ENC Value Research Articles

Codon usage bias of secretory protein in Fusarium oxysporum f. sp. cubense tropical race 4.

Banana Fusarium oxysporum f. sp. cubense tropical race 4 (Foc-TR4) is a highly destructive pathogen that infects nearly all major banana cultivars and has a tendency to spread further. Secreted proteins play a crucial role in the process of Fusarium wilt infection in bananas. In this study, we analyzed the codon usage bias (CUB) of the Foc-TR4 classical secretory protein genome for the first time and observed a strong bias toward codons ending with C. We found that 572 out of the 14,543 amino acid sequences in the Foc-TR4 genome exhibited characteristics of classical secretory proteins. The CUB was largely influenced by selection optimization pressure, as indicated by the ENC value and neutral plot analysis. Among the identified codons, such as UCC and CCC, 11 were found to be optimal for Foc-TR4 gene expression. Codons with higher GC content and a C base in the third position showed greater selectivity. The CUB in the secretory proteins encoded by Foc-TR4 provides insights into their evolutionary patterns, contributing to the development and screening of novel and effective antifungal drugs.

A detailed analysis of codon usages bias and influencing factors in the nucleocapsid gene of Nipah Virus

Several outbreaks of Nipah Virus (NiV) have recently been reported in various parts of the world including India. The 18.2-kb size single-stranded negative-sense RNA genome of NiV has six genes that encode nine proteins. Among nine, the nucleoprotein (N) protein is the most abundant viral protein. The relative availability of N protein is a determining factor for the activation of genome encapsidation, replicase activity, and regulating viral RNA synthesis. In this study, we have conducted a codon usage analysis of N protein-encoding gene (N gene) of NiV. The relative synonymous codon usage (RSCU) values, in combination with an ENC value of 51.048, represented low codon usage bias in the N gene. The effect of mutational pressure on codon usage bias was confirmed by significant correlations of GC3s, G3s, C3s, A3s, U3s, and ENC values with whole nucleotide contents (GC%, G%, C%, A%, and U%). Correlation study of GC3s, G3s, C3s, A3s, and U3s with axis values of correspondence analysis (CA) also supported the role of mutational pressure. The correlation study of Gravy values with GC3s, G3s, C3s, A3s, and U3s revealed the presence of natural selection in addition to mutational pressure on codon usage bias. Moreover, NiV codon adaptation index (CAI) value higher than their corresponding expected CAI (eCAI) values against human (CAI, 0.726; eCAI, 0.715), pig (CAI, 0.837; eCAI, 0.819), and bat (CAI, 0.762; eCAI, 0.750) also indicated natural selection play role on codon usage bias. Additionally, geographical distribution, and evolutionary processes also influenced the codon usage bias to some extent.

Comparative Analysis of Codon Usage Patterns in Chloroplast Genomes of Cherries

Synonymous codon usage bias (SCUB) analysis is an effective method to explore species specificity, evolutionary relationships and mRNA translation, as well as to discover novel genes, which are important for understanding gene function and molecular phylogeny. Cherries (Prunus subg. Cerasus) are flowering plant germplasm resources for edible and ornamental purposes. In this study, we analyzed the codon usage patterns of the 36 chloroplast genomes to provide a scientific basis for elucidating the evolution of subg. Cerasus. The results showed that the average GC content was 0.377, the average GC3 was 0.298, and the average ENC value was 49.69. Neutral-plot analysis, ENC-plot analysis, and PR2-plot analysis all indicated that natural selection was the main factor of codon usage bias in subg. Cerasus, whereas correlation analysis showed that gene expression level and GC1 also affect the codon usage pattern. The codon usage pattern was consistent across 36 species, and 30 high-frequency codons were identified, with preference for A/T endings; there were 23 optimal codons, and only GAU was identified in all individuals; structural differences existed between the clustering tree based on RSCU values and the phylogenetic tree based on CDS, elucidating the importance of locus mutations and no-preference codons in phylogenetic reconstruction. This study describes for the first time the SCUB pattern and characterization of subg. Cerasus chloroplast genomes and provides a new insight to explore the phylogeny of this subgenus.

