Analysis of codon usage bias of WRKY transcription factors in Helianthus annuus

Plastome evolution of Engelhardia facilitates phylogeny of Juglandaceae

BACKGROUND

Engelhardia (Juglandaceae) is a genus of significant ecological and economic importance, prevalent in the tropics and subtropics of East Asia. Although previous efforts based on multiple molecular markers providing profound insights into species delimitation and phylogeography of Engelhardia, the maternal genome evolution and phylogeny of Engelhardia in Juglandaceae still need to be comprehensively evaluated. In this study, we sequenced plastomes from 14 samples of eight Engelhardia species and the outgroup Rhoiptelea chiliantha, and incorporated published data from 36 Juglandaceae and six outgroup species to test phylogenetic resolution. Moreover, comparative analyses of the plastomes were conducted to investigate the plastomes evolution of Engelhardia and the whole Juglandaceae family.

RESULTS

The 13 Engelhardia plastomes were highly similar in genome size, gene content, and order. They exhibited a typical quadripartite structure, with lengths from 161,069 bp to 162,336 bp. Three mutation hotspot regions (TrnK-rps16, ndhF-rpl32, and ycf1) could be used as effective molecular markers for further phylogenetic analyses and species identification. Insertion and deletion (InDels) may be an important driving factor for the evolution of plastomes in Juglandoideae and Engelhardioideae. A total of ten codons were identified as the optimal codons in Juglandaceae. The mutation pressure mostly contributed to shaping codon usage. Seventy-eight protein-coding genes in Juglandaceae experienced relaxed purifying selection, only rpl22 and psaI genes showed positive selection (Ka/Ks > 1). Phylogenetic results fully supported Engelhardia as a monophyletic group including two sects and the division of Juglandaceae into three subfamilies. The Engelhardia originated in the Late Cretaceous and diversified in the Late Eocene, and Juglandaceae originated in the Early Cretaceous and differentiated in Middle Cretaceous. The phylogeny and divergence times didn't support rapid radiation occurred in the evolution history of Engelhardia.

CONCLUSION

Our study fully supported the taxonomic treatment of at the section for Engelhardia species and three subfamilies for Juglandaceae and confirmed the power of phylogenetic resolution using plastome sequences. Moreover, our results also laid the foundation for further studying the course, tempo and mode of plastome evolution of Engelhardia and the whole Juglandaceae family.

Genome-Wide Analysis of Serine Carboxypeptidase-like Genes in Soybean and Their Roles in Stress Resistance

The serine carboxypeptidase-like (SCPL) gene family plays a crucial role in the regulation of plant growth, development, and stress response through activities such as acyltransferases in plant secondary metabolism pathways. Although SCPL genes have been identified in various plant species, their specific functions and characteristics in soybean (Glycine max) have not yet been studied. We identified and characterized 73 SCPL genes, grouped into three subgroups based on gene structure and phylogenetic relationships. These genes are distributed unevenly across 20 soybean chromosomes and show varied codon usage patterns influenced by both mutation and selection pressures. Gene ontology (GO) enrichment suggests these genes are involved in plant cell wall regulation and stress responses. Expression analysis in various tissues and under stress conditions, including the presence of numerous stress-related cis-acting elements, indicated that these genes have varied expression patterns. This suggests that they play specialized roles such as modulating plant defense mechanisms against nematode infections, enhancing tolerance to drought and high salinity, and responding to cold stress, thereby helping soybean adapt to environmental stresses. Moreover, the expression of specific GmSCPLs was significantly affected following exposure to nematode infection, drought, high salt (NaCl), and cold stresses. Our findings underscore the potential of SCPL genes in enhancing stress resistance in soybean, providing a valuable resource for future genetic improvement and breeding strategies.

Codon usage characterization and phylogenetic analysis of the mitochondrial genome in Hemerocallis citrina

BACKGROUND

Hemerocallis citrina Baroni is a traditional vegetable crop widely cultivated in eastern Asia for its high edible, medicinal, and ornamental value. The phenomenon of codon usage bias (CUB) is prevalent in various genomes and provides excellent clues for gaining insight into organism evolution and phylogeny. Comprehensive analysis of the CUB of mitochondrial (mt) genes can provide rich genetic information for improving the expression efficiency of exogenous genes and optimizing molecular-assisted breeding programmes in H. citrina.

