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1.
Jungoh Ahn Min-Jung Jang Kok Siong Ang Hongweon Lee Eui-Sung Choi Dong-Yup Lee 《Biotechnology letters》2016,38(12):2137-2143
Objectives
To evaluate different codon optimization parameters on the Saccharomyces cerevisiae-derived mating factor α prepro-leader sequence (MFLS) to improve Candida antarctica lipase B (CAL-B) secretory production in Pichia pastoris.Results
Codon optimization based on the individual codon usage (ICU) and codon context (CC) design parameters enhanced secretory production of CAL-B to 7 U/ml and 12 U/ml, respectively. Only 3 U/ml was obtained with the wild type sequence while the sequence optimized using both ICU and CC objectives showed intermediate performance of 10 U/ml. These results clearly show that CC is the most relevant parameter for the codon optimization of MFLS in P. pastoris, and there is no synergistic effect achieved by considering both ICU and CC together.Conclusion
The CC optimized MFLS increased secretory protein production of CAL-B in P. pastoris by fourfold.2.
Background
Species of Paris Sect. Marmorata are valuable medicinal plants to synthesize steroidal saponins with effective pharmacological therapy. However, the wild resources of the species are threatened by plundering exploitation before the molecular genetics studies uncover the genomes and evolutionary significance. Thus, the availability of complete chloroplast genome sequences of Sect. Marmorata is necessary and crucial to the understanding the plastome evolution of this section and facilitating future population genetics studies. Here, we determined chloroplast genomes of Sect. Marmorata, and conducted the whole chloroplast genome comparison.Results
This study presented detailed sequences and structural variations of chloroplast genomes of Sect. Marmorata. Over 40 large repeats and approximately 130 simple sequence repeats as well as a group of genomic hotspots were detected. Inverted repeat contraction of this section was inferred via comparing the chloroplast genomes with the one of P. verticillata. Additionally, almost all the plastid protein coding genes were found to prefer ending with A/U. Mutation bias and selection pressure predominately shaped the codon bias of most genes. And most of the genes underwent purifying selection, whereas photosynthetic genes experienced a relatively relaxed purifying selection.Conclusions
Repeat sequences and hotspot regions can be scanned to detect the intraspecific and interspecific variability, and selected to infer the phylogenetic relationships of Sect. Marmorata and other species in subgenus Daiswa. Mutation and natural selection were the main forces to drive the codon bias pattern of most plastid protein coding genes. Therefore, this study enhances the understanding about evolution of Sect. Marmorata from the chloroplast genome, and provide genomic insights into genetic analyses of Sect. Marmorata.3.
Junhong Wei Jinjin Tian Guoqing Pan Jie Xie Jialing Bao Zeyang Zhou 《Biotechnology letters》2017,39(6):857-864
Objective
To develop a reliable and easy to use expression system for antibiotic production improvement of Streptomyces.Results
A two-compound T7 RNA polymerase-dependent gene expression system was developed to fulfill this demand. In this system, the T7 RNA polymerase coding sequence was optimized based on the codon usage of Streptomyces coelicolor. To evaluate the functionality of this system, we constructed an activator gene overexpression strain for enhancement of actinorhodin production. By overexpression of the positive regulator actII-ORF4 with this system, the maximum actinorhodin yield of engineered strain was 15-fold higher and the fermentation time was decreased by 48 h.Conclusion
The modified two-compound T7 expression system improves both antibiotic production and accelerates the fermentation process in Streptomyces. This provides a general and useful strategy for strain improvement of important antibiotic producing Streptomyces strains.4.