Plastome structure, phylogenomics and evolution of plastid genes in Swertia (Gentianaceae) in the Qing-Tibetan Plateau

BackgroundThe genus Swertia is of great medicinal importance and one of the most taxonomically challenging taxa within Gentianaceae, largely due to the morphological similarities of species within this genus and with its closely related genera. Previous molecular studies confirmed its polyphyly but suffered from low phylogenetic resolutions because only limited sequence loci were used. Thus, we conducted the structural, gene evolutionary, and phylogenetic analyses of 11 newly obtained plastomes of Swertia. Our result greatly improved the phylogenetic resolutions in Swertia, shed new light on the plastome evolution and phylogenetic relationships of this genus.ResultsThe 11 Swertia plastomes together with the published seven species proved highly similar in overall size, structure, gene order, and content, but revealed some structural variations caused by the expansion and contraction of the IRb region into the LSC region, due to the heterogeneous length of the ψycf1. The gene rps16 was found to be in a state flux with pseudogenes or completely lost. Similar situation was also documented in other genera of Gentianaceae. This might imply loss of the gene in the common ancestor of Gentianaceae. The distribution plot of ENC vs. GC3 showed all these plastomes arranging very close in the Wright line with an expected ENC value (49–52%), suggesting the codon usage of Swertia was mainly constrained by a GC mutation bias. Most of the genes remained under the purifying selection, however, the cemA was identified under positive selection, possibly reflecting an adaptive response to low CO2 atmospheric conditions during the Late Miocene. Our phylogenomic analyses, based on 74 protein-coding genes (CDS), supported the polyphyly of Swertia with its close allies in the subtribe Swertiinae, presumably due to recent rapid radiation. The topology inferred from our phylogenetic analyses partly supported the current taxonomic treatment. Finally, several highly variable loci were identified, which can be used in future phylogenetic studies and accurate identification of medicinal genuineness of Swertia.ConclusionsOur study confirmed the polyphyly of Swertia and demonstrated the power of plastome phylogenomics in improvement of phylogenetic resolution, thus contributing to a better understanding of the evolutionary history of Swertia.

Influencing elements of codon usage bias in Birnaviridae and its evolutionary analysis

Birnaviridae is a family of double stranded (ds) RNA virus with non-enveloped virions and 2-segmented genomes. These viruses are known to cause diseases in many hosts. Virus of this family has affected the fish and poultry economy in a wide sector. Unevenness in the use of synonymous codons for a particular amino acid in the coding strand of DNA is known as codon usage bias (CUB). Codons that code the same amino acid are used with variable frequency in a variety of life forms. To understand the pattern of CUB in Birnaviridae, we carried out bioinformatics study to understand the properties of coding sequences of proteins. ENC value of Birnaviridae suggested low CUB. Nucleotide analysis revealed high GC content. Parameters such as RSCU values, nucleotide skewness, translational selection, parity plot and neutrality plot were studied to investigate the pattern of codon use and it was clear that both mutational pressure and natural selection contributed to the designing of CUB in Birnaviridae family. The neutrality plot revealed natural selection to dominate the structuring of CUB and hence remained the major CUB determinant in Birnaviridae. Outcome of our study exemplified the pattern of codon use in the Birnaviridae genomes and contributed the basic primary data for fundamental evolutionary research on them.

Analysis of Codon Usage of Speech Gene FoxP2 among Animals.

