Similar Codon Usage Research Articles

Comparative analysis of codon usage patterns in 16 chloroplast genomes of suborder Halimedineae.

The Halimedineae are marine green macroalgae that play crucial roles as primary producers in various habitats, including coral reefs, rocky shores, embayments, lagoons, and seagrass beds. Several tropical species have calcified thalli, which contribute significantly to the formation of coral reefs. In this study, we investigated the codon usage patterns and the main factors influencing codon usage bias in 16 chloroplast genomes of the suborder Halimedineae. Nucleotide composition analysis revealed that the codons of these species were enriched in A/U bases and preferred to end in A/U bases, and the distribution of GC content followed a trend of GC1 > GC2 > GC3. 30 optimal codons encoding 17 amino acids were identified, and most of the optimal codons and all of the over-expressed codons preferentially ended with A/U. The neutrality plot, effective number of codons (ENc) plot, and parity rule 2 (PR2) plot analysis indicated that natural selection played a major role in shaping codon usage bias of the most Halimedineae species. The genetic relationships based on their RSCU values and chloroplast protein-coding genes showed the closely related species have similar codon usage patterns. This study describes, for the first time, the codon usage patterns and characterization of Halimedineae chloroplast genomes, and provides new insights into the evolution of this suborder.

Comparative analysis of mitochondrial genomes of invasive weed Mikania micrantha and its indigenous congener Mikania cordata

Mikania micrantha and Mikania cordata are two distinct species in China. The former is notorious as one of the top 100 worst invasive species, whereas the latter is an indigenous species harmless to native plants or the environment. They form an ideal congener pair for comparative studies aimed at deeply understanding the invasion mechanisms of the exotic weed. In this study, we have assembled and annotated the mitogenomes of both species using Illumina and PacBio sequencing data and compared their characteristic differences. The complete mitogenome of M. micrantha is a double-stranded DNA with a length of 336,564 bp, while the mitogenome of M. cordata exhibits a branching structure, consisting of two small circular molecules and six linear molecules, with a combined length totaling 335,444 bp. Compared to M. cordata, M. micrantha has less SSRs, tandem repeats, dispersed repeats, mitochondrial protein coding genes (PCGs). The two plants show similar codon usage patterns. This comparative study has revealed the structure and function of the mitogenomes of the two species and laid a solid foundation for investigating the effects of gene loss and duplication on the development of invasive traits in M. micrantha.

Codon Bias of the DDR1 Gene and Transcription Factor EHF in Multiple Species.

Milk production is an essential economic trait in cattle, and understanding the genetic regulation of this trait can enhance breeding strategies. The discoidin domain receptor 1 (DDR1) gene has been identified as a key candidate gene that influences milk production, and ETS homologous factor (EHF) is recognized as a critical transcription factor that regulates DDR1 expression. Codon usage bias, which affects gene expression and protein function, has not been fully explored in cattle. This study aims to examine the codon usage bias of DDR1 and EHF transcription factors to understand their roles in dairy production traits. Data from 24 species revealed that both DDR1 and EHF predominantly used G/C-ending codons, with the GC3 content averaging 75.49% for DDR1 and 61.72% for EHF. Synonymous codon usage analysis identified high-frequency codons for both DDR1 and EHF, with 17 codons common to both genes. Correlation analysis indicated a negative relationship between the effective number of codons and codon adaptation index for both DDR1 and EHF. Phylogenetic and clustering analyses revealed similar codon usage patterns among closely related species. These findings suggest that EHF plays a crucial role in regulating DDR1 expression, offering new insights into genetically regulating milk production in cattle.

Characterization and Phylogenetic Analysis of the Chloroplast Genomes of Stephania japonica var. timoriensis and Stephania japonica var. discolor.

