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141.
We used a newly synthesized allotetraploid between C. sativus (2n = 2x = 14, n gametic chromosome number, x haploid chromosome number) and C. hystrix (2n = 2x = 24) to study the genomic events in its early generations. Results from cytological characterization of the F1 and the allotetraploid progenies showed that the rate of bivalents in meiotic metaphase I of the F1 was greatly improved by chromosome doubling, and further improved during the selfing process of allopolyploid resulting into
relatively diploid-like meiosis. Extensive genomic changes were detected by amplified fragment length polymorphism analysis.
The changes mainly involved loss of parental restriction fragments and gaining of novel fragments. The total detectable changes
were from 11.1 to 32.1%, and the frequency of losing parental fragments was much higher than that of gaining novel fragments.
Some of the changes were initiated as early as in the F1 hybrid, whereas others occurred after chromosome doubling (polyploid formation). No significant differences were detected
in the reciprocal F1 hybrids and S0 generations. But the data showed that the frequency of sequence losing in C. sativus was about two times higher than in the C. hystrix. Our results demonstrated that the sequence elimination was the major event of genomic changes, and it might provide the
physical basis for the diploid-like meiotic behavior in the diploidization of the newly formed allopolyploids. Moreover, the
results suggest that the sequence elimination was not caused by cytoplasmic factors, and might relate to genomic recombination
and to the numbers of parental chromosome. 相似文献
142.
Genome shuffling of <Emphasis Type="Italic">Streptomyces</Emphasis> sp. U121 for improved production of hydroxycitric acid 总被引:2,自引:0,他引:2
(2S, 3R)-Hydroxycitric acid (HCA) from Hibiscus subdariffa inhibits pancreatic α-amylase and intestine α-glucosidase, leading to reduction of carbohydrate metabolism. In our previous
study, Streptomyces sp. U121 was identified as a producer of (2S, 3R)-HCA [Hida et al. (2005) Bioscience, Biotechnology, and Biochemistry 69:1555–1561]. Here, we applied genome shuffling of Streptomyces sp. U121 to achieve rapid improvement of HCA production. The initial mutant population was generated by nitrosoguanidine
treatment of the spores, and an improved population producing fivefold more HCA over wild type was obtained by three rounds
of genome shuffling. For efficient screening of the mutant library, trans-epoxyaconitic acid (EAA), an antibiotic analog of HCA, was utilized. EAA inhibited the regeneration of nonfused protoplasts,
resulting in selective screening of shuffled strains. Mutant strains with enhanced EAA resistance exhibited significantly
higher HCA production in liquid media. Furthermore, the best mutant showed increased cell growth in flask culture, as well
as increased HCA production. 相似文献
143.
<Emphasis Type="Italic">Bacillus megaterium</Emphasis>—from simple soil bacterium to industrial protein production host 总被引:2,自引:0,他引:2
Vary PS Biedendieck R Fuerch T Meinhardt F Rohde M Deckwer WD Jahn D 《Applied microbiology and biotechnology》2007,76(5):957-967
Bacillus megaterium has been industrially employed for more than 50 years, as it possesses some very useful and unusual enzymes and a high capacity
for the production of exoenzymes. It is also a desirable cloning host for the production of intact proteins, as it does not
possess external alkaline proteases and can stably maintain a variety of plasmid vectors. Genetic tools for this species include
transducing phages and several hundred mutants covering the processes of biosynthesis, catabolism, division, sporulation,
germination, antibiotic resistance, and recombination. The seven plasmids of B. megaterium strain QM B1551 contain several unusual metabolic genes that may be useful in bioremediation. Recently, several recombinant
shuttle vectors carrying different strong inducible promoters and various combinations of affinity tags for simple protein
purification have been constructed. Leader sequences-mediated export of affinity-tagged proteins into the growth medium was
made possible. These plasmids are commercially available. For a broader application of B. megaterium in industry, sporulation and protease-deficient as well as UV-sensitive mutants were constructed. The genome sequence of
two different strains, plasmidless DSM319 and QM B1551 carrying seven natural plasmids, is now available. These sequences
allow for a systems biotechnology optimization of the production host B. megaterium. Altogether, a “toolbox” of hundreds of genetically characterized strains, genetic methods, vectors, hosts, and genomic sequences
make B. megaterium an ideal organism for industrial, environmental, and experimental applications. 相似文献
144.
Kunisawa T 《Antonie van Leeuwenhoek》2007,92(3):359-365
The availability of genomic sequence data allows new challenges to various biological problems. One of such attempts is the extraction of phylogenetic information from gene order data of genomes. Phylogenetic inferences are most commonly carried out on the basis of 16S rRNA trees, which sometimes produce unresolved or unreliable branching orders. One example for such a low resolution is recognized in the branching pattern among the phylum Actinobacteria. Here, gene arrangements characteristic of the Actinobacteria were identified, based on which Symbiobacterium thermophilum is phylogenetically placed outside that phylum, this being in contrast to 16S rRNA trees and to the current taxonomy in GenBank. Three transposition suggestive arrangements were found which support a notion that Rubrobacter xylanophilus is the earliest diverging species among the completely sequenced Actinobacteria. The gene arrangements identified here serve as a complement to previously reported indels and proteins characteristic of this phylum. 相似文献
145.
