Codon Usage Analysis Research Articles

Comparative Analysis of Mitochondrial Genomes between the B-Type Cytoplasmic Male Sterility Line and Its Maintainer Line in Wheat

Cytoplasmic male sterility (CMS) is a complex phenomenon in plants, rendering them unable to produce functional pollen. In general, this is caused by an abnormal or dysfunctional mitochondrial genome. In wheat, however, the systematic structural characteristics of the mitochondrial genome from the CMS line, vis-à-vis its maintainer line, are rarely reported. Here, we identified the morphological characteristics, sequenced, assembled, and characterized the complete mitogenomes of the wheat B-type CMS line (B) and its maintainer line (YS9). The morphological results indicated that the B likely undergoes binucleate microspore abortion. The B and YS9 genomes were assembled into a typical circular molecule 452,794 and 452,453 bp in length, respectively, comprising 34 protein-coding genes (PCGs), 3 ribosomal RNA genes (rRNAs), and 16 transfer RNA genes (tRNAs). The codon usage analysis revealed leucine (Leu) and serine (Ser) as the most frequently used amino acid residues in the B and YS9 mitochondrial proteins. In particular, we uncovered a specific ORF2718, whose length of 501 bp was more 30 bp than that of the atp8 gene in the B genome, which perhaps could affect normal function of ATP8. Further, the existence of SNPs at the atp6 gene is probably associated with the CMS mechanism. This study suggests that sequencing and comparing the genomic features of the B and YS9 mitogenomes provides not only an important opportunity to conduct further genomic breeding studies, but also valuable information for future evolutionary and molecular studies of CMS in wheat.

Identification of the Complete Chloroplast Genome of Malus zhaojiaoensis Jiang and Its Comparison and Evolutionary Analysis with Other Malus Species.

The genus Malus is rich in species and many of its plastid genomes have been released. However, limited resources and few markers are not conducive to the comparison of differences among species and resource identification and evaluation. In this study, the complete chloroplast genome of Malus zhaojiaoensis was studied by NGS sequencing, with a total length of 159998 bp. It consists of four regions, LSC (88,070 bp), IRB (26,359 bp), SSC (19,210 bp) and IRA (26,359 bp). M. zhaojiaoensis cp genome contained a total of 111 genes made up of three classes: 78 coding sequences, 29 tRNA genes, and four rRNA genes. In addition, a total of 91 SSRs and 43 INEs were found in the M. zhaojiaoensis cp genome, which was slightly different from M. baccata and M. hupehensis in number. The analysis of codon usage and RNA editing showed that high-frequency codons tended to end at A/U bases and RNA editing mainly occurred at the second codon. Comparative genome analysis suggested that the cp genomes of eight Malus species had higher overall similarity, but there were more variation hotspots (rps16_trnK-UUU, trnG-UCC_atpA, atpH_atpF, trnT-GGU_psbD, etc.) in the LSC region. By building evolutionary trees, it can be clearly observed that M. zhaojiaoensis formed a large group with eight species of Malus, but was relatively independent in differentiation. In conclusion, this study provides high-quality chloroplast genome resources of M. zhaojiaoensis and discusses the genetic variation characteristics of Malus genus. The findings of this study will provide a good reference for plastid genome assembly and interspecific comparison in the future.

Comparative Analyses of Two Nearly Complete Mitochondrial Genomes of the Liu’s Skink, <i>Plestiodon liui</i>, from South and North Sides of the Yangtze River

