Analysis of codon usage patterns in complete plastomes of four medicinal Polygonatum species (Asparagaceae).

Polygonati Rhizoma and Polygonati odorati Rhizoma, known as "Huangjing" and "Yuzhu" in China, are medicinal Polygonatum species resources with top-grade medical and edible properties. The chloroplast (cp) genome has been used to study species diversity, evolution, and breeding of species for applications in genetic engineering. Codon usage bias (CUB), a common and complex natural phenomenon, is essential for studies of codon optimization of exogenous genes, genetic engineering, and molecular evolution. However, the CUB of medicinal Polygonatum species chloroplast genomes has not been systematically studied. In our study, a detailed analysis of CUB was performed in the medicinal Polygonatum species chloroplast genomes. We investigated the codon bias of 204 plastid protein-coding genes (PCGs) in 4 medicinal Polygonatum species using CodonW and CUSP online software. Through the analysis of the codon bias index, we found that the medicinal Polygonatum species chloroplast genomes had weak codon usage bias. In addition, our results also showed a high preference for AT bases in medicinal Polygonatum species chloroplast genomes, and the preference to use AT-ending codons was observed in these species chloroplast genomes. The neutrality plot, ENC plot, PR2-Bias plot, and correspondence analysis showed that compared with mutation pressure, natural selection was the most important factor of CUB. Based on the comparative analysis of high-frequency codons and high expression codons, we also determined the 10-11 optimal codons of investigative medicinal Polygonatum species. Furthermore, the result of RSCU-based cluster analysis showed that the genetic relationship between different medicinal Polygonatum species could be well reflected. This study provided an essential understanding of CUB and evolution in the medicinal Polygonatum species chloroplast genomes.

Mitochondrial genomes of Macropsini (Hemiptera: Cicadellidae: Eurymelinae): Structural features, codon usage patterns, and phylogenetic implications.

Macropsini is a tribe of Eurymelinae in the family Cicadellidae that is widely distributed worldwide. Still, its taxonomic status has been unstable, and the classification of certain clades at the genus level has been controversial. The aim of this study is to address the patterns and processes that explain the structure and the evolution of the mitogenomes of Macropsini, while contributing to the resolution of systematic issues involving five of their genera. To this task, the mitogenomes of 26 species of the tribe were sequenced and characterized, and their phylogenetic relationships were reconstructed. The results revealed that the nucleotide composition of mitochondrial genes in these 26 species was significantly skewed toward A and T. Codons ending with T or A in relative synonymous codon usage were significantly more prevalent than those ending with C or G. The parity plot, neutrality plot, and correspondence analysis revealed that mutation and selective pressure affect codon usage patterns. In the phylogenetic relationships of the Macropsini, the monophyly of Pedionis and Macropsis was well-supported. Meanwhile, Oncopsis revealed paraphyletic regarding Pediopsoides. In conclusion, this research not only contributes the valuable data to the understanding of the mitogenome of the Macropsini but also provides a reference for future investigations on codon usage patterns, potential adaptive evolution, and the phylogeny of the mitogenome within the subfamily Eurymelinae.

Exploring Codon Usage Patterns and Influencing Factors in Ranavirus DNA Polymerase Genes.

Ranaviruses, members of the genus Ranavirus within the family Iridoviridae, have become a significant concern for amphibian populations globally, along with other cold-blooded vertebrates, due to their emergence as a significant threat. We employed bioinformatics tools to examine the codon usage patterns in 61 DNA pol genes from Ranavirus, Lymphocystivirus, Megalocytivirus, and two unclassified ranaviruses, as no prior studies had been conducted on this topic. The results showed a slight or low level of codon usage bias (CUB) in the DNA pol genes of Ranavirus. Relative synonymous codon usage (RSCU) analysis indicated that the predominant codons favored in Ranavirus DNA pol genes terminate with C or G. Correlation analysis examining nucleotide content, third codon position, effective number of codons (ENC), correspondence analysis (COA), Aroma values, and GRAVY values indicated that the CUB across DNA pol genes could be influenced by both mutation pressure and natural selection. The neutrality plot indicated that natural selection is the primary factor driving codon usage. Furthermore, the analysis of the codon adaptation index (CAI) illustrated the robust adaptability of Ranavirus DNA pol genes to their hosts. Analysis of the relative codon deoptimization index (RCDI) suggested that Ranavirus DNA pol genes underwent greater selection pressure from their hosts. These findings will aid in comprehending the factors influencing the evolution and adaptation of Ranavirus to its hosts.

