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71.
The cellobiose catabolic system of Escherichia coli K12 is being used to
study the role of cryptic genes in evolution of new functions. Escherichia
coli does not use beta-glucoside sugars; however, mutations in several loci
can activate the cryptic bgl operon and permit growth on the beta-glucoside
sugars arbutin and salicin. Such Bgl+ mutants do not use cellobiose, which
is the most common beta-glucoside in nature. We have isolated a Cel+
(cellobiose-utilizing) mutant from a Bgl+ mutant of E. coli K12. The Cel+
mutant grows well on cellobiose, arbutin, and salicin. Genes for
utilization of these beta-glucosides are located at 37.8 min on the E. coli
map. The genes of the bgl operon are not involved in cellobiose
utilization. Introduction of a deletion covering bgl does not affect the
ability to utilize cellobiose, arbutin, or salicin, indicating that the new
Cel+ genes provide all three functions. Spontaneous cellobiose negative
mutants also become arbutin and salicin negative. Analysis of
beta-glucoside positive revertants of these mutants indicates that there
are separate loci for utilization of each of the beta-glucoside sugars. The
genes are closely linked and may be activated from a single locus. A fourth
gene at an unknown location increases the growth rate on cellobiose. The
cel genes constitute a second cryptic system for beta-glucoside utilization
in E. coli K12.
相似文献
72.
Cloning and characterization of the WAX2 gene of Arabidopsis involved in cuticle membrane and wax production 总被引:16,自引:0,他引:16 下载免费PDF全文
Insertional mutagenesis of Arabidopsis ecotype C24 was used to identify a novel mutant, designated wax2, that had alterations in both cuticle membrane and cuticular waxes. Arabidopsis mutants with altered cuticle membrane have not been reported previously. Compared with the wild type, the cuticle membrane of wax2 stems weighed 20.2% less, and when viewed using electron microscopy, it was 36.4% thicker, less opaque, and structurally disorganized. The total wax amount on wax2 leaves and stems was reduced by >78% and showed proportional deficiencies in the aldehydes, alkanes, secondary alcohols, and ketones, with increased acids, primary alcohols, and esters. Besides altered cuticle membranes, wax2 displayed postgenital fusion between aerial organs (especially in flower buds), reduced fertility under low humidity, increased epidermal permeability, and a reduction in stomatal index on adaxial and abaxial leaf surfaces. Thus, wax2 reveals a potential role for the cuticle as a suppressor of postgenital fusion and epidermal diffusion and as a mediator of both fertility and the development of epidermal architecture (via effects on stomatal index). The cloned WAX2 gene (verified by three independent allelic insertion mutants with identical phenotypes) codes for a predicted 632-amino acid integral membrane protein with a molecular mass of 72.3 kD and a theoretical pI of 8.78. WAX2 has six transmembrane domains, a His-rich diiron binding region at the N-terminal region, and a large soluble C-terminal domain. The N-terminal portion of WAX2 is homologous with members of the sterol desaturase family, whereas the C terminus of WAX2 is most similar to members of the short-chain dehydrogenase/reductase family. WAX2 has 32% identity to CER1, a protein required for wax production but not for cuticle membrane production. Based on these analyses, we predict that WAX2 has a metabolic function associated with both cuticle membrane and wax synthesis. These studies provide new insight into the genetics and biochemistry of plant cuticle production and elucidate new associations between the cuticle and diverse aspects of plant development. 相似文献
73.