In this study we amplified and sequenced the nearly complete mitochondrial DNA of an individual of the Liu’s skink, Plestiodon liui, from south of the Yangtze River. The obtained mitochondrial genome was 17, 945 bp in length, comprising 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes and an incomplete control region (D-loop). Another nearly complete mitogenome of P. liui, from north of the Yangtze River, was retrieved from GenBank and used for comparative analyses. The results showed that the genome organization, base composition, codon usage, and gene arrangement of the mitochondrial genomes for the two individuals of P. liui were highly similar to each other. Twelve out of 13 PCGs initiated with canonical start codon (ATG), while COX1 started with GTG. The codon usage analysis revealed a preferential use of the LeuCUN, Pro, and Thr codons with the A/U ending. Among the 22 tRNA genes, only tRNA-SerAGY was not folded into a typical cloverleaf secondary structure and had no recognizable DHU stem. The phylogenetic tree inferred from Bayesian inference and maximum likelihood approaches strongly supported that the two individuals of P. liui clustered together, and formed the sister taxon to a clade of P. capito and P. tunganus. All PCGs had undergone a strong purifying selection, whereas 27 residues of the ATP6, COX2, Cytb, ND3, ND4, ND5, ND6 genes might have undergone positive selection. Bayesian molecular dating indicated that the split between P. liui and P. capito – P. tunganus was approximately 9.62 million years ago (Ma). Meanwhile, the coalescence time of the two individuals of P. liui was estimated to be 2.26 Ma with 95% highest posterior density of 1.32 – 3.28 Ma, which fell within the timeframe for the Yangtze River run-through between the late Pliocene to the middle Pleistocene. This finding implied that the Yangtze River run-through had played an important role in the diversification of the Liu’s skink.

Gene rearrangement in the mitogenome of whiteflies (Hemiptera: Aleyrodinae) along with their phylogeny and characterization of complete mitogenome of Aleurodicus rugioperculatus.

Mitochondrial genome rearrangements have been used for defining evolutionary relationships, but there have been incidences of convergences at different taxonomic levels. To gain new insights into whitefly mitogenome evolution, gene arrangement and phylogeny, we sequenced the complete mitogenome of Aleurodicus rugioperculatus (Aleyrodidae: Aleurodicinae) and conducted a comparative analysis with the previously published mitogenomes across the family Aleyrodidae. The complete mitogenome of Aleurodicus rugioperculatus was generated by Next generation sequencing method. It is 15,060bp circular molecule with 86.5A + T and 5.5% G + C content. It contains 37 genes (13 PCGs, two rRNAs, 22 tRNAs) and a non-coding control region (CR). Comparative analysis of codon usage indicated that the subfamily Aleyrodinae have weaker bias than Aleurodicinae. Bayesian Inference (BI) and Maximum Likelihood (ML) phylogenetic analyses yielded similar topologies supporting the monophyly of Aleyrodinae and Aleurodicinae. The gene order of 13 whiteflies was compared with ancestor to examine the plesiomorphies, synapomorphies and autapomorphies. We identified five gene blocks (I-V) in the whitefly ancestor that are shared plesiomorphies retained in different whitefly lineages. Gene block I is conserved in all whiteflies except three species. Conversely, we detected 83 derived gene boundaries within the family. Mapping these gene boundaries onto a phylogenetic tree revealed that 16 were symplesiomorphies for two subfamilies; 9 were synapomorphies between the species, and 28 autapomorphies for individual species. Comparative analyses of gene order of whiteflies revealed the derived gene boundaries which can be further investigated with more mitogenome data to examine the genome evolution in whiteflies.

Comparative Analysis of Codon Bias in the Chloroplast Genomes of Theaceae Species.

Theaceae species are dicotyledonous angiosperms with extremely high ornamental and economic value. The chloroplast genome is traditionally used to study species evolution, expression of chloroplast genes and chloroplast transformation. Codon usage bias (CUB) analysis is beneficial for investigations of evolutionary relationships and can be used to improve gene expression efficiency in genetic transformation research. However, there are relatively few systematic studies of the CUB in the chloroplast genomes of Theaceae species. In this study, CUB and nucleotide compositions parameters were determined by the scripts written in the Perl language, CodonW 1.4.2, CU.Win2000, RStudio and SPSS 23.0. The chloroplast genome data of 40 Theaceae species were obtained to analyse the codon usage (CU) characteristics of the coding regions and the influence of the source of variation on CUB. To explore the relationship between the CUB and gene expression levels in these 40 Theaceae plastomes, the synonymous codon usage order (SCUO) and measure independent of length and composition (MILC) values were determined. Finally, phylogenetic analysis revealed the genetic evolutionary relationships among these Theaceae species. Our results showed that based on the chloroplast genomes of these 40 Theaceae species, the CUB was for codons containing A/T bases and those that ended with A/T bases. Moreover, there was great commonality in the CUB of the Theaceae species according to comparative analysis of relative synonymous codon usage (RSCU) and relative frequency of synonymous codon (RFSC): these species had 29 identical codons with bias (RSCU > 1), and there were 19 identical high-frequency codons. The CUB of Theaceae species is mainly affected by natural selection. The SCUO value of the 40 Theaceae species was 0.23 or 0.24, and the chloroplast gene expression level was moderate, according to MILC values. Additionally, we observed a positive correlation between the SCUO and MILC values, which indicated that CUB might affect gene expression. Furthermore, the phylogenetic analysis showed that the evolutionary relationships in these 40 Theaceae species were relatively conserved. A systematic study on the CUB and expression of Theaceae species provides further evidence for their evolution and phylogeny.