Mutation pressure mediates a pattern of substitution rates with latitude and climate in carnivores.

The evolutionary patterns of the mitochondrial genome are influenced by both adaptive and nonadaptive forces, with their contributions varying among taxa. There appears to be a correlation linking mutagenesis and latitude, which could be due to differences in metabolic rates. These discrepancies in metabolic rates exhibit a positive connection with mutation pressure. On this basis, we hypothesise that nonadaptive forces play a role in the differences in mutation rates observed along latitudinal gradients. In this study, we selected widely distributed carnivores as representatives of mammals to test our hypothesis. We examined the correlations between the dN/dS ratio (ω), as well as the substitution rates (dS and dN), of 13 PCGs in the mtDNA of 122 carnivores, and the latitude and climatic factors. We found that taxa distributed in higher latitudes tend to have higher substitution rates, but not ω values indicating selective pressure. Notably, dN shows a strong positive correlation with dS, although dS is primarily influenced by mutation pressure, while dN is also influenced by effective population size (N e ). Phylogenetic generalised least squares (PGLS) regression analyses showed that both substitution rates were correlated with climatic factors representing the temperature, precipitation and variability of climate. Based on our findings, we propose that the mutations are primarily influenced by nonadaptive forces (mutation pressure). This forms the fundamental premise for natural selection and speciation. Moreover, the correlation between substitution rates and latitudinal distribution and climate, which are outcomes of nonadaptive factors, can aid in comprehending the global distribution of species diversity.

Understanding the nucleotide composition and patterns of codon usage in the expression of human oral cancer genes.

Oral squamous cell carcinoma (OSCC) is primarily known as oral cancer (OC) that mostly occurs in mouth, lips and tongue. Mutations in some of the genes cause OC and some genes are risk factors for progression of OC. In this study, we analyzed the compositional features and pattern of codon usage in genes involved in OC using computational method as no work was reported yet. Compositional features suggested that the overall GC content was higher i.e. genes were GC rich. Effective number of codons (ENC) values ranged from 34.6 to 55.9 with a mean value of 49.03±4.22 representing low codon usage bias (CUB). Correspondence analysis (COA) suggested that the codon usage pattern was different in different genes. In genes associated with OC, highly significant correlation was observed between GC12 and GC3 (r=0.454, p<0.01) suggesting that directional mutation affected all the three codon positions. This is the first report on pattern of codon usage pattern on genes involved in OC, which not only alludes a new perspective for elucidating the mechanisms of biased usage of synonymous codons but also provide valuable clues for molecular genetic engineering.

Comparative Analysis of Codon Usage Bias in Six Eimeria Genomes.

The codon usage bias (CUB) of genes encoded by different species' genomes varies greatly. The analysis of codon usage patterns enriches our comprehension of genetic and evolutionary characteristics across diverse species. In this study, we performed a genome-wide analysis of CUB and its influencing factors in six sequenced Eimeria species that cause coccidiosis in poultry: Eimeria acervulina, Eimeria necatrix, Eimeria brunetti, Eimeria tenella, Eimeria praecox, and Eimeria maxima. The GC content of protein-coding genes varies between 52.67% and 58.24% among the six Eimeria species. The distribution trend of GC content at different codon positions follows GC1 > GC3 > GC2. Most high-frequency codons tend to end with C/G, except in E. maxima. Additionally, there is a positive correlation between GC3 content and GC3s/C3s, but a significantly negative correlation with A3s. Analysis of the ENC-Plot, neutrality plot, and PR2-bias plot suggests that selection pressure has a stronger influence than mutational pressure on CUB in the six Eimeria genomes. Finally, we identified from 11 to 15 optimal codons, with GCA, CAG, and AGC being the most commonly used optimal codons across these species. This study offers a thorough exploration of the relationships between CUB and selection pressures within the protein-coding genes of Eimeria species. Genetic evolution in these species appears to be influenced by mutations and selection pressures. Additionally, the findings shed light on unique characteristics and evolutionary traits specific to the six Eimeria species.

Selective and non-selective evolutionary signatures found in the simplest replicative biological entities.