Weiyu Wang Jiaqi Sun Wenjun Xiao Li Jiang Ruyue Wang Jun Fan 《Biotechnology letters》2017,39(11):1733-1740
Objectives
To optimize the production of active inclusion bodies (IBs) containing human d-amino acid oxidase (hDAAO) in Escherichia coli.Results
The optimized initial codon region combined with the coexpressed rare tRNAs, fusion of each of the N-terminal partners including cellulose-binding module, thioredoxin, glutathione S-transferase and expressivity tag, deletion of the incorporated linker, and improvement of tRNA abundance affected the production and activity for oxidizing d-alanine of the hDAAO in IBs. Compared with the optimized fusion constructs and expression host, IBs yields and activity were increased to 2.6- and 2.8-fold respectively by changing the N-terminal codon bias of the hDAAO. The insoluble hDAAO codon variant displayed the same substrate specificity as the soluble one for oxidizing d-alanine, d-serine and d-aspartic acid. The freshly prepared hDAAO codon variant was used for analyzing the l-serine racemization activity of the bacterially expressed maize serine racemase.Conclusions
Optimization of the N-terminal codon bias combined with the coexpression of rare tRNAs is a novel and efficient approach to produce active IBs of the hDAAO.5.
Background
While the pathogenesis and epidemiology of tuberculosis are well studied, relatively little is known about the evolution of the infectious agent Mycobacterium tuberculosis, especially at the within-host level. The insertion sequence IS6110 is a genetic marker that is widely used to track the transmission of tuberculosis between individuals. This and other markers may also facilitate our understanding of the disease within patients.Results
This article presents three lines of evidence supporting the action of positive selection on M. tuberculosis within patients. The arguments are based on a comparison between empirical findings from molecular epidemiology, and population genetic models of evolution. Under the hypothesis of neutrality of genotypes, 1) the mutation rate of the marker IS6110 is unusually high, 2) the time it takes for substitutions to occur within patients is too short, and 3) the amount of polymorphism within patients is too low.Conclusions
Empirical observations are explained by the action of positive selection during infection, or alternatively by very low effective population sizes. I discuss the possible roles of antibiotic treatment, the host immune system and extrapulmonary dissemination in creating opportunities for positive selection.6.
Andrelisse Arruda Viviane Castelo Branco Reis Vinícius Daniel Ferreira Batista Bruno Sahim Daher Luiza Cesca Piva Janice Lisboa De Marco Lidia Maria Pepe de Moraes Fernando Araripe Gonçalves Torres 《Biotechnology letters》2016,38(3):509-517
Objectives
To develop a new vector for constitutive expression in Pichia pastoris based on the endogenous glycolytic PGK1 promoter.Results
P. pastoris plasmids bearing at least 415 bp of PGK1 promoter sequences can be used to drive plasmid integration by addition at this locus without affecting cell growth. Based on this result, a new P. pastoris integrative vector, pPICK2, was constructed bearing some features that facilitate protein production in this yeast: a ~620 bp PGK1 promoter fragment with three options of restriction sites for plasmid linearization prior to yeast transformation: a codon-optimized α-factor secretion signal, a new polylinker, and the kan marker for vector propagation in bacteria and selection of yeast transformants.Conclusions
A new constitutive vector for P. pastoris represents an alternative platform for recombinant protein production and metabolic engineering purposes.7.
Romel Gonzales-Salazar Bianca Cecere Michelina Ruocco Rosa Rao Giandomenico Corrado 《Biotechnology letters》2017,39(7):1049-1058
Objectives
To engineer broad spectrum resistance in potato using different expression strategies.Results
The previously identified Ribosome-Inactivating Protein from Phytolacca heterotepala was expressed in potato under a constitutive or a wound-inducible promoter. Leaves and tubers of the plants constitutively expressing the transgene were resistant to Botrytis cinerea and Rhizoctonia solani, respectively. The wound-inducible promoter was useful in driving the expression upon wounding and fungal damage, and conferred resistance to B. cinerea. The observed differences between the expression strategies are discussed considering the benefits and features offered by the two systems.Conclusions
Evidence is provided of the possible impact of promoter sequences to engineer BSR in plants, highlighting that the selection of a suitable expression strategy has to balance specific needs and target species.8.
9.