Simple SummaryWe evaluated codon usage bias in the FoxP2 gene in fishes, birds, reptiles, and mammals. Fishes use C or G—ending codons, while birds, reptiles, and mammals employ T or A—ending codons. Apart from the nucleotide composition, natural selection and mutation pressure might influence the CUB. The ENC observed/ENC expected ratio demonstrated that mutation pressure influences FoxP2 codon usage patterns. Natural selection may have had a key influence in shaping the CUB, although mutation pressure may have played a minor role. FoxP2 gene codon usage is affected by the base composition under mutation bias.The protein-coding gene FoxP2 (fork head box protein P2) plays a major role in communication and evolutionary changes. The present study carried out a comprehensive codon usage bias analysis in the FoxP2 gene among a diverse group of animals including fishes, birds, reptiles, and mammals. We observed that in the genome of fishes for the FoxP2 gene, codons ending with C or G were most frequently used, while in birds, reptiles, and mammals, codons ending with T or A were most frequently used. A higher ENC value was observed for the FoxP2 gene indicating a lower CUB. Parity role two-bias plots suggested that apart from mutation pressure, other factors such as natural selection might have influenced the CUB. The frequency distribution of the ENC observed and ENC expected ratio revealed that mutation pressure plays a key role in the patterns of codon usage of FoxP2. Besides, correspondence analysis exposed the composition of the nucleobase under mutation bias affects the codon usage of the FoxP2 gene. However, neutrality plots revealed the major role of natural selection over mutation pressure in the CUB of FoxP2. In addition, the codon usage patterns for FoxP2 among the selected genomes suggested that nature has favored nearly all the synonymous codons for encoding the corresponding amino acid. The uniform usage of 12 synonymous codons for FoxP2 was observed among the species of birds. The amino acid usage frequency for FoxP2 revealed that the amino acids Leucine, Glutamine, and Serine were predominant over other amino acids among all the species of fishes, birds, reptiles, and mammals.

Analysis of Codon Usage Bias in the chloroplast genome of Helianthus annuus J-01

In order to determine the usage of the codon against Helianthus annuus chloroplast genome, this study used Codon W 1.4.2 and online software CUSP to perform neutral mapping, ENC-plot and PR2-plot analysis on the coding sequence codes of 51 genes in the H. annuus J-01 chloroplast genome. The results showed the GC content of H. annuus J-01 chloroplast genome codons was GC1 (47.14%) > GC2 (39.44%) > GC3 (28.42%), indicating that the preference for synonymous codons in the chloroplast genome ends with A/U. The average ENC value is greater than 45, of which 37 are greater than 45. It shows that the H. annuus J-01 chloroplast genome has a weak bias. Through neutral plot analysis, ENC-plot analysis and PR2-plot analysis, it is found that the preference of H. annuus J-01 chloroplast genome codons is affected by selection as the main factor. The 12 optimal codons in the H. annuus J-01 chloroplast genome were finally determined: CUU, AUA, UAU, UAG, CAU, AAA, CCA, ACU, GCU, GAU, AGU, GGA.

Analysis of Codon Usage Bias in the <i>Platycarya</i> Chloroplast Genome

To detect the codon usage characteristics of chloroplast genomes in  Platycarya  genus, the CodonW 、 CUSP and SPSSAU software were employed to analyze the codon usage patterns of the chloroplast genomes protein-coding sequence in  Platycarya longipes  and  Platycarya strobilacea   in this research. Results show that the GC content of chloroplast genomes was 37.75% and 37.80%, the average GC content in the 3rd position was 27.16% and 27.25%. the range of effective codon number from 35.19 to 56.98, and there were more than 2/3 genes when ENC value greater than 45, which indicated a weak preference. According to the results of neutrality plot analysis, ENC-plot analysis and PR2-plot analysis, codon bias in most  Platycarya  chloroplast genes were affected by natural selection, while a few were affected by mutations or other factors. And based on the ENC value, five groups of high-expressed and low-expressed genes were identified, 16 codons were ended with A/U among the 18 optimal codons. The research has implications on codon optimization, enhancing the expression efficiency of exogenous gene and phylogenetic analysis.

Correlation between gene expression levels under drought stress and synonymous codon usage in rice plant by in-silico study.