Mitoviruses, which are considered evolutionary relics of extinct alpha-proteobacteria RNA phages, represent one of the simplest self-replicating biological systems. This study aims to quantitatively describe genomes and identify potential genomic signatures that support the protein phylogenetic-based classification criterion. Genomic variables, such as mononucleotide and dinucleotide composition, codon usage bias, and minimal free energy derived from optimized predicted RNA secondary structure, were analyzed. From the values obtained, the main evolutionary pressures were discussed, indicating that natural selection plays a significant role in shaping mitovirus genomes. However, neutral evolution also makes a significant contribution. This study reveals a significant discovery of structural divergence in Kvaramitovirus. The energy minimization approach employed to study 2D folding in this study reveals a distinct spatial organization of their genomes, providing evidence for the hypothesis of a single evolutionary event of circularization in the most recent common ancestor of the lineage. This hypothesis was discussed in light of recent discoveries by other researchers that partially support the existence of mitoviruses with circular genomes. Finally, this study represents a significant advancement in the understanding of mitoviruses, as it quantitatively describes the nucleotide sequence at the family and genus taxonomic levels. Additionally, we provide hypotheses that can be experimentally validated to inspire new research and address the gaps in knowledge of this fascinating, basally divergent RNA virus lineage.

Compositional Features and Codon Usage Pattern of Genes Associated with Parkinson's Disease.

Codon usage bias (CUB) is the phenomenon of non-uniform usage of synonymous codons in which some codons are more used than others and it helps in understanding the molecular organization of genome. Bioinformatic approach was used to analyze the protein-coding sequences of genes associated with Parkinson's disease (PD) to explore compositional features and codon usage pattern as no details work was reported yet. The average improved effective number of codons (Nc) and Nc prime were 42.74 and 44.26 respectively, indicated that CUB was low in these genes. In most of the genes, the overall GC content was almost 50% and GC content at the 1st codon position was the highest while GC content at the 2nd codon position was lowest. Relative synonymous codon usage (RSCU) analysis elucidated over-represented (p > 1.6) and under-represented codons (p < 0.6). The GTG (Val) is the only codon over-represented in all genes. Over-represented codons except (GTG) were A or T ending while under-represented codons (except ACT) were G or C ending. The codons namely TTA (Leu), CTA (Leu), ATC (Ile), ATA (Ile), AGT (Ser), AAC (Asn), TGT (Cys), TGC (Cys), CGC (Arg), AGA (Arg), and AGG (Arg) were absent in SNCA1 to SNCA8 genes. The codon TCG (Ser) was absent in all genes except UCHL1 and PINK1. Correspondence analysis (COA) revealed that the pattern of codon usage differs among genes associated with PD. Neutrality plot analysis indicated some of the points are diagonal distribution suggested that mutation pressure influenced the CUB in genes associated with PD.

Bioinformatic Analysis of Codon Usage Bias of HSP20 Genes in Four Cruciferous Species.

Heat shock protein 20 (HSP20) serves as a chaperone and plays roles in numerous biological processes, but the codon usage bias (CUB) of its genes has remained unexplored. This study identified 140 HSP20 genes from four cruciferous species, Arabidopsis thaliana, Brassica napus, Brassica rapa, and Camelina sativa, that were identified from the Ensembl plants database, and we subsequently investigated their CUB. As a result, the base composition analysis revealed that the overall GC content of HSP20 genes was below 50%. The overall GC content significantly correlated with the constituents at three codon positions, implying that both mutation pressure and natural selection might contribute to the CUB. The relatively high ENc values suggested that the CUB of the HSP20 genes in four cruciferous species was relatively weak. Subsequently, ENc exhibited a negative correlation with gene expression levels. Analyses, including ENc-plot analysis, neutral analysis, and PR2 bias, revealed that natural selection mainly shaped the CUB patterns of HSP20 genes in these species. In addition, a total of 12 optimal codons (ΔRSCU > 0.08 and RSCU > 1) were identified across the four species. A neighbor-joining phylogenetic analysis based on coding sequences (CDS) showed that the 140 HSP20 genes were strictly and distinctly clustered into 12 subfamilies. Principal component analysis and cluster analysis based on relative synonymous codon usage (RSCU) values supported the fact that the CUB pattern was consistent with the genetic relationship at the gene level and (or) species levels. These results will not only enrich the HSP20 gene resource but also advance our understanding of the CUB of HSP20 genes, which may underlie the theoretical basis for exploration of their genetic and evolutionary pattern.