Objective
Concatenation of two NdeI–XhoI gene fragments via an oligonucleotide linker on a plasmid vector with an SfiI site was performed to evaluate success rates in construction of polycistronic genes expressible in Escherichia coli.Results
A series of plasmids with an SfiI site between the selection marker and the replication origin were constructed. The three wheat eEF1B subunit genes inserted between the NdeI and XhoI sites of pET-22b were transferred to the SfiI-containing plasmid with a spectinomycin-resistance gene. Then, the marker gene in the resultant plasmids was substituted with the ampicillin-resistance gene. These plasmids were used for concatenation of two different genes via a linker oligonucleotide containing a ribosome-binding site. During these operations, 42 clones were picked up out of which 41 had the intended product plasmid.Conclusion
This method, named as the SfiNX method, is useful for trial-and-error based testing of different combinations of fusion and co-expression partners for optimization of recombinant protein production.10.
Background
After coronary stenting, the risk of developing restenosis is from 20 to 35 %. The aim of the present study is to investigate the association of genetic variation in candidate genes in patients diagnosed with restenosis in the Kazakh population.Methods
Four hundred fifty-nine patients were recruited to the study; 91 patients were also diagnosed with diabetes and were excluded from the sampling. DNA was extracted with the salting-out method. The patients were genotyped for 53 single-nucleotide polymorphisms. Genotyping was performed on the QuantStudio 12K Flex (Life Technologies). Differences in distribution of BMI score among different genotype groups were compared by analysis of variance (ANOVA). Also, statistical analysis was performed using R and PLINK v.1.07. Haplotype frequencies and LD measures were estimated by using the software Haploview 4.2.Results
A logistic regression analysis found a significant difference in restenosis rates for different genotypes. FGB (rs1800790) is significantly associated with restenosis after stenting (OR?=?2.924, P?=?2.3E?06, additive model) in the Kazakh population. CD14 (rs2569190) showed a significant association in the additive (OR?=?0.08033, P?=?2.11E?09) and dominant models (OR?=?0.05359, P?=?4.15E?11). NOS3 (rs1799983) was also highly associated with development of restenosis after stenting in additive (OR?=?20.05, P?=?2.74 E?12) and recessive models (OR?=?22.24, P?=?6.811E?10).Conclusions
Our results indicate that FGB (rs1800790), CD14 (rs2569190), and NOS3 (rs1799983) SNPs could be genetic markers for development of restenosis in Kazakh population. Adjustment for potential confounder factor BMI gave almost the same results.11.
Objectives
To develop a versatile Trichoderma reesei (teleomorph Hypocrea jecorina) expression system for the high-purity production of heterologous proteins.Results
The versatile T. reesei expression system is based on xyn1 and xyn2 promoters, A824V transition in XYRI, and a bicomponent carbon source strategy. Red fluorescent protein gene rfp and alkaline endoglucanase EGV gene egv3 from Humicola insolens were used as reporter genes to test our versatile expression systemConclusions
The versatile T. reesei expression system can be applied to produce heterologous proteins with high purity and high yield.12.
Nicholas J. Bond Albert Koulman Julian L. Griffin Zoe Hall 《Metabolomics : Official journal of the Metabolomic Society》2017,13(11):128
Introduction
Mass spectrometry imaging (MSI) experiments result in complex multi-dimensional datasets, which require specialist data analysis tools.Objectives
We have developed massPix—an R package for analysing and interpreting data from MSI of lipids in tissue.Methods
massPix produces single ion images, performs multivariate statistics and provides putative lipid annotations based on accurate mass matching against generated lipid libraries.Results
Classification of tissue regions with high spectral similarly can be carried out by principal components analysis (PCA) or k-means clustering.Conclusion
massPix is an open-source tool for the analysis and statistical interpretation of MSI data, and is particularly useful for lipidomics applications.13.