Characterization of the complete chloroplast genome of Brassica oleracea var. italica and phylogenetic relationships in Brassicaceae.

Broccoli (Brassica oleracea var. italica) is an important B. oleracea cultivar, with high economic and agronomic value. However, comparative genome analyses are still needed to clarify variation among cultivars and phylogenetic relationships within the family Brassicaceae. Herein, the complete chloroplast (cp) genome of broccoli was generated by Illumina sequencing platform to provide basic information for genetic studies and to establish phylogenetic relationships within Brassicaceae. The whole genome was 153,364 bp, including two inverted repeat (IR) regions of 26,197 bp each, separated by a small single copy (SSC) region of 17,834 bp and a large single copy (LSC) region of 83,136 bp. The total GC content of the entire chloroplast genome accounts for 36%, while the GC content in each region of SSC,LSC, and IR accounts for 29.1%, 34.15% and 42.35%, respectively. The genome harbored 133 genes, including 88 protein-coding genes, 37 tRNAs, and 8 rRNAs, with 17 duplicates in IRs. The most abundant amino acid was leucine and the least abundant was cysteine. Codon usage analyses revealed a bias for A/T-ending codons. A total of 35 repeat sequences and 92 simple sequence repeats were detected, and the SC-IR boundary regions were variable between the seven cp genomes. A phylogenetic analysis suggested that broccoli is closely related to Brassica oleracea var. italica MH388764.1, Brassica oleracea var. italica MH388765.1, and Brassica oleracea NC_0441167.1. Our results are expected to be useful for further species identification, population genetics analyses, and biological research on broccoli.

Characterization of the Complete Chloroplast Genome of the Dragonhead Herb, Dracocephalumheterophyllum (Lamiaceae), and Comparative Analyses with Related Species

Dracocephalum heterophyllum (Lamiaceae: tribe Mentheae) is an annual aromatic herb native to East Asia with a long record of human uses, including medicinal, alimentary, and ornamental values. However, no information is available about its molecular biology, and no genomic study has been performed on D. heterophyllum. Here, we report the complete chloroplast (cp) genome of D. heterophyllum and a series of comparative genomic analyses between this and closely related species of Lamiaceae. Results indicated that the cp genome has a typical circular structure of 150,869 bp in length, consisting of a long single-copy (LSC) region with 82,410 bp, a short single-copy (SSC) region with 17,098 bp, and two inverted repeat (IR) regions of 51,350 bp. A total of 133 genes were identified, including 37 tRNA genes, 8 rRNA genes and 88 protein-coding genes, with a GC content of 37.8%. The gene content, organization, and GC values observed here were similar to those of other Dracocephalum species. We detected 99 different simple sequence repeat loci, and the codon usage analysis revealed a preferential use of the Leu codon with an A/U ending. Comparative analysis of cp genome sequences revealed five highly variable regions with remarkably higher Pi values (>0.03). The mean Ka/Ks between D. heterophyllum and three other Dracocephalum species ranged from 0.01079 (psbB) to 1.0497 (ycf2). Two cp genes, ycf2 and rps11, were proven to have high ratios of Ka/Ks, implying that cp genes may had undergone positive selection in the evolutionary history. We performed multiple sequence alignments using the cp genome of 22 species and constructed maximum likelihood (ML) and Bayesian trees, and found that D. heterophyllum were more closely related to D. moldavica and D. palmatum. In addition, the phylogenetic relationships between Dracocephalum and other members of Lamiaceae were consistent with previous results. These results are valuable for further formulating effective strategies of conservation and management for species in Dracocephalum, as well as providing a foundation for future research on the genetic resources of Dracocephalum.