Analysis of codon usage bias of exonuclease genes in invertebrate iridescent viruses.

Invertebrate iridescent viruses (IIVs) are double-stranded DNA viruses that belong to the Iridoviridae family. IIVs result diseases that vary in severity from subclinical to lethal in invertebrate hosts. Codon usage bias (CUB) analysis is a versatile method for comprehending the genetic and evolutionary aspects of species. In this study, we analyzed the CUB in 10 invertebrate iridescent viruses exonuclease genes by calculating and comparing the nucleotide contents, effective number of codons (ENC), codon adaptation index (CAI), relative synonymous codon usage (RSCU), and others. The results revealed that IIVs exonuclease genes are rich in A/T. The ENC analysis displayed a low codon usage bias in IIVs exonuclease genes. ENC-plot, neutrality plot, and parity rule 2 plot demonstrated that besides mutational pressure, other factors like natural selection, dinucleotide content, and aromaticity also contributed to CUB. The findings could enhance our understanding of the evolution of IIVs exonuclease genes.

The evolutionary characterization of Gamasida based on mitochondrial genes codon usage pattern.

Mites belonging to the suborder Gamasida are species-rich and habitat-diverse, with a worldwide distribution. To adapt to the environment and obtain better living conditions, all species of the suborder Gamasida have been undergoing constant evolution. The complete mitochondrial genome (mitogenome) is an invaluable molecular marker for studying the origin of species, genetic differentiation between closely related species, and between intraspecific groups. In some species of the suborder Gamasida, mitochondrial tRNA genes are truncated and carried unstable genetic information. This study presents a comparative analysis of codon usage pattern and preference of 13 protein-coding genes of 24 species in 17 genera and 10 families of the suborder Gamasida. Results showed that have an obvious AT preference (0.664-0.829) for codon usage in the suborder Gamasida. Most of the optimal and high-frequency codons also end in A/T. The degree of natural selection varies between the same protein-coding genes of different gamasid mites or among different protein-coding genes within the same gamasid mites. Base and codon usage pattern and preference are very similar between the same species and genus, namely the closer species, the more similar their bases and codons usage patterns and preference are. T bases and C bases were the preference bases for codon usage of 24 species in the suborder Gamasida. Evolution of the suborder Gamasida was dominated by natural selection (64.1%). This study provides the first comprehensive analysis of codon usage in the suborder Gamasida, which will greatly improve our understanding of codon usage patterns and preference, genetics, and evolution of the suborder Gamasida. It will help to evaluate the degree of molecular adaptation in the suborder Gamasida and to further explore evolutionary features of the suborder Gamasida.

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.

Insights into the Evolution and Host Adaptation of the Monkeypox Virus from a Codon Usage Perspective: Focus on the Ongoing 2022 Outbreak.

The exceptionally widespread outbreak of human monkeypox, an emerging zoonosis caused by the monkeypox virus (MPXV), with more than 69,000 confirmed cases in 100 non-endemic countries since 2022, is a major public health concern. Codon usage patterns reflect genetic variation and adaptation to new hosts and ecological niches. However, detailed analyses of codon usage bias in MPXV based on large-scale genomic data, especially for strains responsible for the 2022 outbreak, are lacking. In this study, we analyzed codon usage in MPXV and its relationship with host adaptation. We confirmed the ongoing outbreak of MPXVs belonging to the West Africa (WA) lineage by principal component analysis based on their codon usage patterns. The 2022 outbreak strains had a relatively low codon usage bias. Codon usage of MPXVs was shaped by mutation and natural selection; however, different from past strains, codon usage in the 2022 outbreak strains was predominantly determined by mutation pressure. Additionally, as revealed by the codon adaptation index (CAI), relative codon deoptimization index (RCDI), and similarity index (SiD) analyses, the codon usage patterns of MPXVs were also affected by their hosts. In particular, the 2022 outbreak strains showed slightly but significantly greater adaptation to many primates, including humans, and were subjected to stronger selection pressure induced by hosts. Our results suggest that MPXVs contributing to the 2022 outbreak have unique evolutionary features, emphasizing the importance of sustained monitoring of their transmission and evolution.

Codon Usage Bias Analysis in Macronuclear Genomes of Ciliated Protozoa.