This study sequenced the complete chloroplast genomes of Stephania japonica var. timoriensis and Stephania japonica var. discolor using the Illumina NovaSeq and PacBio RSII platforms. Following sequencing, the genomes were assembled, annotated, comparatively analyzed, and used to construct a phylogenetic tree to explore their phylogenetic positions. Results indicated that the chloroplast genomes of S. japonica var. timoriensis and S. japonica var. discolor both displayed a typical double-stranded circular tetrameric structure, measuring 157,609 and 157,748 bp in length, respectively. Each genome contained 130 annotated genes, with similar total GC content and relative codon usage patterns, showing a distinct preference for A/U at the third codon position. Simple sequence repeat analysis identified 207 and 211 repeats in S. japonica var. timoriensis and S. japonica var. discolor, respectively, primarily the A/T type. Boundary condition analysis indicated no significant expansion or contraction in the inverted repeat regions with consistent gene types and locations across both varieties. Nucleotide polymorphism analysis highlighted greater variation in the intergenic regions than in the coding sequences of Stephania chloroplast genomes. Phylogenetic analyses demonstrated that the species Stephania clustered into a distinct, well-supported clade. Notably, Stephania japonica, along with S. japonica var. discolor and S. japonica var. timoriensis, established a monophyletic lineage. Within this lineage, S. japonica and S. japonica var. discolor were closely related, with S. japonica var. timoriensis serving as their sister taxon.

Improved BioCyc Operon Prediction: Revisiting the Operon Prediction Problem.

Operon prediction is a valuable component of microbial-genome annotation because operon organization can yield inferences about gene function, and because knowledge of operon structure can aid the interpretation of gene expression data. We present a number of improvements to the existing Pathway Tools operon predictor based mostly on 7 new features that we hypothesized would increase its performance. The new features include shared Gene Ontology biological process terms, similarity of codon usage and GC content, correlated gene expression, and shared protein complex. We evaluated the proposed 7 new features and found that the addition of 6 of them improved the performance of the operon predictor from 79.55% to 83.49%, a decrease in error rate of 19.3%. When gene expression data was not included, the accuracy decreased to 82.547, still an improvement of 14.7%. One of the proposed features as well as a previously used feature had no effect and were removed. Although some of the new features had strong predictive value individually, when combined with the other features they did not have a large impact on predictive accuracy, suggesting that they were not independent from the other features.

Evidence for cross-species transmission of human coronavirus OC43 through bioinformatics and modeling infections in porcine intestinal organoids

Cross-species transmission of coronaviruses has been continuously posing a major challenge to public health. Pigs, as the major animal reservoirs for many zoonotic viruses, frequently mediate viral transmission to humans. This study comprehensively mapped the relationship between human and porcine coronaviruses through in-depth bioinformatics analysis. We found that human coronavirus OC43 and porcine coronavirus PHEV share a close phylogenetic relationship, evidenced by high genomic homology, similar codon usage patterns and comparable tertiary structure in spike proteins. Inoculation of infectious OC43 viruses in organoids derived from porcine small and large intestine demonstrated that porcine intestinal organoids (pIOs) are highly susceptible to human coronavirus OC43 infection and support infectious virus production. Using transmission electron microscopy, we visualized OC43 viral particles in both intracellular and extracellular compartments, and observed abnormalities of multiple organelles in infected organoid cells. Robust OC43 infections in pIOs result in a significant reduction of organoids viability and widespread cell death. This study bears essential implications for better understanding the evolutionary origin of human coronavirus OC43, and provides a proof-of-concept for using pIOs as a model to investigate cross-species transmission of human coronavirus.

Chloroplast genome analyses of Caragana arborescens and Caragana opulens

BackgroundNumerous species within the genus Caragana have high ecological and medicinal value. However, species identification based on morphological characteristics is quite complicated in the genus. To address this issue, we analyzed complete plastid genome data for the genus.ResultsWe obtained chloroplast genomes of two species, Caragana arborescens and Caragana opulens, using Illumina sequencing technology, with lengths of 129,473 bp and 132,815 bp, respectively. The absence of inverted repeat sequences in the two species indicated that they could be assigned to the inverted repeat-lacking clade (IRLC). The genomes included 111 distinct genes (4 rRNA genes, 31 tRNA genes, and 76 protein-coding genes). In addition, 16 genes containing introns were identified in the two genomes, the majority of which contained a single intron. Repeat analyses revealed 129 and 229 repeats in C. arborescens and C. opulens, respectively. C. arborescens and C. opulens genomes contained 277 and 265 simple sequence repeats, respectively. The two Caragana species exhibited similar codon usage patterns. rpl20-clpP, rps19-rpl2, and rpl23-ycf2 showed the highest nucleotide diversity (pi). In an analysis of sequence divergence, certain intergenic regions (matK-rbcL, psbM-petN, atpA-psbI, petA-psbL, psbE-petL, and rps7-rps12) were highly variable. A phylogenetic analysis showed that C. arborescens and C. opulens were related and clustered together with four other Caragana species. The genera Astragalus and Caragana were relatively closely related.ConclusionsThe present study provides valuable information about the chloroplast genomes of C. arborescens and C. opulens and lays a foundation for future phylogenetic research and molecular marker development.