RESULTS

Here, the CUB patterns in the mt genome of H. citrina were systematically analyzed, and the possible factors shaping CUB were further evaluated. Composition analysis of codons revealed that the overall GC (GCall) and GC at the third codon position (GC3) contents of mt genes were lower than 50%, presenting a preference for A/T-rich nucleotides and A/T-ending codons in H. citrina. The high values of the effective number of codons (ENC) are indicative of fairly weak CUB. Significant correlations of ENC with the GC3 and codon counts were observed, suggesting that not only compositional constraints but also gene length contributed greatly to CUB. Combined ENC-plot, neutrality plot, and Parity rule 2 (PR2)-plot analyses augmented the inference that the CUB patterns of the H. citrina mitogenome can be attributed to multiple factors. Natural selection, mutation pressure, and other factors might play a major role in shaping the CUB of mt genes, although natural selection is the decisive factor. Moreover, we identified a total of 29 high-frequency codons and 22 optimal codons, which exhibited a consistent preference for ending in A/T. Subsequent relative synonymous codon usage (RSCU)-based cluster and mt protein coding gene (PCG)-based phylogenetic analyses suggested that H. citrina is close to Asparagus officinalis, Chlorophytum comosum, Allium cepa, and Allium fistulosum in evolutionary terms, reflecting a certain correlation between CUB and evolutionary relationships.

CONCLUSIONS

There is weak CUB in the H. citrina mitogenome that is subject to the combined effects of multiple factors, especially natural selection. H. citrina was found to be closely related to Asparagus officinalis, Chlorophytum comosum, Allium cepa, and Allium fistulosum in terms of their evolutionary relationships as well as the CUB patterns of their mitogenomes. Our findings provide a fundamental reference for further studies on genetic modification and phylogenetic evolution in H. citrina.

Novel Plastid Genome Characteristics in Fugacium kawagutii and the Trend of Accelerated Evolution of Plastid Proteins in Dinoflagellates

Typical (peridinin-containing) dinoflagellates possess plastid genomes composed of small plasmids named "minicircles". Despite the ecological importance of dinoflagellate photosynthesis in corals and marine ecosystems, the structural characteristics, replication dynamics, and evolutionary forcing of dinoflagellate plastid genomes remain poorly understood. Here, we sequenced the plastid genome of the symbiodiniacean species Fugacium kawagutii and conducted comparative analyses. We identified psbT-coding minicircles, features previously not found in Symbiodiniaceae. The copy number of F. kawagutii minicircles showed a strong diel dynamics, changing between 3.89 and 34.3 copies/cell and peaking in mid-light period. We found that F. kawagutii minicircles are the shortest among all dinoflagellates examined to date. Besides, the core regions of the minicircles are highly conserved within genus in Symbiodiniaceae. Furthermore, the codon usage bias of the plastid genomes in Heterocapsaceae, Amphidiniaceae, and Prorocentraceae species are greatly influenced by selection pressure, and in Pyrocystaceae, Symbiodiniaceae, Peridiniaceae, and Ceratiaceae species are influenced by both natural selection pressure and mutation pressure, indicating a family-level distinction in codon usage evolution in dinoflagellates. Phylogenetic analysis using 12 plastid-encoded proteins and five nucleus-encoded plastid proteins revealed accelerated evolution trend of both plastid- and nucleus-encoded plastid proteins in peridinin- and fucoxanthin-dinoflagellate plastids compared to plastid proteins of nondinoflagellate algae. These findings shed new light on the structure and evolution of plastid genomes in dinoflagellates, which will facilitate further studies on the evolutionary forcing and function of the diverse dinoflagellate plastids. The accelerated evolution documented here suggests plastid-encoded sequences are potentially useful for resolving closely related dinoflagellates.

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.

Adjustment of p-value expression to ontology using machine learning for genetic prediction, prioritization, interaction, and its validation in glomerular disease

The results of gene expression analysis based on p-value can be extracted and sorted by their absolute statistical significance and then applied to multiple similarity scores of their gene ontology (GO) terms to promote the combination and adjustment of these scores as essential predictive tasks for understanding biological/clinical pathways. The latter allows the possibility to assess whether certain aspects of gene function may be associated with other varieties of genes, to evaluate regulation, and to link them into networks that prioritize candidate genes for classification by applying machine learning techniques. We then detect significant genetic interactions based on our algorithm to validate the results. Finally, based on specifically selected tissues according to their normalized gene expression and frequencies of occurrence from their different biological and clinical inputs, a reported classification of genes under the subject category has validated the abstract (glomerular diseases) as a case study.