Ciliated protozoa (ciliates) are unicellular eukaryotes, several of which are important model organisms for molecular biology research. Analyses of codon usage bias (CUB) of the macronuclear (MAC) genome of ciliates can promote a better understanding of the genetic mode and evolutionary history of these organisms and help optimize codons to improve gene editing efficiency in model ciliates. In this study, the following indices were calculated: the guanine-cytosine (GC) content, the frequency of the nucleotides at the third position of codons (T3, C3, A3, G3), the effective number of codons (ENc), GC content at the 3rd position of synonymous codons (GC3s), and the relative synonymous codon usage (RSCU). Parity rule 2 plot analysis, Neutrality plot analysis, ENc plot analysis, and correlation analysis were employed to explore the main influencing factors of CUB. The results showed that the GC content in the MAC genomes of each of 21 ciliate species, the genomes of which were relatively complete, was lower than 50%, and the base compositions of GC and GC3s were markedly distinct. Synonymous codon analysis revealed that the codons in most of the 21 ciliates ended with A or T and four codons were the general putative optimal codons. Collectively, our results indicated that most of the ciliates investigated preferred using the codons with anof AT-ending and that codon usage bias was affected by gene mutation and natural selection.

Codon usage bias of Venezuelan equine encephalitis virus and its host adaption.

Venezuelan equine encephalitis virus (VEEV) is an emerging zoonotic virus in the alphavirus genus. It can be transmitted to humans due to spillover from equid-mosquito cycles. The symptoms caused by VEEV include fever, headache, myalgia, nausea, and vomiting. It can also cause encephalitis in severe cases. The evolutionary features of VEEV are largely unknown. In this study, we comprehensively analyzed the codon usage pattern of VEEV by computing a variety of indicators, such as effective number of codons (ENc), codon adaptation index (CAI), relative synonymous codon usage (RSCU), on 130 VEEV coding sequences retrieved from GenBank. The results showed that the codon usage bias of VEEV is relatively low. ENc-GC3s plot, neutrality plot, and CAI-ENc correlation analyses supported that translational selection plays an important role in shaping the codon usage pattern of VEEV whereas the mutation pressure has a minor influence. Analysis of RSCU values showed that most of the preferred codons in VEEV are C/G-ended. Analysis of dinucleotide composition found that all CG- and UA-containing codons are not preferentially used. Phylogenetic analysis showed that VEEV isolates can be clustered into three genera and evolutionary force affects the codon usage pattern. Furthermore, a correspondence analysis (COA) showed that aromaticity and hydrophobicity as well as geographical distribution also have certain effects on the codon usage variation of VEEV, suggesting the possible involvement of translational selection. Overall, the codon usage of VEEV is comparatively slight and translational selection might be the main factor that shapes the codon usage pattern of VEEV. This study will promote our understanding about the evolution of VEEV and its host adaption, and might provide some clues for preventing the cross-species transmission of VEEV.

Comparative analysis of codon usage patterns in chloroplast genomes of ten Epimedium species.

BACKGROUND: The Phenomenon of codon usage bias exists in the genomes of prokaryotes and eukaryotes. The codon usage pattern is affected by environmental factors, base mutation, gene flow and gene expression level, among which natural selection and mutation pressure are the main factors. The study of codon preference is an effective method to analyze the source of evolutionary driving forces in organisms. Epimedium species are perennial herbs with ornamental and medicinal value distributed worldwide. The chloroplast genome is self-replicating and maternally inherited which is usually used to study species evolution, gene expression and genetic transformation. RESULTS: The results suggested that chloroplast genomes of Epimedium species preferred to use codons ending with A/U. 17 common high-frequency codons and 2-6 optimal codons were found in the chloroplast genomes of Epimedium species, respectively. According to the ENc-plot, PR2-plot and neutrality-plot, the formation of codon preference in Epimedium was affected by multiple factors, and natural selection was the dominant factor. By comparing the codon usage frequency with 4 common model organisms, it was found that Arabidopsis thaliana, Populus trichocarpa, and Saccharomyces cerevisiae were suitable exogenous expression receptors. CONCLUSION: The evolutionary driving force in the chloroplast genomes of 10 Epimedium species probably comes from mutation pressure. Our results provide an important theoretical basis for evolutionary analysis and transgenic research of chloroplast genes.

Codon usage bias in chloroplast genes implicate adaptive evolution of four ginger species.