Disulfide reductases of host-colonising bacteria are involved in the expression of virulence factors, resistance to drugs,
and elimination of toxic compounds. Large-scale genome analyses of 281 prokaryotes identified CXXC and CXXC-derived motifs
in each microorganism. The total number of these motifs showed correlations with genome size and oxygen tolerance of the prokaryotes.
Specific bioinformatic analyses served to identify putative disulfide reductases in the Campylobacterales Campylobacter jejuni, Helicobacter pylori, Wolinella succinogenes and Arcobacter butzleri which colonise the gastrointestinal tract of higher animals. Three filters applied to the genomes of these species yielded
35, 25, 28 and 34 genes, respectively, encoding proteins with the characteristics of disulfide reductases. Ten proteins were
common to the four species, including four belonging to the thioredoxin system. The presence of thioredoxin reductase activities
was detected in the four bacterial species by observing dithiobis-2-nitrobenzoic acid reduction with β-nicotinamide adenine
dinucleotide phosphate as cofactor. Phylogenetic analyses of the thioredoxin reductases TrxB1 and TrxB2 of the four Campylobacterales were performed. Their TrxB1 proteins were more closely related to those of Firmicutes than to the corresponding proteins of other Proteobacteria. The
Campylobacterales TrxB2 proteins were closer to glutathione reductases of other organisms than to their respective TrxB1 proteins. The phylogenetic features of the Campylobacterales thioredoxin reductases suggested a special role for these enzymes
in the physiology of these bacteria.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
146.
Deciphering the mechanisms of intestinal imino (and amino) acid transport: The redemption of SLC36A1
The absorption of zwitterionic imino and amino acids, and related drugs, is an essential function of the small intestinal epithelium. This review focuses on the physiological roles of transporters recently identified at the molecular level, in particular SLC36A1, by identifying how they relate to the classical epithelial imino and amino acid transporters characterised in mammalian small intestine in the 1960s-1990s. SLC36A1 transports a number of d- and l-imino and amino acids, β- and γ-amino acids and orally-active neuromodulatory and antibacterial agents. SLC36A1 (or PAT1) functions as a proton-coupled imino and amino acid symporter in cooperation with the Na+/H+ exchanger NHE3 (SLC9A3) to produce the imino acid carrier identified in rat small intestine in the 1960s but subsequently ignored because of confusion with the IMINO transporter. However, it is the sodium/imino and amino acid cotransporter SLC6A20 which corresponds to the betaine carrier (identified in hamster, 1960s) and IMINO transporter (identified in rabbit and guinea pig, 1980s). This review summarises evidence for expression of SLC36A1 and SLC6A20 in human small intestine, highlights the differences in functional characteristics of the imino acid carrier and IMINO transporter, and explains the confusion surrounding these two distinct transport systems. 相似文献
147.
The minimum chromosome number of Glomus intraradices was assessed through cloning and sequencing of the highly divergent telomere-associated sequences (TAS) and by pulsed field gel electrophoresis (PFGE). The telomere of G. intraradices, as in other filamentous fungi, consists of TTAGGG repeats, this was confirmed using Bal31 nuclease time course reactions. Telomere length was estimated to be roughly 0.9 kb by Southern blots on genomic DNA and a telomere probe. We have identified six classes of cloned chromosomal termini based on the TAS. An unusually high genetic variation was observed within two of the six TAS classes. To further assess the total number of chromosome termini, we used telomere fingerprinting. Surprisingly, all hybridization patterns showed smears, which demonstrate that TAS are remarkably variable in the G. intraradices genome. These analyses predict the presence of at least three chromosomes in G. intraradices while PFGE showed a pattern of four bands ranging from 1.2 to 1.5 Mb. Taken together, our results indicate that there are at least four chromosomes in G. intraradices but there are probably more. The information on TAS and telomeres in the G. intradicies will be essential for making a physical map of the G. intraradices genome and could provide molecular markers for future studies of genetic variation among nuclei in these multigenomic fungi. 相似文献
148.
149.
Transposable elements are known to be “selfish DNA” sequences able to spread and be maintained in all genomes analyzed so far. Their evolution depends on the interaction they have with the other components of the genome, including genes and other transposable elements. These relationships are complex and have often been compared to those of species living and competing in an ecosystem. The aim of this current work is a proposition to fill the conceptual gap existing between genome biology and ecology, assuming that genomic components, such as transposable elements families, can be compared to species interacting in an ecosystem. Using this framework, some of the main models defined in the population genetics of transposable elements can then been reformulated, and some new kinds of realistic relationships, such as symbiosis between different genomic components, can then be modelled and explored. 相似文献
150.
During prepupal stage, the genes expression in silkgland is considered as a model for gene expression and regulation of eukaryotes. Aiming to comprehensively interpret gene expression profile in the silkgland, we collected all currently available EST, complete cDNA and protein expression information and other gene expression testing data published before, and explored their roles in their function pathways level. With the analysis of interaction between the known proteins and putative bio-macromolecules partners in silico, we list our prediction results in the form of pathway classification and test some of their expressions by experiments. 相似文献