Niche adaptation of Frankia do not drastically influence their metabolic profiling

ABSTRACT Metabolic-profiling (metabolomics/metabonomics) is a measurement strategy among biological systems for low-molecular-weight metabolites and their corresponding intermediates acting as dynamic physiological, pathophysiological and developmental stimuli. Information regarding the metabolomics of Frankia is elusive. In this study, we analyzed 48 Frankia whole-genome sequences. Kyoto Encyclopedia of Genes and Genomes (KEGG) database and KEGG Automatic Annotation Server (KAAS) were used for the prediction and functional annotation of genes associated with diverse metabolic pathways. Comprehensive codon and amino-acid usage analyses along with tRNA adaptation index and dN/dS-based evolutionary inquest were performed. We have used the Database-of-Essential-Genes (DEG) server to predict the essentiality of the metabolic pathway-related-genes. We found a strong effect of compositional constraints on the metabolic pathway genes of Frankia. The evolutionary analysis revealed the conserved nature of the studied genes. Since the metabolic pathway-related genes were found to be housekeeping genes, they are conserved and less evolved. This was further validated with a dN/dS value of less than 1. Moreover, the number of synonymous changes was more than non-synonymous changes so that the amino acid sequence remains identical. The cluster of orthologs (COG) analysis revealed “metabolism” as the main functional category of the studied gene set. The core metabolic pathway-related genes among considered Frankia strains accumulated 115 genes. This study for the first time reveals the genomic characteristics of the metabolic pathway-related genes among Frankia. From all the analysis, we could hypothesize that in spite of their host specificity and differential taxonomical distribution, Frankia maintain a core metabolic proficiency among them.

Complete chloroplast genome of Calligonum mongolicum Turcz. and comparative analysis with other Calligonum species

The perennial shrub of Calligonum mongolicum Turcz. is a dominant native plant in all Calligonum species, which has the largest and most widespread geographic distribution in arid deserts of northern China. Understanding the phylogenetic relationship between C. mongolicum and closely related plant species will offer guidance on the classification and identification of inter-species and their varieties. The chloroplast (cp) genome is an optimal model to decipher phylogenetic relationships in related plant families. In the present study, the complete cp genome of C. mongolicum was sequenced and compared with other Calligonum species. The cp genome of C. mongolicum was 162,124 bp in length with a quadripartite structure. A total of 131 functional genes were annotated, 14 different genes of which harbored introns and exons, 50 long repeat sequences and 244 simple sequences repeats were identified. Synonymous codon usage (SCU) analysis of C. mongolicum and other 8 Calligonum species exhibited similar change patterns, and natural selection would be crucial for SCU bias in all the 9 Calligonum species. The phylogenetic tree showed that C. mongolicum was clustered closely to Calligonum species. From the comparative analysis of genomic structures, the inverted repeat regions (IRa and IRb) were less divergent than other parts and coding regions was relatively conserved than non-coding regions. Compared to other Calligonum species, the IR region of C. mongolicum had a slight contraction. Our results comprehensively depict the architecture of C. mongolicum cp genome, and will lay a vigorous foundation for further study on molecular marker selection, phylogenetic analysis, and population researches in Calligonum species.

Proteomic Characterization and Target Identification Against Streptococcus mutans Under Bacitracin Stress Conditions Using LC–MS and Subtractive Proteomics

The aim of the present study, is to identify potential targets against the highly pathogenic bacteria Streptococcus mutans that causes dental caries as well as the deadly infection of endocarditis. The powerful and highly sensitive technique of liquid chromatography-mass spectrometry (LC–MS/MS) identified 321 proteins of S. mutans when grown under stressful conditions induced by the antibiotic bacitracin. These 321 proteins were subjected to the insilico method of subtractive proteomics to screen out potential targets by utilizing different analyses like CD-HIT, non-homologous sequence screening, KEGG pathway, essentiality screening, gut-flora non-homology, and codon usage analysis. A database of essential proteins was employed to find sequence homology of non-paralogous proteins to determine proteins which are essential for bacterial survival. Cellular localization analysis of the selected proteins was done to localize them inside the cell along with physico-chemical characterization and druggability analysis. Using computational tools, 22 proteins out of 321, that are functionally distinguishable from their human counterparts and passed the criterion of a potential therapeutic candidate were identified. The selected proteins comprise central energy metabolic proteins, virulence factors, proteins of the sortase family, and essentiality factors. The presented analyses identified proteins of the sortase family, which appear as key therapeutic targets against caries infection. These proteins regulate a number of virulence factors, thus can be simultaneously inhibited to obstruct multiple virulence pathways.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1007/s10930-021-10038-1.