We studied the correlation of synonymous codon usage (SCU) on gene expression levels under drought stress in rice. Sixty genes related to drought stress (with high, intermediate and low expression) were selected from rice meta-analysis data and various codon usage indices such as the effective number of codon usage (ENC), codon adaptation index (CAI) and relative synonymous codon usage (RSCU) were calculated. We found that in genes highly expressing under drought 1) GC content was higher, 2) ENC value was lower, 3) the preferred codons of some amino acids changed and 4) the RSCU ratio of GC-end codons relative to AT-end codons for 18 amino acids increased significantly compared with those in other genes. We introduce ARSCU as the Average ratio of RSCUs of GC-end codons to AT-end codons in each gene that could significantly separate high-expression genes under drought from low-expression genes. ARSCU is calculated using the program ARSCU-Calculator developed by our group to help predicting expression level of rice genes under drought. An index above ARSCU threshold is expected to indicate that the gene under study may belong to the “high expression group under drought”. This information may be applied for codon optimization of genes for rice genetic engineering. To validate these findings, we further used 60 other genes (randomly selected subset of 43233 genes studied for their response to drought stress). ARSCU value was able to predict the level of expression at 88.33% of the cases. Using third set of 60 genes selected amongst high expressing genes not related to drought, only 31.65% of the genes showed ARSCU value of higher than the set threshold. This indicates that the phenomenon we described in this report may be unique for drought related genes. To justify the observed correlation between CUB and high expressing genes under drought, possible role of tRNA post transcriptional modification and tRFs was hypothesized as possible underlying biological mechanism.

Comprehensive analysis of synonymous codon usage patterns in orf3 gene of porcine epidemic diarrhea virus in China

The ORF3 protein of porcine epidemic diarrhea virus (PEDV) is found to function as an ion channel which influences virus virulence and production. Taking consideration of the importance of PEDV orf3 gene, we have performed comprehensive analysis to investigate its synonymous codon usage patterns. In this study, the results of base composition analysis showed A/T rich and G/C poor in PEDV orf3 genes, and the most abundant base was nucleotide T. The relative synonymous codon usage value in each codon revealed that codon usage bias existed. The mean ENC value of each gene was 48.75, indicating a low codon usage bias, as well as a relatively instable change in PEDV orf3 genes. The general correlation analysis between base composition and codon usage bias indicated that mutational bias has an impact on the PEDV codon usage bias. Neutral analysis suggested that natural selection pressure takes a more important influence than mutational bias in shaping codon usage bias. Moreover, other factors including hydrophobicity and aromaticity have been also found to influence the codon usage variation among the PEDV orf3 genes. This study not only represents the most systematic analysis of codon usage patterns in PEDV orf3 genes, but also provides a basic shaping mechanism of the codon usage bias.

Exploring the codon patterns between CCD and NCED genes among different plant species

Plant carotenoid cleavage oxygenase (CCO) is an enzyme which catalyzes carotenoids to apocarotenoid products that are involved in several vital physiological functions. The CCO exists in two forms, namely, CCD (Carotenoid Cleavage Dioxygenase) and NCED (Nine-Cis Epoxycarotenoid Dioxygenase). This paper relates to a comparative study on CCD and NCED genes through phylogeny and codon usage analysis. The result of the phylogenetic analysis indicates a closer relationship between CCD and NCED subclass genes, while the RSCU values indicate a high preference for CUC codon in both CCD and NCED gene families. The mean ENc value of NCED genes was found to be 48.76, suggesting a higher codon bias compared to CCD genes. However, the ENc-GC3S plot suggests that both the gene families are under mutational pressure with variations according to their species-specific role. Similarly, the multivariate analysis also suggests that nucleotide mutation bias influences codon usage. Correlation analysis of Axis I and codon adaptation index values indicate a significant correlation between critical indices. Even though the prominence of the variations in codon usage between the two gene families, they are exerted towards the time-specific functional requirement for that plant species. This is evident from the cleaving roles of these enzymes against various carotenoids at different growth stages. The result of this investigation indicates that CCD and NCED genes are under mutational pressure. This codon bias study paves the way for increasing the production of apocarotenoids, which have a great significance in the industry.