Steven E Reid Emily J Kay Lisa J Neilson Anne‐Theres Henze Jens Serneels Ewan J McGhee Sandeep Dhayade Colin Nixon John BG Mackey Alice Santi Karthic Swaminathan Dimitris Athineos Vasileios Papalazarou Francesca Patella Álvaro Román‐Fernández Yasmin ElMaghloob Juan Ramon Hernandez‐Fernaud Ralf H Adams Shehab Ismail David M Bryant Manuel Salmeron‐Sanchez Laura M Machesky Leo M Carlin Karen Blyth Massimiliano Mazzone Sara Zanivan 《The EMBO journal》2017,36(16):2373-2389
Tumor progression alters the composition and physical properties of the extracellular matrix. Particularly, increased matrix stiffness has profound effects on tumor growth and metastasis. While endothelial cells are key players in cancer progression, the influence of tumor stiffness on the endothelium and the impact on metastasis is unknown. Through quantitative mass spectrometry, we find that the matricellular protein CCN1/CYR61 is highly regulated by stiffness in endothelial cells. We show that stiffness‐induced CCN1 activates β‐catenin nuclear translocation and signaling and that this contributes to upregulate N‐cadherin levels on the surface of the endothelium, in vitro. This facilitates N‐cadherin‐dependent cancer cell–endothelium interaction. Using intravital imaging, we show that knockout of Ccn1 in endothelial cells inhibits melanoma cancer cell binding to the blood vessels, a critical step in cancer cell transit through the vasculature to metastasize. Targeting stiffness‐induced changes in the vasculature, such as CCN1, is therefore a potential yet unappreciated mechanism to impair metastasis. 相似文献
74.
75.
Kyle R. Jenks Marcella M. Lucas Ben A. Duffy Ashlee A. Robbins Barjor Gimi Jeremy M. Barry Rod C. Scott 《PloS one》2013,8(12)
Children with malformations of cortical development (MCD) frequently have associated cognitive impairments which reduce quality of life. We hypothesized that cognitive deficits associated with MCD can be improved with environmental manipulation or additional training. The E17 methylazoxymethanol acetate (MAM) exposure model bears many anatomical hallmarks seen in human MCDs as well as similar behavioral and cognitive deficits. We divided control and MAM exposed Sprague-Dawley rats into enriched and non-enriched groups and tested performance in the Morris water maze. Another group similarly divided underwent sociability testing and also underwent Magnetic Resonance Imaging (MRI) scans pre and post enrichment. A third group of control and MAM rats without enrichment were trained until they reached criterion on the place avoidance task. MAM rats had impaired performance on spatial tasks and enrichment improved performance of both control and MAM animals. Although MAM rats did not have a deficit in sociability they showed similar improvement with enrichment as controls. MRI revealed a whole brain volume decrease with MAM exposure, and an increase in both MAM and control enriched volumes in comparison to non-enriched animals. In the place avoidance task, MAM rats required approximately 3 times as long to reach criterion as control animals, but with additional training were able to reach control performance. Environmental manipulation and additional training can improve cognition in a rodent MCD model. We therefore suggest that patients with MCD may benefit from appropriate alterations in educational strategies, social interaction and environment. These factors should be considered in therapeutic strategies. 相似文献
76.
77.
Eicosapentaenoic and docosahexaenoic acids production by and okara-utilizing potential of thraustochytrids 总被引:3,自引:0,他引:3
K W Fan F Chen E BG Jones L LP Vrijmoed 《Journal of industrial microbiology & biotechnology》2001,27(4):199-202
Nine thraustochytrid strains isolated from subtropical mangroves were screened for their eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA) production potential in a glucose yeast extract medium. Their ability to utilize okara (soymilk residue) for growth
and EPA and DHA production was also evaluated. EPA yield was low in most strains, while DHA level was high on glucose yeast
extract medium, producing 28.1–41.1% of total fatty acids, for all strains, with the exception of Ulkenia sp. KF13. The DHA yield of Schizochytrium mangrovei strains ranged from 747.7 to 2778.9 mg/l after 52 h of fermentation at 25°C. All strains utilized okara as a substrate for
growth, but DHA yield was lower when compared with fermentation in a glucose yeast extract medium. Journal of Industrial Microbiology & Biotechnology (2001) 27, 199–202.
Received 11 December 2000/ Accepted in revised form 29 June 2001 相似文献
78.