Codon usage bias (CUB) refers to different codons exhibiting varying frequencies of usage in the genome. Studying CUB is crucial for understanding genome structure, function, and evolutionary processes. Herein, we investigated the codon usage patterns and influencing factors of protein-coding genes in the chloroplast genomes of four sister genera (monophyletic Roscoea and Cautleya, and monophyletic Pommereschea and Rhynchanthus) from the Zingiberaceae family with contrasting habitats in southwestern China. These genera exhibit distinct habitats, providing a unique opportunity to explore the adaptive evolution of codon usage. We conducted a comprehensive analysis of nucleotide composition and codon usage on protein-coding genes in the chloroplast genomes. The study focused on understanding the relationship between codon usage and environmental adaptation, with a particular emphasis on genes associated with photosynthesis. Nucleotide composition analysis revealed that the overall G/C content of the coding genes was ˂ 48%, indicating an enrichment of A/T bases. Additionally, synonymous and optimal codons were biased toward ending with A/U bases. Natural selection is the primary factor influencing CUB characteristics, particularly photosynthesis-associated genes. We observed differential gene expressions related to light adaptation among sister genera inhabiting different environments. Certain codons were favored under specific conditions, possibly contributing to gene expression regulation in particular environments. This study provides insights into the adaptive evolution of these sister genera by analyzing CUB and offers theoretical assistance for understanding gene expression and regulation. In addition, the data support the relationship between RNA editing and CUB, and the findings shed light on potential research directions for investigating adaptive evolution.

Analysis of codon usage bias of lumpy skin disease virus causing livestock infection.

Lumpy skin disease virus (LSDV) causes lumpy skin disease (LSD) in livestock, which is a double-stranded DNA virus that belongs to the genus Capripoxvirus of the family Poxviridae. LSDV is an important poxvirus that has spread out far and wide to become distributed worldwide. It poses serious health risks to the host and causes considerable negative socioeconomic impact on farmers financially and on cattle by causing ruminant-related diseases. Previous studies explained the population structure of the LSDV within the evolutionary time scale and adaptive evolution. However, it is still unknown and remains enigmatic as to how synonymous codons are used by the LSDV. Here, we used 53 LSDV strains and applied the codon usage bias (CUB) analysis to them. Both the base content and the relative synonymous codon usage (RSCU) analysis revealed that the AT-ended codons were more frequently used in the genome of LSDV. Further low codon usage bias was calculated from the effective number of codons (ENC) value. The neutrality plot analysis suggested that the dominant factor of natural selection played a role in the structuring of CUB in LSDV. Additionally, the results from a comparative analysis suggested that the LSDV has adapted host-specific codon usage patterns to sustain successful replication and transmission chains within hosts (Bos taurus and Homo sapiens). Both natural selection and mutational pressure have an impact on the codon usage patterns of the protein-coding genes in LSDV. This study is important because it has characterized the codon usage pattern in the LSDV genomes and has provided the necessary data for a basic evolutionary study on them.

Analysis of the Compositional Features and Codon Usage Pattern of Genes Involved in Human Autophagy.

Autophagy plays an intricate role in paradigmatic human pathologies such as cancer, and neurodegenerative, cardiovascular, and autoimmune disorders. Autophagy regulation is performed by a set of autophagy-related (ATG) genes, first recognized in yeast genome and subsequently identified in other species, including humans. Several other genes have been identified to be involved in the process of autophagy either directly or indirectly. Studying the codon usage bias (CUB) of genes is crucial for understanding their genome biology and molecular evolution. Here, we examined the usage pattern of nucleotide and synonymous codons and the influence of evolutionary forces in genes involved in human autophagy. The coding sequences (CDS) of the protein coding human autophagy genes were retrieved from the NCBI nucleotide database and analyzed using various web tools and software to understand their nucleotide composition and codon usage pattern. The effective number of codons (ENC) in all genes involved in human autophagy ranges between 33.26 and 54.6 with a mean value of 45.05, indicating an overall low CUB. The nucleotide composition analysis of the autophagy genes revealed that the genes were marginally rich in GC content that significantly influenced the codon usage pattern. The relative synonymous codon usage (RSCU) revealed 3 over-represented and 10 under-represented codons. Both natural selection and mutational pressure were the key forces influencing the codon usage pattern of the genes involved in human autophagy.

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.