Comparative mitochondrial genome brings insights to slight variation in gene proportion and large intergenic spacer and phylogenetic relationship of mudskipper species

Fish mitochondrial genome have been largely studied worldwide for evolutionary and other genetic purposes and the structure and gene organization are commonly conservative. However, several studies have demonstrated that this scenario may present variations in some taxa, showing differentiation on the gene rearrangement. In this study, the complete mitogenome of terrestrial fish Boleophthalmus dussumieri was generated and compared with other species of the Exudercidae fishes. The newly complete mitogenome generated is circular and 16,685 bp of length, and it contained 13 protein-coding genes (PCGs), two ribosomal RNA (rRNAs), 22 transfer RNA genes (tRNAs), and one control region (CR), with high conservative structure, like other Mudskippers. Most of the PCG showed similar codon usage bias. The gene length was found to be different specially for the CR, 12S rRNA gene and ND5 gene in some taxon. All the Boleophthalmus species showed a gene duplication in the CR, except for B. dussumieri, and they presented a long intergenic spacer specially on the tRNA-Pro/ OH Tandem duplication/random loss (TDRL) and dimer-mitogenome and nonrandom loss (DMNL) are suitable to explain the mitogenome rearrangement observed in this study. The phylogenetic analysis well supported the monophyly of all mudskipper species and the analysis positioned the Periophthalmus clade as the most basal of the terrestrial fishes. This finding provides basis and brings insights for gene variation, gene rearrangements and replications showing evidence for variety of mitochondrial structure diversity within mudskippers.

Mitogenomics, phylogeny and morphology reveal two new entomopathogenic species of Ophiocordyceps (Ophiocordycipitaceae, Hypocreales) from south-western China.

Ophiocordyceps encompasses over 300 species, demonstrating a wide range of morphological features, hosts and habitats within its species diversity. In this study, two novel species in Ophiocordyceps were revealed parasitising Hepialidae larva buried in soil. Ophiocordycepsalbastroma was morphologically characterised by white stromata, solitary and cylindrical conidiogenous cells and smooth ovoid or ellipsoidal conidia. Ophiocordycepsnigristroma was characterised by woody and dark brown stromata, monophialidic, swollen base and lageniform conidiogenous cells and smooth fusiform or oval conidia. The two new species formed a separate clade, respectively, based on the phylogenetic analyses of a combined dataset including nrSSU, nrLSU, rpb1, rpb2, and tef-1α, as well as a dataset of mitochondrial 14 protein coding genes (PCGs). They were all closely grouped with O.sinensis. The mitochondrial genomes of them were first reported. Their mitogenomes were all typical of circular molecules, with positive AT and GC skew, similar GC content, similar genetic composition, similar codon usage and conservative gene positions. However, the length of the mitogenomes varied. Changes in the length of the genes were the leading cause of changes in the length of mitochondrial genome of Ophiocordyceps. The discovery and identification of new Ophiocordyceps species and analysis their mitochondrial genomes may serve as foundations for phylogeny and diversity research within the genus Ophiocordyceps.

The complete chloroplast genome sequences of three Pedicularis species (Orobanchaceae).