Comprehensive Analysis of Codon Usage Patterns in Chinese Porcine Circoviruses Based on Their Major Protein-Coding Sequences.

Porcine circoviruses (PCVs) are distributed in swine herds worldwide and represent a threat to the health of domestic pigs and the profits of the swine industry. Currently, four PCV species, including PCV-1, PCV-2, PCV-3 and PCV-4, have been identified in China. Considering the ubiquitous characteristic of PCVs, the new emerged PCV-4 and the large scale of swine breeding in China, an overall analysis on codon usage bias for Chinese PCV sequences was performed by using the major proteins coding sequences (ORF1 and ORF2) to better understand the relationship of these viruses with their host. The data from genome nucleotide frequency composition and relative synonymous codon usage (RSCU) analysis revealed an overrepresentation of AT pair and the existence of a certain codon usage bias in all PCVs. However, the values of an effective number of codons (ENC) revealed that the bias was of low magnitude. Principal component analysis, ENC-plot, parity rule two analysis and correlation analysis suggested that natural selection and mutation pressure were both involved in the shaping of the codon usage patterns of PCVs. However, a neutrality plot revealed a stronger effect of natural selection than mutation pressure on codon usage patterns. Good host adaptation was also shown by the codon adaptation index analysis for all these viruses. Interestingly, obtained data suggest that PCV-4 might be more adapted to its host compared to other PCVs. The present study obtained insights into the codon usage pattern of PCVs based on ORF1 and ORF2, which further helps the understanding the molecular evolution of these swine viruses.

Comparative and Phylogenetic Analysis of Complete Plastomes among Aristidoideae Species (Poaceae).

Simple SummaryAristidoideae is a subfamily of Poaceae, including three genera, Aristida, Stipagrostis, and Sartidia. In this study, the plastomes of Aristida adscensionis and Stipagrostis pennata were newly sequenced, and a total of 16 Aristidoideae plastomes were compared. All plastomes were conservative in genome size, gene number, structure, and IR boundary. Repeat sequence analysis showed that forward and palindrome repeats were the most common repeat types. The number of SSRs ranged from 30 (Sartidia isaloensis) to 54 (Aristida purpurea). Codon usage analysis showed that plastome genes preferred to use codons ending with A/T. A total of 12 highly variable regions were screened, including four protein coding sequences and eight non-coding sequences. All Maximum Likelihood and Bayesian Inference trees strongly support the monophyly of Aristidoideae and each of the three genera. Within Aristidoideae, Aristida is sister to the clade composed of Stipagrostis and Sartidia. The divergence between C4 Stipagrostis and C3 Sartidia was estimated at 11.04 Ma, which may be associated with the drought event in the Miocene period. Finally, the differences in carbon fixation patterns, geographical distributions, and ploidy may be related to the difference of species numbers among these three genera. This study provides insights into the phylogeny and evolution of the subfamily Aristidoideae.Aristidoideae is a subfamily in the PACMAD clade of family Poaceae, including three genera, Aristida, Stipagrostis, and Sartidia. In this study, the plastomes of Aristida adscensionis and Stipagrostis pennata were newly sequenced, and a total of 16 Aristidoideae plastomes were compared. All plastomes were conservative in genome size, gene number, structure, and IR boundary. Repeat sequence analysis showed that forward and palindrome repeats were the most common repeat types. The number of SSRs ranged from 30 (Sartidia isaloensis) to 54 (Aristida purpurea). Codon usage analysis showed that plastome genes preferred to use codons ending with A/T. A total of 12 highly variable regions were screened, including four protein coding sequences (matK, ndhF, infA, and rpl32) and eight non-coding sequences (rpl16-1-rpl16-2, ccsA-ndhD, trnY-GUA-trnD-GUC, ndhF-rpl32, petN-trnC-GCA, trnT-GGU-trnE-UUC, trnG-GCC-trnfM-CAU, and rpl32-trnL-UAG). Furthermore, the phylogenetic position of this subfamily and their intergeneric relationships need to be illuminated. All Maximum Likelihood and Bayesian Inference trees strongly support the monophyly of Aristidoideae and each of three genera, and the clade of Aristidoideae and Panicoideae was a sister to other subfamilies in the PACMAD clade. Within Aristidoideae, Aristida is a sister to the clade composed of Stipagrostis and Sartidia. The divergence between C4 Stipagrostis and C3 Sartidia was estimated at 11.04 Ma, which may be associated with the drought event in the Miocene period. Finally, the differences in carbon fixation patterns, geographical distributions, and ploidy may be related to the difference of species numbers among these three genera. This study provides insights into the phylogeny and evolution of the subfamily Aristidoideae.