Background
Evaluating the significance for a group of genes or proteins in a pathway or biological process for a disease could help researchers understand the mechanism of the disease. For example, identifying related pathways or gene functions for chromatin states of tumor-specific T cells will help determine whether T cells could reprogram or not, and further help design the cancer treatment strategy. Some existing p-value combination methods can be used in this scenario. However, these methods suffer from different disadvantages, and thus it is still challenging to design more powerful and robust statistical method.Results
The existing method of Group combined p-value (GCP) first partitions p-values to several groups using a set of several truncation points, but the method is often sensitive to these truncation points. Another method of adaptive rank truncated product method(ARTP) makes use of multiple truncation integers to adaptively combine the smallest p-values, but the method loses statistical power since it ignores the larger p-values. To tackle these problems, we propose a robust p-value combination method (rPCMP) by considering multiple partitions of p-values with different sets of truncation points. The proposed rPCMP statistic have a three-layer hierarchical structure. The inner-layer considers a statistic which combines p-values in a specified interval defined by two thresholds points, the intermediate-layer uses a GCP statistic which optimizes the statistic from the inner layer for a partition set of threshold points, and the outer-layer integrates the GCP statistic from multiple partitions of p-values. The empirical distribution of statistic under null distribution could be estimated by permutation procedure.Conclusions
Our proposed rPCMP method has been shown to be more robust and have higher statistical power. Simulation study shows that our method can effectively control the type I error rates and have higher statistical power than the existing methods. We finally apply our rPCMP method to an ATAC-seq dataset for discovering the related gene functions with chromatin states in mouse tumors T cell.14.
Background
We present a probabilistic topic-based model for content similarity called pmra that underlies the related article search feature in PubMed. Whether or not a document is about a particular topic is computed from term frequencies, modeled as Poisson distributions. Unlike previous probabilistic retrieval models, we do not attempt to estimate relevance–but rather our focus is "relatedness", the probability that a user would want to examine a particular document given known interest in another. We also describe a novel technique for estimating parameters that does not require human relevance judgments; instead, the process is based on the existence of MeSH ® in MEDLINE ®.Results
The pmra retrieval model was compared against bm25, a competitive probabilistic model that shares theoretical similarities. Experiments using the test collection from the TREC 2005 genomics track shows a small but statistically significant improvement of pmra over bm25 in terms of precision.Conclusion
Our experiments suggest that the pmra model provides an effective ranking algorithm for related article search.15.
Background
Lately, biomarker discovery has become one of the most significant research issues in the biomedical field. Owing to the presence of high-throughput technologies, genomic data, such as microarray data and RNA-seq, have become widely available. Many kinds of feature selection techniques have been applied to retrieve significant biomarkers from these kinds of data. However, they tend to be noisy with high-dimensional features and consist of a small number of samples; thus, conventional feature selection approaches might be problematic in terms of reproducibility.Results
In this article, we propose a stable feature selection method for high-dimensional datasets. We apply an ensemble L 1 -norm support vector machine to efficiently reduce irrelevant features, considering the stability of features. We define the stability score for each feature by aggregating the ensemble results, and utilize backward feature elimination on a purified feature set based on this score; therefore, it is possible to acquire an optimal set of features for performance without the need to set a specific threshold. The proposed methodology is evaluated by classifying the binary stage of renal clear cell carcinoma with RNA-seq data.Conclusion
A comparison with established algorithms, i.e., a fast correlation-based filter, random forest, and an ensemble version of an L 2 -norm support vector machine-based recursive feature elimination, enabled us to prove the superior performance of our method in terms of classification as well as stability in general. It is also shown that the proposed approach performs moderately on high-dimensional datasets consisting of a very large number of features and a smaller number of samples. The proposed approach is expected to be applicable to many other researches aimed at biomarker discovery.16.
17.