Pedicularis L., a generally bothersome genus of hemiparasitic plants, is primarily native to southwestern China. The phylogenetic relationship and evolutionary history of this genus have not yet been fully resolved. In this study, we sequenced and assembled chloroplast genomes of three Pedicularis species, P. chinensis, P. melampyriflora, and P. striata using high-throughput Illumina sequencing. The assembled plastomes were 142,059 bp (P. chinensis) to 152,146 bp (P. striata) in size, containing 110 (P. chinensis) to 117 (P. striata) genes. Moreover, we identified 13-15 pseudogenes within the three plastomes, nine of which were pseudogenized in all three species. The three plastomes exhibited a similar codon usage pattern. Moreover, the plastomes contained abundant simple sequence repeats and long repeats, which showed slight variations between the three species. A maximum likelihood analysis was performed to elucidate the phylogenetic positions of the three species within the Pedicularis genus. The plastomes presented in our study can be used as valuable genomic resources for further genetic and genomic studies of the Pedicularis genus.

First mitochondrial genomes of the crane fly tribe Elephantomyiini (Diptera, Tipuloidea, Limoniidae): comparative analysis and phylogenetic implications

Limoniidae, the most speciose family in the superfamily Tipuloidea, consists of four subfamilies and more than 11,000 species. However, mitochondrial (mt) genome sequences, which have been widely used for phylogenetic study, are available for only 11 species across three subfamilies. Thus, a larger variety of mt genome sequences in Limoniidae are required to improve our understanding of tipuloid phylogeny and genomic evolution. Here we present mt genomes of Elephantomyia (Elephantomyia) inulta Alexander, 1938 and Helius (Helius) pluto Alexander, 1932, representing the first mt genomes of the tribe Elephantomyiini (Limoniidae). The two mt genomes are typical circular DNA molecules and show similar gene order, nucleotide composition and codon usage. Standard ATN start and TAR stop codons are present in most protein-coding genes. All transfer RNA (tRNA) genes exhibited the cloverleaf secondary structure typical for metazoans except in tRNASer(AGN), which lacks the dihydrouridine arm. Phylogenetic analyses were performed based on four nucleotide matrixes for the currently sequenced species of Tipuloidea using Bayesian inference and maximum likelihood methods. Four-cluster likelihood mapping was used to study incongruent signals between different topologies. Pediciidae is supported as the earliest lineage in Tipuloidea, and the sister-group relationship between Cylindrotomidae and Tipulidae is also supported, but the monophyly of Limoniidae is not supported. Our study also supports the monophyly of Elephantomyiini (Elephantomyia + Helius), as one of origins of flower-visiting in Limoniidae. Although Elephantomyiini is sister to Limoniinae + Epiphragma (Limnophilinae) in our study, a more precise understanding of its phylogenetic position in Tipuloidea will require additional studies that include a broader species sample.

Mutation and codon bias analysis of the spike protein of Omicron, the recent variant of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant is a heavily mutated virus and designated as a variant of concern. To investigate the codon usage pattern of this new variant, we performed mutation and codon bias analysis for Omicron as well as for its sub-lineages BA.1 and BA.2 and compared them with the original SARS-CoV-2 and the Delta variant sequences obtained in this study. Our results indicate that the sub-lineage BA.1 and BA.2 have up to 23 sites of difference on the spike protein, which have minimal impact on function. The Omicron variant and its sub-lineages have similar codon usage patterns and A/U ending codons appear to be preferred over G/C ending codons. The Omicron has a lower degree of codon usage bias in spite of evidence that natural selection, mutation pressure and dinucleotide abundance shape the codon usage bias of Omicron, with natural selection being more significant on BA.2 than the other sub-lineages of Omicron. The codon usage pattern of Omicron variant that we explored provides valid information for a clearer understanding of Omicron and its sub-lineages, which could find application in vaccine development and optimization.

Contribution to the Knowledge of Dicranoptychini (Diptera, Tipuloidea, Limoniidae) in China, with the First Mitochondrial Genome of the Tribe and Its Phylogenetic Implications.