Insight into the characteristics of an important evolutionary model bird (Geospiza magnirostris) mitochondrial genome through comparison

Darwin’s finches are the most classic case of evolution. Early studies on the evolution of this species were mainly based on morphology. Until now, the mitochondrial genome of Geospiza magnirostris has been sequenced and the study explored the characteristics of the complete genome of G. magnirostris and verified the evolutionary position of it. The 13 PCGs initiated by ATN codons. The stop codons of three PCGs (ND2, COX3 and ND4) were incomplete, with only T- or TA- replacing complete form TAA or TAG. All the tRNA genes expressed a typical cloverleaf secondary structure, except for tRNASer1(AGY), whose dihydrouridine (DHU) arm was lack and instead with a simple loop. In the sequence of the control region of G. magnirostris, we found six simple repeat tandem sequences with a total length of 42 bp. Two characteristic conserved overlapping junction (ATGCTAA) and (CAAGAAAG) were observed as reported for eight selected Passeriformes birds. A special conserved overlapping junction (ATCTTACC) involved in mitochondrial transcription termination was found between tRNATyr and COX1 in G. magnirostris’s control region. Four most frequently used amino acids in G. magnirostris’s PCGs were Leu1 (CUN), Ile, Thr, Ala. The codon usage of G. magnirostris was relatively average, and there was no particular bias. The ratio Ka/Ks results showed that G. magnirostris receives less natural selection pressure. The phylogenetic relationships and cluster analysis of relative codon usage showed that G. magnirostris and Thraupis episcopus clustered in one branch. The phylogenetic position of G. magnirostris was consistent with the traditional taxonomic of Thraupis. The results supported the conclusion that G. magnirostris belongs to the morphological classification of the family Thraupidae.

A comparative study of the chloroplast genomes of five Lepidium species with high medicinal value.

Plantgenomics is a rapidly developing field in medicinal plant research. This study analysed the relevant information of chloroplasts genome sequences of five medicinal plants from the genus Lepidium . We sequenced the complete chloroplast (cp) genomes of Lepidium apetalum Willd. and Lepidium perfoliatum Linnaeus., and assessed their genetic profiles against the reported profiles of Lepidium sativum Linnaeus., Lepidium meyenii Walp., and Lepidium virginicum Linn. We found that L. apetalum and L. perfoliatum possessed 130 distinct genes that included 85 protein-coding, 37 transfer RNA (tRNA), and eight ribosomal RNA (rRNA) genes. Our repeat analyses revealed that L. apetalum harboured 20 direct repeats, 16 palindrome repeats, 30 tandem repeats, and 87 simple sequence repeats, whereas, L. perfoliatum had 15 direct repeats, 20 palindrome repeats, four reverse repeats, 21 tandem repeats, and 98 simple sequence repeats. Using syntenic analysis, we also revealed a high degree of sequence similarity within the coding regions of Lepidium medicinal plant cp genomes, and a high degree of divergence among the intergenic spacers. Pairwise alignment and single-nucleotide polymorphism (SNP) examinations further revealed certain Lepidium -specific gene fragments. Codon usage analysis showed that codon 14 was the most frequently used codon in the Lepidium coding sequences. Further, correlation investigations suggest that L. apetalum and L. perfoliatum originate from similar genetic backgrounds. Analysis of codon usage bias of Lepidium cp genome was strongly influenced by mutation and natural selection. We showed that L. apetalum and L. perfoliatum will likely enhance breeding, species recognition, phylogenetic evolution, and cp genetic engineering of the Lepidium medicinal plants.

