this condition. Molecular studies showed a very restricted expression pattern of SOST and its gene product, sclerostin, with areas in the bone tissue, more precisely in cells of the osteoblast lineage, being the major sites of expression. Sclerostin is a secreted protein with a cysteine knot motif. In vitro studies demonstrated that sclerostin acts as a modulator of BMP signaling by binding to different members of the BMP growth factor family and acting on downstream BMP signal transduction events. The important function of sclerostin in bone metabolism has also been proven in vivo by the osteopenic phenotype of transgenic mice overexpressing SOST in bone. The identification of sclerostin as an important protein in bone metabolism opens new perspectives for the development of anabolic therapeutics to prevent and treat osteoporosis.  相似文献   

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INTRODUCTIONPlantshavedevelopedseveralbi0chemicaldefensemechanismsinresp0nsetopath0gensandabioticstress.Fo1l0wingpathogenattack,plantsynthesizephenyl-propaniodpr0ductssuchaslignin,l0wm0l.wt.antimicrobia1comp0undsknownasphyt0alexins,andseveraldefense-relatedproteins.Amongthesepr0teinsare"pathogenesis-relatedproteins"includingthefungalcellwalldegradingenzymeschitinaseandP-1,3-glucanase[1].Endochitinasefromhigherplantscatalyzethehydr0lysis0fchitin,aP-1,4-linkedhomop0lymerofN-acetyl-D-glucos…  相似文献   

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Characterization of a divergent non-classical MHC class I gene in sharks   总被引:1,自引:0,他引:1  
Sharks are the most ancient group of vertebrates known to possess members of the major histocompatibility complex (MHC) gene family. For this reason, sharks provide a unique opportunity to gain insight into the evolution of the vertebrate immune system through comparative analysis. Two genes encoding proteins related to the MHC class I gene family were isolated from splenic cDNA derived from spiny dogfish shark ( Squalus acanthias). The genes have been designated MhcSqac-UAA*01 and MhcSqac-UAA*NC1. Comparative analysis demonstrates that the Sqac-UAA*01 protein sequence clusters with classical MHC class I of several shark species and has structural elements common to most classical MHC class I molecules. In contrast, Sqac-UAA*NC1 is highly divergent from all vertebrate classical MHC class I proteins, including the Sqac-UAA *01 sequence and those of other shark species. Although Sqac-UAA*NC1 is clearly related to the MHC class I gene family, no orthologous genes from other species were identified due to the high degree of sequence divergence. In fact, the Sqac NC1 protein sequence is the most divergent MHC class-I-like protein identified thus far in any shark species. This high degree of divergence is similar in magnitude to some of the MHC class-I-related genes found in mammals, such as MICA or CD1. These data support the existence of a class of highly divergent non-classical MHC class I genes in the most primitive vertebrates known to possess homologues of the MHC and other components of the adaptive immune system.  相似文献   

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Chitinase,which catalyzes the hydrolysis of the β-1,4-acetyl-D-glucosamine linkages of the fungal cell wall polymer chitin,is involved in inducible plants defense system.By construction of cabbage(Brassica oleracea var. capitata) genomic library and screening the library with pRCH8,a probe of rice chitinase gene fragment,a chitinase genomic sequence was isolated.The complete uncleotide sequence of the putative cabbage chitinase gene (cabch29) was determined,with its longest open reading frame (ORF) encoding a polypeptide of 413 aa.This polypeptide consists of a 21 aa N-terminal signal peptide,two chitin-binding domains different from those of other classes of plant chitinases,and a catalytic domain.Homology analysis illustrated that this cabch29 gene has 58.8% identity at the nucleotide level with the pRCH8 ORF probe and has 50% identity at the amino acid level tiwh the catalytic domains of chitinase from bean,maize and sugar beet.Meanwhile,several kinds of cis-elements,such as TATA box,CAAT box,GATA motif,ASF-1 binding site,wound-response elements and AATAAA,have also been discovered in the flanking region of cabch29 gene.  相似文献   

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Summary A -galactosidase gene from Lactobacillus sake coding for lactose hydrolysis was cloned and expressed in Escherichia coli. Chromosomal DNA from L. sake was partially digested with the restriction enzyme Sau3AI, and the 3–6 Kb fragment was ligated to the cloning vector pSP72 digested with BamHI. One E. coli transformant expressing -galactosidase was isolated on X-gal plates. It contained a plasmid with an insertion of approx. 4 Kb. The restriction map of the recombinant plasmid was constructed. The characteristics of the recombinant -galactosidase were compared with those of the wild type. The optima pH and temperature for both enzymes was 6.5 and 50°C, respectively. Stability of the enzymes at different temperatures and activity on lactose were determined.  相似文献   