Dicranoptychini is a tribe in the subfamily Limoniinae (Diptera, Tipuloidea, and Limoniidae) and includes only the genus Dicranoptycha Osten Sacken, 1860. However, the species diversity of the tribe in China was seriously underestimated, and the taxonomic status of Dicranoptycha has long been controversial. In this study, types of Chinese Dicranoptycha species and specimens collected from several localities in China were examined, and the first mitochondrial (mt) genome of the tribe Dicranoptychini is presented. Two Dicranoptycha species, D. jiufengshana sp. nov. and D. shandongensis sp. nov., from China, are described and illustrated as new to science. A Palaearctic species, D. prolongata Alexander, 1938, is recorded in China for the first time. In addition, the complete mt genome of D. shandongensis sp. nov. is sequenced and annotated, indicating that it is a typical circular DNA molecule with a length of 16,157 bp and shows a similar gene order, nucleotide composition, and codon usage to mt genomes of other Tipuloidea species. The two pairs of repeat elements are found in its control region. Phylogenetic results confirm the sister-group relationship between Cylindrotomidae and Tipulidae, question the position of the genus Epiphragma Osten Sacken, 1860 in Limoniidae, and indicate that Dicranoptychini may be a basal lineage within Limoniinae.

Structural Characteristics and Phylogenetic Analysis of the Mitochondrial Genomes of Four Krisna Species (Hemiptera: Cicadellidae: Iassinae).

Krisna species are insects that have piercing-sucking mouthparts and belong to the Krisnini tribe in the Iassinae subfamily of leafhoppers in the Cicadellidae family. In this study, we sequenced and compared the mitochondrial genomes (mitogenomes) of four Krisna species. The results showed that all four mitogenomes were composed of cyclic double-stranded molecules and contained 13 protein-coding genes (PCGs) and 22 and 2 genes coding for tRNAs and rRNAs, respectively. Those mitogenomes exhibited similar base composition, gene size, and codon usage patterns for the protein-coding genes. The analysis of the nonsynonymous substitution rate (Ka)/synonymous substitution rate (Ks) showed that evolution occurred the fastest in ND4 and the slowest in COI. 13 PCGs that underwent purification selection were suitable for studying phylogenetic relationships within Krisna. ND2, ND6, and ATP6 had highly variable nucleotide diversity, whereas COI and ND1 exhibited the lowest diversity. Genes or gene regions with high nucleotide diversity can provide potential marker candidates for population genetics and species delimitation in Krisna. Analyses of parity and neutral plots showed that both natural selection and mutation pressure affected the codon usage bias. In the phylogenetic analysis, all subfamilies were restored to a monophyletic group; the Krisnini tribe is monophyletic, and the Krisna genus is paraphyletic. Our study provides novel insights into the significance of the background nucleotide composition and codon usage patterns in the CDSs of the 13 mitochondrial PCGs of the Krisna genome, which could enable the identification of a different gene organization and may be used for accurate phylogenetic analysis of Krisna species.

Comparative Mitogenome Analyses Uncover Mitogenome Features and Phylogenetic Implications of the Parrotfishes (Perciformes: Scaridae).

In order to investigate the molecular evolution of mitogenomes among the family Scaridae, the complete mitogenome sequences of twelve parrotfish species were determined and compared with those of seven other parrotfish species. The comparative analysis revealed that the general features and organization of the mitogenome were similar among the 19 parrotfish species. The base composition was similar among the parrotfishes, with the exception of the genus Calotomus, which exhibited an unusual negative AT skew in the whole mitogenome. The PCGs showed similar codon usage, and all of them underwent a strong purifying selection. The gene rearrangement typical of the parrotfishes was detected, with the tRNAMet inserted between the tRNAIle and tRNAGln, and the tRNAGln was followed by a putative tRNAMet pseudogene. The parrotfish mitogenomes displayed conserved gene overlaps and secondary structure in most tRNA genes, while the non-coding intergenic spacers varied among species. Phylogenetic analysis based on the thirteen PCGs and two rRNAs strongly supported the hypothesis that the parrotfishes could be subdivided into two clades with distinct ecological adaptations. The early divergence of the sea grass and coral reef clades occurred in the late Oligocene, probably related to the expansion of sea grass habitat. Later diversification within the coral reef clade could be dated back to the Miocene, likely associated with the geomorphology alternation since the closing of the Tethys Ocean. This work provided fundamental molecular data that will be useful for species identification, conservation, and further studies on the evolution of parrotfishes.

The origin and evolution of emerged swine acute diarrhea syndrome coronavirus with zoonotic potential.