Evolution and Expression of the Expansin Genes in Emmer Wheat

Expansin proteins, a crucial class of intracellular proteins, are known to play a vital role in facilitating processes like cell wall relaxation and cell growth. Recent discoveries have revealed that expansin proteins also have significant functions in plant growth, development, and response to resistance. However, the expansin gene family, particularly in emmer wheat, has not been thoroughly studied, particularly in terms of evolution. In this study, we identified 63 TdEXPs and 49 TtEXPs from the latest genome versions of wild emmer wheat (WEW) and durum wheat (DW), respectively. The physicochemical properties of the encoded expansin proteins exhibited minimal differences, and the gene structures remained relatively conserved. Phylogenetic analysis categorized the proteins into three subfamilies, namely EXPA, EXPB, and EXLA, in addition to the EXLB subfamily. Furthermore, codon preference analysis revealed an increased usage frequency of the nucleotide "T" in expansin proteins throughout the evolution of WEW and DW. Collinearity analysis demonstrated higher orthology between the expansin proteins of WEW and DW, with a Ka/Ks ratio ranging from 0.4173 to 0.9494, indicating purifying selection during the evolution from WEW to DW. Haplotype analysis of the expansin gene family identified five genes in which certain haplotypes gradually became dominant over the course of evolution, enabling adaptation for survival and improvement. Expression pattern analysis indicated tissue-specific expression of expansin genes in emmer wheat, and some of these genes were quantified through qRT-PCR to assess their response to salt stress. These comprehensive findings present the first systematic analysis of the expansin protein gene family during the evolution from WEW to DW, providing a foundation for further understanding the functions and biological roles of expansin protein genes in emmer wheat.

Complete chloroplast genome structural characterization of two Phalaenopsis (Orchidaceae) species and comparative analysis with their alliance

BACKGROUND

The taxonomy and infrageneric delimitation of Phalaenopsis Blume has been significantly disputed due to some overlapping morphological features between species related, which needed further evidence for clarification. The structural characterization of complete chloroplast genomes of P. storbatiana and P. wilsonii were analyzed and compared with those of related taxa to provide a better understanding of their genomic information on taxonomy and phylogeny.

RESULTS

It was shown that chloroplast genomes of Phalaenopsis storbatiana and P. wilsonii had a typical quadripartite structure with conserved genome arrangements and moderate divergence. The chloroplast genomes of P. storbatiana and P. wilsonii were 145,885 bp and 145,445 bp in length, respectively, and shared a similar GC content of 36.8%. Gene annotations of two species revealed 109 single-copy genes consistently. In addition, 20 genes duplicated in the inverted regions, 16 genes each possessed one or more introns, and five ndh (NA (D)H dehydrogenase) genes were observed in both. Comparative analysis of the total cp genomes of P. storbatiana and P. wilsonii with those of other six related Phalaenopsis species confirmed the stable sequence identity for coding and non-coding regions and higher sequence variation in SC regions than IR regions. Most of their protein-coding genes had a high degree of codon preference. Moreover, 45 genes were discovered with significantly positive selection. However, different amplifications in IR regions were observed in these eight species. Phylogenetic analysis based on CDS from 60 species representing main clades in Orchidaceae indicated that Phalaenopsis species including P. stobartiana and P. wilsonii formed a monophyletic clade with high bootstrap nested in tribe Vandeae of Epidendroideae, which was consistent with those from previous studies.

CONCLUSIONS

The results could provide insight into understanding the plastome evolution and phylogenetic relationships of Phalaenopsis.

Comparative Analysis of Codon Usage Patterns in Nuclear and Chloroplast Genome of Dalbergia (Fabaceae)

The Dalbergia plants are widely distributed across more than 130 tropical and subtropical countries and have significant economic and medicinal value. Codon usage bias (CUB) is a critical feature for studying gene function and evolution, which can provide a better understanding of biological gene regulation. In this study, we comprehensively analyzed the CUB patterns of the nuclear genome, chloroplast genome, and gene expression, as well as systematic evolution of Dalbergia species. Our results showed that the synonymous and optimal codons in the coding regions of both nuclear and chloroplast genome of Dalbergia preferred ending with A/U at the third codon base. Natural selection was the primary factor affecting the CUB features. Furthermore, in highly expressed genes of Dalbergia odorifera, we found that genes with stronger CUB exhibited higher expression levels, and these highly expressed genes tended to favor the use of G/C-ending codons. In addition, the branching patterns of the protein-coding sequences and the chloroplast genome sequences were very similar in the systematic tree, and different with the cluster from the CUB of the chloroplast genome. This study highlights the CUB patterns and features of Dalbergia species in different genomes, explores the correlation between CUB preferences and gene expression, and further investigates the systematic evolution of Dalbergia, providing new insights into codon biology and the evolution of Dalbergia plants.