Analysis of synonymous codon usage of chloroplast genome in Porphyra umbilicalis.

Synonymous codon usage bias is noticed in the genome of every organism, influenced by mutation pressure and natural selection. The analysis of codon usage pattern in Porphyra umbilicalis chloroplast genome are inferred while previous study focused on codon bias in nuclear genome. To develop a better understanding of the factors affecting synonymous codon usage, codon usage patterns and nucleotide composition of 150 genes in P. umbilicalis cp genome, and provide a theoretical basis for genetic modification of chloroplast genome. In this study, all codon usage bias parameters and nucleotide compositions were calculated by Python script, Codon W, DNA Star, CUSP of EMBOSS and Microsoft Excel. It shows that codon usage models are mainly influenced by compositional constraints under mutational pressure and synonymous codon prefers to use codons ending with A/T, comparing to C/G. The ENC value is slight low which shows the weak codon bias. For all coding genes of P. umbilicalis chloroplast genome except Photosystem I genes, a weak correlation between GC3 and GC12 suggests natural selection might play a significant role in synonymous codon usage bias. The codon usage bias in P. umbilicalis cp genome is low and in some way or other, influenced by natural selection, mutation pressure, nucleotide composition. Our results can provide a theoretical basis for codon modification of exogenous genes, accuracy of prediction about new members of chloroplast gene family and identification of unknown genome.

Analysis of Synonymous Codon Usage Bias in Flaviviridae Virus.

Background Flaviviridae viruses are single-stranded, positive-sense RNA viruses, which threat human constantly mediated by mosquitoes, ticks, and sandflies. Considering the recent increase in the prevalence of the family virus and its risk potential, we investigated the codon usage pattern to understand its evolutionary processes and provide some useful data to develop the medications for most of Flaviviridae viruses. Results The overall extent of codon usage bias in 65 Flaviviridae viruses is low with the average value of GC contents being 50.5% and the highest value being 55.9%; the lowest value is 40.2%. ENC values of Flaviviridae virus genes vary from 48.75 to 57.83 with a mean value of 55.56. U- and A-ended codons are preferred in the Flaviviridae virus. Correlation analysis shows that the positive correlation between ENC value and GC content at the third nucleotide positions was significant in this family virus. The result of analysis of ENC, neutrality plot analysis, and correlation analysis revealed that codon usage bias of all the viruses was affected mainly by natural selection. Meanwhile, according to correspondence analysis (CoA) based on RSCU and phylogenetic analysis, the Flaviviridae viruses mainly are made up of two groups, Group I (Yellow fever virus, Apoi virus, Tembusu virus, Dengue virus 1, and others) and Group II (West Nile virus lineage 2, Japanese encephalitis virus, Usutu virus, Kedougou virus, and others). Conclusions All in, the bias of codon usage pattern is affected not only by compositional constraints but also by natural selection. Phylogenetic analysis also illustrates that codon usage bias of virus can serve as an effective means of evolutionary classification in Flaviviridae virus.

Analysis of synonymous codon usage patterns of HPRT1 gene across twelve mammalian species