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a newly discovered alphacoronavirus with zoonotic potential that causes diarrhea and vomiting mainly in piglets. Having emerged suddenly in 2017, the prevailing opinion is that the virus originated from HKU2, an alphacoronavirus whose primary host is bats, and at some unknown point achieved interspecies transmission via some intermediate. Here, we further explore the evolutionary history and possible cross-species transmission event for SADS-CoV. Coevolutionary analysis demonstrated that HKU2 may have achieved host switch via SADS-related (SADSr)-CoV, which was isolated from the genus Rhinolophus in 2017. SADS-CoV, HKU2 and SADSr-CoV share similar codon usage patterns and showed a lower tendency to use CpG, which may reflect a method of immune escape. The analyses of virus-host coevolution and recombination support SADSr-CoV is the direct source of SADS-CoV that may have undergone recombination events during its formation. Structure-based spike glycoprotein variance analysis revealed a more nuanced evolutionary pathway to receptor recognition for host switch. We did not find a possible positive selection site, and the dN/dS of the S gene was only 0.29, which indicates that the current SADS-CoV is slowly evolving. These results provide new insights that may help predict future cross-species transmission, and possibly surveil future zoonotic outbreaks and associated public health emergencies. This article is protected by copyright. All rights reserved.

Comparative chloroplast genome and phylogenetic analyses of Chinese Polyspora.

Polyspora Sweet (Theaceae) are winter ornamental landscape plants native to southern and southeastern Asia, some of which have medicinal value. The chloroplast (cp) genome data of Polyspora are scarce, and the gene evolution and interspecific relationship are still unclear. In this study, we sequenced and annotated Polyspora chrysandra cp genome and combined it with previously published genomes for other Chinese Polyspora species. The results showed that cp genomes of six Chinese Polyspora varied in length between 156,452 bp (P. chrysandra) and 157,066 bp (P. speciosa), but all contained 132 genes, with GC content of 37.3%, and highly similar genes distribution and codon usage. A total of eleven intergenic spacer regions were found having the highest levels of divergence, and eight divergence hotspots were identified as molecular markers for Phylogeography and genetic diversity studies in Polyspora. Gene selection pressure suggested that five genes were subjected to positive selection. Phylogenetic relationships among Polyspora species based on the complete cp genomes were supported strongly, indicating that the cp genomes have the potential to be used as super barcodes for further analysis of the phylogeny of the entire genus. The cp genomes of Chinese Polyspora species will provide valuable information for species identification, molecular breeding and evolutionary analysis of genus Polyspora.

Analysis of codon usage patterns in Haloxylon ammodendron based on genomic and transcriptomic data

Haloxylon ammodendron, a xero-halophytic shrub of Chenopodiaceae, is a dominant species in deserts, which has a strong drought and salt tolerance and plays an important role in sand fixation. However, the codon usage bias (CUB) in H. ammodendron is still unclear at present. In this study, the codon usage patterns of 38,657 coding sequences (CDSs) in the newly released whole-genome sequence data of H. ammodendron and 3,948 CDSs in the previously obtained transcriptome sequencing data were compared and analyzed. The results showed that the CDSs with the total guanineandcytosine(GC)content in the range of 40–45 % was the most in the genome and transcriptome. Among which, the GC1, GC2, and GC3 contents of genomic CDSs were 50.83 %, 40.56 %, and 40.23 %, respectively, and those of CDSs in the transcriptome were 47.16 %, 39.02 %, and 39.59 %, respectively. Therefore, the bases in H. ammodendron were rich in adenine and thymine, and the overallcodonusage was biasedtoward A- and U-ending codons. The analysis of neutrality plot, effective number of codon (ENC) plot, and parity rule 2 (PR2) bias plot showed that both natural selection and mutation pressure had great influences on the CUB of H. ammodendron, but natural selection was the most important determinant. Besides, gene expression level and the function and protein length of some specific genes also had influences on the codon usage pattern. Finally, a total of 25 common optimal codons were found in the genomic and transcriptomic data, and AU/GC-ending codons ratio was 24:1. It should be noted that the salt-tolerant unigenes had similar codon usage, and the highly expressed genes had higher usage frequency of optimal codons and lower GC content than the lowly expressed genes. In addition, there was no difference in the ENC values of salt-tolerant unigenes in H. ammodendron, and the expression level of the genes had no correlation with CAI. This study will help to elucidate the formation mechanism of H. ammodendron codon usage bias, and make contributions to the identification of new genes and the genetic engineering study on H. ammodendron.