Analysis of Codon Usage Bias in Xyloglucan Endotransglycosylase (XET) Genes

Xyloglucan endotransglycosylase (XET) genes are widely distributed in most plants, but the codon usage bias of XET genes has remained uncharacterized. Thus, we analyzed the codon usage bias using 4500 codons of 20 XET genes to elucidate the genetic and evolutionary patterns. Phylogenetic and hierarchical cluster analyses revealed that the 20 XET genes belonged to two groups. The closer the genetic distance, the more similar the codon usage preference. The codon usage bias of most XET genes was weak, but there was also some codon usage bias. AGA, AGG, AUC, and GUG were the top four codons (RSCU > 1.5) in the 20 XET genes. CitXET had a stronger codon usage bias, and there were eight optimal codons of CitXET (i.e., AGA, AUU, UCU, CUU, CCA, GCU, GUU, and AAA). The RSCU values underwent a correspondence analysis. The two main factors affecting codon usage bias (i.e., Axes 1 and 2) accounted for 54.8% and 17.6% of the total variation, respectively. Multiple correspondence analysis revealed that XET genes were widely distributed, with Group 1 genes being closer to Axis 1 than Group 2 genes, which were closer to Axis 2. Codons with A/U at the third codon position were distributed closer to Axis 1 than codons with G/C at the third codon position. PgXET, ZmXET, VlXET, VrXET, and PcXET were biased toward codons ending with G/C. In contrast, CitXET, DpXET, and BrpXET were strongly biased toward codons ending with A/U, indicating that these XET genes have a strong codon usage bias. Translational selection and base composition (especially A and U at the third codon position), followed by mutation pressure and natural selection, may be the most important factors affecting codon usage of 20 XET genes. These results may be useful in clarifying the codon usage bias of XET genes and the relevant evolutionary characteristics.

Insights into Synonymous Codon Usage Bias in Hepatitis C Virus and Its Adaptation to Hosts

Hepatitis C virus (HCV) is enveloped RNA virus, encoding for a polyprotein that is processed by cellular proteases. The virus is responsible for liver cirrhosis, allograft rejection, and human hepatocellular carcinoma. Based on studies including compositional analysis, odds ratio analysis, parity analysis, skew analysis, relative synonymous codon usage, codon bias, and protein properties, it was evident that codon usage bias in HCV is dependent upon the nucleotide composition. Codon context analysis revealed CTC-CTG as a preferred codon pair. While CGA and CGT codons were rare, none of the codons were rare in HCV-like viruses envisaged in the present study. Many of the preferred codon pairs were valine amino acid-initiated, which possibly infers viral infectivity; hence the role of selection forces appears to act on the HCV genome, which was further validated by neutrality analysis where selection accounted for 87.28%, while mutation accounted for 12.72% force shaping codon usage. Furthermore, codon usage was correlated with the length of the genome. HCV viruses prefer valine-initiated codon pairs, while HCV-like viruses prefer alanine-initiated codon pairs. The HCV host range is very narrow and is confined to only humans and chimpanzees. Based on indices including codon usage correlation analysis, similarity index, and relative codon deoptimization index, it is evident in the study that the chimpanzee is the primary host of the virus. The present study helped elucidate the preferred host for HCV. The information presented in the study paved the way for generating an attenuated vaccine candidate through viral recoding, with finely tuned nucleotide composition and a perfect balance of preferred and rare codons.

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 Provide Insights into the Adaptation of Rice Genes under Stress Condition

Plants experience different stresses, i.e., abiotic, or biotic, and to combat them, plants re-program the expression of growth-, metabolism-, and resistance-related genes. These genes differ in their synonymous codon usage frequency and show codon usage bias. Here, we investigated the correlation among codon usage bias, gene expression, and underlying mechanisms in rice under abiotic and biotic stress conditions. The results indicated that genes with higher expression (up- or downregulated) levels had high GC content (≥60%), a low effective number of codon usage (≤40), and exhibited strong biases towards the codons with C/G at the third nucleotide position, irrespective of stress received. TTC, ATC, and CTC were the most preferred codons, while TAC, CAC, AAC, GAC, and TGC were moderately preferred under any stress (abiotic or biotic) condition. Additionally, downregulated genes are under mutational pressure (R² ≥ 0.5) while upregulated genes are under natural selection pressure (R² ≤ 0.5). Based on these results, we also identified the possible target codons that can be used to design an optimized set of genes with specific codons to develop climate-resilient varieties. Conclusively, under stress, rice has a bias towards codon usage which is correlated with GC content, gene expression level, and gene length.