Genetic changes in Hypoxanthine guanine phosphoribosyltransferace (HPRT1) gene can alter the expression of the dopamine neurotransmitter leads to abnormal neuron function, a disease called Lesch-Nyhan syndrome (LNS). Although different studies were conducted on LNS, information on codon usage bias (CUB) of HPRT1 gene is limited. The present study examines the genetic determinants of CUB in HPRT1 gene using twelve mammalian species. In the coding sequence of HPRT1 genes, A/T ending codons was most frequently used. A higher ENC value was observed indicating lower HPRT1 gene expression in the selected mammalian species. Correlation analysis indicates that compositional constraints under mutation pressure can involve in CUB of HPRT1 genes among the selected mammalian species. Relative synonymous codon usage (RSCU) value revealed that the codons such as ACT, AGG, ATT and AGC were over-represented in each of the mammalian species. Result from the analysis of the RSCU indicates that compositional constraint is a key driver for the variation in codon usage. Ratio of nonsynonymous (dN) and synonymous (dS) substitution further suggested that purifying selection occurs among the HPRT1 gene of studied mammals to maintain its protein function under the process of evolution. Our findings report an insight into the codon usage patterns of HPRT1 gene and will be useful for LNS management.

Codon Pattern of Papillomavirus (Type I) from Bos Grunniens Based on the CodonW Software

Papillomavirus (Type I) from Bos Grunniens is a type of RNA virus. In order to understand the characteristics of codon usage and its main influencing factors, this study used CodonW software to carry out the preference analysis and multivariate statistical analysis of all the genes of Papillomavirus (Type I) from Bos Grunniens. The GC content, ENC value and RSCU value of all the three gene codons in each gene were examined. The results showed that the content of GC3 was relatively high. The ENC value is high too, indicating that the codon of the Papillomavirus (Type I) from Bos Grunniens is low in preference and prefers codons ending in bases G, C and A, which is different from the general preference of the Papillomavirus. Neutral plotting and ENC mapping analysis shows that codon preference is largely influenced by the selection effect. By comparing with the frequencies of other three kinds of biological codons, it is found that the frequency of codon usage differs from that of human. Based on this, optimal codons of Papillomavirus (Type I) were identified. The results for codon usages in Papillomavirus (Type I) are very good for developing genetic engineering vaccines and therapeutic antibodies.

Codon usage and expression level of human mitochondrial 13 protein coding genes across six continents

The study of codon usage coupled with phylogenetic analysis is an important tool to understand the genetic and evolutionary relationship of a gene. The 13 protein coding genes of human mitochondria are involved in electron transport chain for the generation of energy currency (ATP). However, no work has yet been reported on the codon usage of the mitochondrial protein coding genes across six continents. To understand the patterns of codon usage in mitochondrial genes across six different continents, we used bioinformatic analyses to analyze the protein coding genes. The codon usage bias was low as revealed from high ENC value. Correlation between codon usage and GC3 suggested that all the codons ending with G/C were positively correlated with GC3 but vice versa for A/T ending codons with the exception of ND4L and ND5 genes. Neutrality plot revealed that for the genes ATP6, COI, COIII, CYB, ND4 and ND4L, natural selection might have played a major role while mutation pressure might have played a dominant role in the codon usage bias of ATP8, COII, ND1, ND2, ND3, ND5 and ND6 genes. Phylogenetic analysis indicated that evolutionary relationships in each of 13 protein coding genes of human mitochondria were different across six continents and further suggested that geographical distance was an important factor for the origin and evolution of 13 protein coding genes of human mitochondria.

Codon usage bias and phylogenetic analysis of mitochondrial ND1 gene in pisces, aves, and mammals

The mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 1 (MT-ND1) gene is a subunit of the respiratory chain complex I and involved in the first step of the electron transport chain of oxidative phosphorylation (OXPHOS). To understand the pattern of compositional properties, codon usage and expression level of mitochondrial ND1 genes in pisces, aves, and mammals, we used bioinformatic approaches as no work was reported earlier. In this study, a perl script was used for calculating nucleotide contents and different codon usage bias parameters. The codon usage bias of MT-ND1 was low but the expression level was high as revealed from high ENC and CAI value. Correspondence analysis (COA) suggests that the pattern of codon usage for MT-ND1 gene is not same across species and that compositional constraint played an important role in codon usage pattern of this gene among pisces, aves, and mammals. From the regression equation of GC12 on GC3, it can be inferred that the natural selection might have played a dominant role while mutation pressure played a minor role in influencing the codon usage patterns. Further, ND1 gene has a discrepancy with cytochrome B (CYB) gene in preference of codons as evident from COA. The codon usage bias was low. It is influenced by nucleotide composition, natural selection, mutation pressure, length (number) of amino acids, and relative dinucleotide composition. This study helps in understanding the molecular biology, genetics, evolution of MT-ND1 gene, and also for designing a synthetic gene.