Wiltrud Erath Eva Bauer D. Brian Fowler Andres Gordillo Viktor Korzun Mira Ponomareva Malthe Schmidt Brigitta Schmiedchen Peer Wilde Chris-Carolin Schön 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2017,130(10):2151-2164
Key message
Rye genetic resources provide a valuable source of new alleles for the improvement of frost tolerance in rye breeding programs.Abstract
Frost tolerance is a must-have trait for winter cereal production in northern and continental cropping areas. Genetic resources should harbor promising alleles for the improvement of frost tolerance of winter rye elite lines. For frost tolerance breeding, the identification of quantitative trait loci (QTL) and the choice of optimum genome-based selection methods are essential. We identified genomic regions involved in frost tolerance of winter rye by QTL mapping in a biparental population derived from a highly frost tolerant selection from the Canadian cultivar Puma and the European elite line Lo157. Lines per se and their testcrosses were phenotyped in a controlled freeze test and in multi-location field trials in Russia and Canada. Three QTL on chromosomes 4R, 5R, and 7R were consistently detected across environments. The QTL on 5R is congruent with the genomic region harboring the Frost resistance locus 2 (Fr–2) in Triticeae. The Puma allele at the Fr–R2 locus was found to significantly increase frost tolerance. A comparison of predictive ability obtained from the QTL-based model with different whole-genome prediction models revealed that besides a few large, also small QTL effects contribute to the genomic variance of frost tolerance in rye. Genomic prediction models assigning a high weight to the Fr–R2 locus allow increasing the selection intensity for frost tolerance by genome-based pre-selection of promising candidates.18.
Vanessa Samúdio dos Santos Flávio Alves Macedo Jean Silva do Vale Denise Brentan Silva Carlos Alexandre Carollo 《Metabolomics : Official journal of the Metabolomic Society》2017,13(6):72
Background
Plant systematic studies have changed substantially in the last years, stimulated by new strategies for phylogenetic studies. In this regard, chemistry data has been a useful tool for understanding plant phylogenetic relationships.Objective
Our aim was to apply metabolomic approaches, followed by multivariate statistical analysis and dereplication of Tabebuia sensu lato species, and compare our results with classifications based on traditional taxonomy and molecular phylogeny. We also evaluated the application of metabolomics as a chemotaxonomic identification tool, as well as to enlighten plant chemical evolution.Methods
Metabolomic data was generated through a high-resolution mass spectrometry with electrospray ionization of 27 Tabebuia sensu lato specimens from different populations, consisting of 15 Handroanthus (from four species) and 12 Tabebuia sensu stricto (from three species). Chemometric tools, such as principal component analysis and metabolite heatmaps, were used to scrutinize the metabolic changes among species.Results
Tabebuia and Handroanthus species presented different secondary metabolite storage capacity. The genus Tabebuia revealed higher levels of glycosylated iridoids esterified with a phenylpropanoid moiety, such as specioside, verminoside, and minecoside, while Handroanthus accumulated iridoids linked to a simple phenol, lignans, and verbascoside derivatives.Conclusion
These results corroborate splitting the Tabebuia s.l., which was supported by profound changes in secondary metabolism, suggesting metabolomics as an excellent tool for understanding species evolution.19.
Thijs Welle Anna T. Hoekstra Ineke A. J. J. M. Daemen Celia R. Berkers Matheus O. Costa 《Metabolomics : Official journal of the Metabolomic Society》2017,13(7):83
Introduction
Swine dysentery caused by Brachyspira hyodysenteriae is a production limiting disease in pig farming. Currently antimicrobial therapy is the only treatment and control method available.Objective
The aim of this study was to characterize the metabolic response of porcine colon explants to infection by B. hyodysenteriae.Methods
Porcine colon explants exposed to B. hyodysenteriae were analyzed for histopathological, metabolic and pro-inflammatory gene expression changes.Results
Significant epithelial necrosis, increased levels of l-citrulline and IL-1α were observed on explants infected with B. hyodysenteriae.Conclusions
The spirochete induces necrosis in vitro likely through an inflammatory process mediated by IL-1α and NO.20.