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Summary Five genes of the -zein subfamily four (SF4) are located in a 56 kb genomic region of the maize inbred line W22. Their nucleotide and deduced amino acid sequences have been determined. The sequences define two types of -zein SF4 genes — type 1 (T1) and type 2 (T2). The single T1 -zein SF4 gene codes for an -zein protein with a Mr of about 22 000. This is the first -zein SF4 gene sequenced that contains no early in-frame stop codons in its coding sequence. The four T2 -zein SF4 genes in this cluster contain one or two early in-frame stop codons. In addition, our T1 and T2 genes differ markedly in the base sequences of their distal 5 non-translated flanking regions. The nucleotide and the deduced amino acid sequences of these two types of -zein SF4 genes are similar ( > 90 %) to one another and to all known -zein SF4 genes and cDNAs. Of the known W22 -zein SF4 genes, only one in six does not contain an early in-frame stop codon. If the number of -zein SF4 genes is 15–20, then we estimate that only about 4 of the W22 -zein SF4 genes are without in-frame early stop codons.  相似文献   

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Evolution of a Vκ gene family   总被引:2,自引:0,他引:2  
To examine the evolution of multigene families we have selected as an example an immunoglobulin light chain variable region subgroup (V24) which has been extensively characterized in inbred mice (Mus musculus domesticus). Homologous genes have been isolated and sequenced from Mus pahari, a genetically and geographically isolated species believed to be the oldest living representative of the genus. Southern blot analysis using probes corresponding to individual genes in this subgroup reveals changes in the overall size of the family occurring at the level of individual genes but not at the level of the entire family. Nucleotide sequence analysis indicates an absence of regulatory sequences such as the CAT and TATA boxes 5 to the coding region, but a decanucleotide sequence involved in light chain expression is highly conserved. Within coding regions highly complex patterns of variation are seen which appear to reflect quite different selective pressures on various subregions of the coding sequence. Complementarity determining regions (CDR) are conserved to different extents, with the first CDR region in all family members being among the most conserved segments of the molecule. Conservation is similarly variable among framework segments, indicating complex and variable evolutionary pressures not only at the level of individual genes or their products but also at subregions within homologous molecules.  相似文献   

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Green-revertible albino is a novel type of chlorophyll deficiency in rice (Oryza sativa L.), which is helpful for further research in chlorophyll synthesis and chloroplast development to illuminate their molecular mechanism. In the previous study, we had reported a single recessive gene, gra(t), controlling this trait on the long arm of chromosome 2. In this paper, we mapped the gra(t) gene using 1,936 recessive individuals with albino phenotype in the F2 population derived from the cross between themo-photoperiod-sensitive genic male-sterile (T/PGMS) line Pei'ai 64S and the spontaneous mutant Qiufeng M. Eventually, it was located to a confined region of 42.4 kb flanked by two microsatellite markers RM2-97 and RM13553. Based on the annotation results of RiceGAAS system, 11 open reading frames (ORFs) were predicted in this region. Among them, ORF6 was the most possible gene related to chloroplast development, which encoded the chloroplast protein synthesis elongation factor Tu in rice. Therefore, we designated it as the candidate gene of gra(t). Sequence analysis indicated that only one base substitution C to T occurred in the coding region, which caused a missense mutation (Thr to Ile) in gra(t) mutant. These results are very valuable for further study on gra(t) gene.  相似文献   

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Lolitrem B is synthesized by Epichlo? festucae in associations with Pooid grasses. A complex cluster of at least 10 genes (ltm genes) is required for its synthesis. An early step in this pathway is catalyzed by ltmM, a symbiosis-expressed gene. PltmM-gusA reporter gene analysis was used to monitor ltmM gene expression patterns in planta. The minimum promoter length required for high-level gusA expression in infected seedlings is in the range of 480 to 782 bp. gusA was expressed by the endophyte in all infected vegetative plant tissues and in epiphyllous hyphae. Spikelets from reproductive tillers were analyzed at different developmental stages. During pre-anthesis, gusA expression was observed in all infected floral organs except the immature gynoecium. In post-anthesis florets, gene expression occurred almost exclusively in the gynoecium. Expression of gusA by the endophyte was observed in germinating seeds 24 h postimbibition and seedlings older than 6 days postimbibition in hyphae from the mesocotyl to the tip of the emerging first leaf. This work provides a detailed analysis of the spatial and temporal expression patterns of a symbiosis-expressed gene in planta.  相似文献   

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