Prediction of gene expression and codon usage in human parasitic helminths

Codon usage bias refers to the differences in the occurrence frequency of synonymous codons. To understand the patterns of codon usage in mitochondrial genes we used bioinformatic approaches to analyze the protein coding sequences of W. bancrofti and S. haematobium as no work was reported earlier. It was found that the ENC value ranged from 43 to 60 with a mean of 46.91 in W. bancrofti but varied from 49 to 60 with a mean of 45.17 in S. haematobium, respectively. In W. bancrofti a significant positive correlation was found between ENC and GC3% (r = 0.826**, p < 0.01), but in S. haematobium significant correlation was found between ENC and GC3% (r = 0.983**, p < 0.01). Principal component analysis suggests that the pattern of codon usage significantly differed between W. bancrofti and S. haematobium. Neutrality plot reveals that natural selection played a major role while mutation pressure played a minor role in codon usage pattern in the mitochondrial protein coding genes of W. bancrofti and S. haematobium. Various factors namely nucleotide composition, natural selection and mutation pressure affected the codon usage pattern.

Codon Usage Bias in Two Hemipteran Insect Species:Bemisia tabaciandHomalodisca coagulata

Codon bias is the nonuniform use of synonymous codons which encode the same amino acid. Some codons are more frequently used than others in several organisms, particularly in the highly expressed genes. The spectacular diversity of insects makes them a suitable candidate for analyzing the codon usage bias. Recent expansion in genome sequencing of different insect species provides an opportunity for studying the codon usage bias. Several works on patterns of codon usage bias were done onDrosophilaand other related species but only few works were found in Hemiptera order. We analyzed codon usage in two Hemipteran insect species namelyBemisia tabaciandHomalodisca coagulata. Most frequent codons end with A or C at the 3rd codon position. The ENC (a measure of codon bias) value ranges from 43 to 60 (52.80) inB. tabacibut from 49 to 60 (56.69) inH. coagulata. In both insect species, a significant positive correlation was observed between A and A3%, C and C3%, and GC and GC3%, respectively. Our findings suggest that codon usage bias in two Hemipteran insect species is not remarkable and that mutation pressure causes the codon usage pattern in two Hemipteran insect species.

Characterization of the porcine epidemic diarrhea virus codon usage bias

Porcine epidemic diarrhea virus (PEDV) has been responsible for several recent outbreaks of porcine epidemic diarrhea (PED) and has caused great economic loss in the swine-raising industry. Considering the significance of PEDV, a systemic analysis was performed to study its codon usage patterns. The relative synonymous codon usage value of each codon revealed that codon usage bias exists and that PEDV tends to use codons that end in T. The mean ENC value of 47.91 indicates that the codon usage bias is low. However, we still wanted to identify the cause of this codon usage bias. A correlation analysis between the codon compositions (A3s, T3s, G3s, C3s, and GC3s), the ENC values, and the nucleotide contents (A%, T%, G%, C%, and GC%) indicated that mutational bias plays role in shaping the PEDV codon usage bias. This was further confirmed by a principal component analysis between the codon compositions and the axis values. Using the Gravy, Aroma, and CAI values, a role of natural selection in the PEDV codon usage pattern was also identified. Neutral analysis indicated that natural selection pressure plays a more important role than mutational bias in codon usage bias. Natural selection also plays an increasingly significant role during PEDV evolution. Additionally, gene function and geographic distribution also influence the codon usage bias to a degree.