The intermediate lobe of the pituitary gland synthesizes a glycoprotein, proopiomelanocortin (POMC), which is cleaved by specific proteolytic enzymes to generate several hormonal peptides. The purpose of the present study was to examine the possible role of the carbohydrate moiety in the synthesis, intracellular processing and release of POMC-derived peptides in frog (Rana ridibunda) intermediate lobe cells. In vitro incorporation of [3H]-labelled glucosamine gave rise to three major radioactive products. Trypsin digestion of each of these glycopeptides gave a single glucosamine-labelled tryptic fragment with identical chromatographic characteristics. We conclude that Rana POMC is glycosylated in only one site (its gamma-MSH region) and that intracellular processing of this prohormone gives rise to smaller glycopeptides including glycosylated gamma-MSH. Treatment with the antibiotic tunicamycin (10 micrograms/ml, 6 hr) inhibited the glycosylation of POMC but did not significantly alter the neosynthesis of the peptide moiety of the precursor. Pulse-chase experiments combined with high-performance liquid chromatography analysis of the peptides derived from POMC revealed that inhibition of glycosylation by tunicamycin had no effect on the enzymatic cleavage of the precursor nor on the release of mature peptides. Thus, it is concluded that, in the frog, glycosylation of POMC has no influence on the biosynthesis, processing and release of intermediate lobe hormones. 相似文献
79.
Increased understanding of the influence of habitat (e.g., composition, patch size) and intrinsic (e.g., age, birth mass) factors on survival of neonatal pronghorn (Antilocapra americana) is a prerequisite to successful management programs, particularly as they relate to population dynamics and the role of population models in adaptive species management. Nevertheless, few studies have presented empirical data quantifying the influence of habitat variables on survival of neonatal pronghorn. During 2002–2005, we captured and radiocollared 116 neonates across two sites in western South Dakota. We documented 31 deaths during our study, of which coyote (Canis latrans) predation (n = 15) was the leading cause of mortality. We used known fate analysis in Program MARK to investigate the influence of intrinsic and habitat variables on neonatal survival. We generated a priori models that we grouped into habitat and intrinsic effects. The highest-ranking model indicated that neonate mortality was best explained by site, percent grassland, and open water habitat; 90-day survival (0.80; 90% CI = 0.71–0.88) declined 23% when grassland and water increased from 80.1 to 92.3% and 0.36 to 0.40%, respectively, across 50% natal home ranges. Further, our results indicated that grassland patch size and shrub density were important predictors of neonate survival; neonate survival declined 17% when shrub density declined from 5.0 to 2.5 patches per 100 ha. Excluding the site covariates, intrinsic factors (i.e., sex, age, birth mass, year, parturition date) were not important predictors of survival of neonatal pronghorns. Further, neonatal survival may depend on available land cover and interspersion of habitats. We have demonstrated that maintaining minimum and maximum thresholds for habitat factors (e.g., percentages of grassland and open water patches, density of shrub patches) throughout natal home ranges will in turn, ensure relatively high (>0.50) neonatal survival rates, especially as they relate to coyote predation. Thus, landscape level variables (particularly percentages of open water, grassland habitats, and shrub density) should be incorporated into the development or implementation of pronghorn management plans across sagebrush steppe communities of the western Dakotas, and potentially elsewhere within the geographic range of pronghorn. 相似文献
80.
Salvia subgenus Calosphace (Lamiaceae) is economically and ethnomedicinally significant and comprised of more than 500 species. Although strongly supported as monophyletic, it has received no comprehensive systematic research since the initial establishment of 91 taxonomic sections in 1939. Representative taxa of 73 sections of Calosphace were sampled to investigate the phylogenetic relationships and identify major lineages using chloroplast (intergenic spacer psbA-trnH) and nuclear ribosomal DNA (internal transcribed spacer). Phylogenetic analysis of the combined data sets established monophyly of seven sections (Blakea, Corrugatae, Erythrostachys, Hastatae, Incarnatae, Microsphace, and Sigmoideae) and four major lineages (S. axillaris, “Hastatae clade”, “Uliginosae clade”, and “core Calosphace”). Sections spanning two or more centers of diversity are not supported by our results; rather, supported relationships exhibit significant geographic structure. Mexico is supported as the geographic origin of Calosphace, and no more than seven dispersal events to South America are required to account for current disjunct distributions. 相似文献