Lack of transcriptional coordination between mitochondrial and nuclear oxidative phosphorylation genes in the presence of two divergent mitochondrial genomes.

In most eukaryotes, oxidative phosphorylation (OXPHOS) is the main energy production process and it involves both mitochondrial and nuclear genomes. The close interaction between the two genomes is critical for the coordinated function of the OXPHOS process. Some bivalves show doubly uniparental inheritance (DUI) of mitochondria, where two highly divergent mitochondrial genomes, one inherited through eggs (F-type) and the other through sperm (M-type), coexist in the same individual. However, it remains a puzzle how nuclear OXPHOS genes coordinate with two divergent mitochondrial genomes in DUI species. In this study, we compared transcription, polymorphism, and synonymous codon usage in the mitochondrial and nuclear OXPHOS genes of the DUI species Ruditapes philippinarum using sex- and tissue-specific transcriptomes. Mitochondrial and nuclear OXPHOS genes showed different transcription profiles. Strong co-transcription signal was observed within mitochondrial (separate for F- and M-type) and within nuclear OXPHOS genes but the signal was weak or absent between mitochondrial and nuclear OXPHOS genes, suggesting that the coordination between mitochondrial and nuclear OXPHOS subunits is not achieved transcriptionally. McDonald-Kreitman and frequency-spectrum based tests indicated that M-type OXPHOS genes deviated significantly from neutrality, and that F-type and M-type OXPHOS genes undergo different selection patterns. Codon usage analysis revealed that mutation bias and translational selection were the major factors affecting the codon usage bias in different OXPHOS genes, nevertheless, translational selection in mitochondrial OXPHOS genes appears to be less efficient than nuclear OXPHOS genes. Therefore, we speculate that the coordination between OXPHOS genes may involve post-transcriptional/translational regulation.

De novo assembly and characterisation of chloroplast genomes of broccoli cvs. Marathon and Green sprout using next generation sequencing

The genus Brassica (family Brassicaceae) includes nutritionally and economically important species such as Brassica napus, Brassica rapa, and Brassica oleracea. Many varieties of B. oleracea are available in various morphological forms including nutritive vegetables such as cauliflower (var. botrytis), Brussels sprouts (var. gemmifera), kales and collards (var. acephala), kohlrabi (var. gongylodes), cabbage (var. capitata), and broccoli (var. italica). Objective of the present study was to sequence chloroplast genomes of two cultivars of broccoli: Marathon and Green sprout. The sequencing was done by next generation sequencing. The analysis was performed using Velvet, Geneious, GeSeq, tRNAscan-SE, ARAGORN, OrganellarGenomeDRAW, IRscope and REPuter. The genomes of both cultivars showed highly similar quadripartite structure of 153,365 bp. The LSC (83,136 bp) and SSC (17,835 bp) regions were separated by a pair of IR (26,197 bp) region. In total, 114 unique genes were present in both species, including 80 protein-coding, 30 tRNA and 4 rRNA genes, while 18 genes were duplicated in IRs. The highest amino acid encoding frequency was found for Leucine whereas cysteine was the least encoding amino acid. The codon usage analyses confirmed high encoding efficacy of codons that ended at 3'-end with A/T. Repeat analyses of these genomes revealed 415 microsatellites and 36 oligonucleotide repeats. Microsatellites motifs were mostly comprised of A/T instead of C/G. The comparative analyses confirmed the presence of 17 substitutions between both cultivars. Overall, this study will increase knowledge about the chloroplast genomes of broccoli and will provide a resource for chloroplast genetic engineering of this important edible plant.

Codon usage bias.

Codon usage bias is the preferential or non-random use of synonymous codons, a ubiquitous phenomenon observed in bacteria, plants and animals. Different species have consistent and characteristic codon biases. Codon bias varies not only with species, family or group within kingdom, but also between the genes within an organism. Codon usage bias has evolved through mutation, natural selection, and genetic drift in various organisms. Genome composition, GC content, expression level and length of genes, position and context of codons in the genes, recombination rates, mRNA folding, and tRNA abundance and interactions are some factors influencing codon bias. The factors shaping codon bias may also be involved in evolution of the universal genetic code. Codon-usage bias is critical factor determining gene expression and cellular function by influencing diverse processes such as RNA processing, protein translation and protein folding. Codon usage bias reflects the origin, mutation patterns and evolution of the species or genes. Investigations of codon bias patterns in genomes can reveal phylogenetic relationships between organisms, horizontal gene transfers, molecular evolution of genes and identify selective forces that drive their evolution. Most important application of codon bias analysis is in the design of transgenes, to increase gene expression levels through codon optimization, for development of transgenic crops. The review gives an overview of deviations of genetic code, factors influencing codon usage or bias, codon usage bias of nuclear and organellar genes, computational methods to determine codon usage and the significance as well as applications of codon usage analysis in biological research, with emphasis on plants.