Susceptibility to mice and potential evolutionary characteristics of porcine deltacoronavirus.

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes diarrhea in suckling piglets and has the potential for cross-species transmission, posing a threat to animal and human health. However, the susceptibility profile of different species of mice to PDCoV infection and its evolutionary characteristics are still unclear. In the current study, we found that BALB/c and Kunming mice are susceptible to PDCoV. Our results showed that there were obvious lesions in intestinal and lung tissues from the infected mice. PDCoV RNAs were detected in the lung, kidney, and intestinal tissues from the infected mice of both strains, and there existed wider tissue tropism in the PDCoV-infected BALB/c mice. The RNA and protein levels of aminopeptidase N from micewere relatively high in the kidney and intestinal tissues and obviously increased after PDCoV infection. The viral-specific IgG and neutralizing antibodies against PDCoV were detected inthe serum of infected mice. An interesting finding was thattwo key amino acid mutations, D138H and Q641K, in the S protein were identified in the PDCoV-infected mice. The essential roles of these two mutations for PDCoV-adaptive evolution were confirmed by cryo-electron microscope structure model analysis. The evolutionary characteristics of PDCoV among Deltacoronaviruses (δ-CoVs) were further analyzed. δ-CoVs from multiple mammals are closely related based on the phylogenetic analysis. The codon usage analysis demonstrated that similar codon usage patterns were used by most of the mammalian δ-CoVs at the global codon, synonymous codon, and amino acid usage levels. These results may provide more insights into the evolution, host ranges, and cross-species potential of PDCoV.

Codon usage of host-specific P genotypes (VP4) in group A rotavirus

BackgroundGroup A rotavirus (RVA) is a common causative agent of acute gastroenteritis in infants and young children worldwide. RVA P genotypes, determined by VP4 sequences, have been confirmed to infect humans and animals. However, their codon usage patterns that are essential to obtain insights into the viral evolution, host adaptability, and genetic characterization remained unclear, especially across animal hosts.ResultsWe performed a comprehensive codon usage analysis of eight host-specific RVA P genotypes, including human RVA (P[4] and P[8]), porcine RVA (P[13] and P[23]), and zoonotic RVA (P[1], P[6], P[7] and P[19]), based on 233 VP4 complete coding sequences. Nucleotide composition, relative synonymous codon usage (RSCU), and effective number of codons (ENC) were calculated. Principal component analysis (PCA) based on RSCU values was used to explore the codon usage patterns of different RVA P genotypes. In addition, mutation pressure and natural selection were identified by using ENC-plot, parity rule 2 plot, and neutrality plot analyses. All VP4 sequences preferred using A/U nucleotides (A: 0.354-0.377, U: 0.267-0.314) than G/C nucleotides across genotypes. Similarly, majority of commonly used synonymous codons were likely to end with A/U nucleotides (A: 9/18-12/18, U: 6/18-9/18). In PCA, human, porcine, and zoonotic genotypes clustered separately in terms of RSCU values, indicating the host-specific codon usage patterns; however, porcine and zoonotic genotypes were partly overlapped. Human genotypes, P[4] and P[8], had stronger codon usage bias, as indicated by more over-represented codons and lower ENC, compared to porcine and zoonotic genotypes. Moreover, natural selection was determined to be a predominant driver in shaping the codon usage bias across the eight P genotypes. In addition, mutation pressure contributed to the codon usage bias of human genotypes.ConclusionsOur study identified a strong codon usage bias of human RVA P genotypes attributable to both natural selection and mutation pressure, whereas similar codon usage bias between porcine and zoonotic genotypes predominantly attributable to natural selection. It further suggests possible cross-species transmission. Therefore, it warrants further surveillance of RVA P genotypes for early identification of zoonotic infection.