Codon usage, phylogeny and binding energy estimation predict the evolution of SARS-CoV-2

In the frames of a One Health strategy, i.e. a strategy should be able to predict susceptibility to infection in both humans and animals, developing a SARS-CoV-2 mutation tracking system is a goal. We observed that the phylogenetic proximity of vertebrate ACE2 receptors does not affect the binding energy for the viral spike protein. However, all viral variants seem to bind ACE2 better in many animals than in humans. Moreover, two observations highlight that the evolution of the virus started at the beginning of 2020 and culminated with the appearance of the variants. First, codon usage analysis shows that the B.1.1.7 (alpha), B.1.351 (beta) and B.1.617.2 (delta) variants, similar in the use of codons, are also similar to a virus sampled in January 2020. Second, the host-specific D614G mutation becomes prevalent starting from March 2020. Overall, we show that SARS-CoV-2 undergoes a process of molecular evolution that begins with the optimization of codons followed by the functional optimization of the spike protein.

A detailed comparative analysis of codon usage bias in Alongshan virus

Alongshan virus (ALSV) is an emerging tick-borne pathogen that infects humans, causing febrile disease. ALSV uses Ixodes Persulcatus ticks to infect humans with a wide range of signs, from asymptomatic to encephalitis-like syndrome. There is an increasing public health concern about the ALSV infection. To get insight into the impacts of viral relations with their hosts on viral ability, survival, and evasion from hosts immune systems remain unknown. The codon usage is a driving force in viral genome evolution; therefore, we enrolled 41 ALSV strains in codon usage analysis to elucidate the molecular evolutionary dynamics of ALSV. The results indicate that the overall codon usage among ALSV isolates is relatively similar and slightly biased. Base compositions for the cds were in order of G >A >C >U and in the third position of codons G3 >A3 >C3 >T3. The RSCU values revealed that the more frequently used codons were mostly GC ended. Different codon preferences in ALSV genes in relation to codon usage of H. sapiens and Ixodes Persulcatus genes were found. Neutrality plot was determined to reveal the superiority of natural selection over directional mutation pressure in causing CUB based on GC12 versus GC3 contents. The results of these studies suggest that the emergence of ALSV in China, Russia and Finland may also be reflected in ALSV codon usage. Altogether, the presence of both mutation pressure and natural selection effect in shaping the codon usage patterns of ALSV.

Propagation of a De Novo Gene under Natural Selection: Antifreeze Glycoprotein Genes and Their Evolutionary History in Codfishes.

The de novo birth of functional genes from non-coding DNA as an important contributor to new gene formation is increasingly supported by evidence from diverse eukaryotic lineages. However, many uncertainties remain, including how the incipient de novo genes would continue to evolve and the molecular mechanisms underlying their evolutionary trajectory. Here we address these questions by investigating evolutionary history of the de novo antifreeze glycoprotein (AFGP) gene and gene family in gadid (codfish) lineages. We examined AFGP phenotype on a phylogenetic framework encompassing a broad sampling of gadids from freezing and non-freezing habitats. In three select species representing different AFGP-bearing clades, we analyzed all AFGP gene family members and the broader scale AFGP genomic regions in detail. Codon usage analyses suggest that motif duplication produced the intragenic AFGP tripeptide coding repeats, and rapid sequence divergence post-duplication stabilized the recombination-prone long repetitive coding region. Genomic loci analyses support AFGP originated once from a single ancestral genomic origin, and shed light on how the de novo gene proliferated into a gene family. Results also show the processes of gene duplication and gene loss are distinctive in separate clades, and both genotype and phenotype are commensurate with differential local selective pressures.