Phylogenomics and plastomics offer new evolutionary perspectives on Kalanchoideae (Crassulaceae).

BACKGROUND AND AIMS: Kalanchoideae is one of three subfamilies within Crassulaceae and contains four genera. Despite previous efforts, the phylogeny of Kalanchoideae remains inadequately resolved with persistent issues including low support, unstructured topologies and polytomies. This study aimed to address two central objectives: (1) resolving the pending phylogenetic questions within Kalanchoideae by using organelle-scale 'barcodes' (plastomes) and nuclear data; and (2) investigating interspecific diversity patterns among Kalanchoideae plastomes. METHODS: To explore the plastome evolution in Kalanchoideae, we newly sequenced 38 plastomes representing all four constituent genera (Adromischus, Cotyledon, Kalanchoe and Tylecodon). We performed comparative analyses of plastomic features, including GC and gene contents, gene distributions at the IR (inverted repeat) boundaries, nucleotide divergence, plastomic tRNA (pttRNA) structures and codon aversions. Additionally, phylogenetic inferences were inferred using both the plastomic dataset (79 genes) and nuclear dataset (1054 genes). KEY RESULTS: Significant heterogeneities were observed in plastome lengths among Kalanchoideae, strongly correlated with LSC (large single copy) lengths. Informative diversities existed in the gene content at SSC/IRa (small single copy/inverted repeat a), with unique patterns individually identified in Adromischus leucophyllus and one major Kalanchoe clade. The ycf1 gene was assessed as a shared hypervariable region among all four genera, containing nine lineage-specific indels. Three pttRNAs exhibited unique structures specific to Kalanchoideae and the genera Adromischus and Kalanchoe. Moreover, 24 coding sequences revealed a total of 41 lineage-specific unused codons across all four constituent genera. The phyloplastomic inferences clearly depicted internal branching patterns in Kalanchoideae. Most notably, by both plastid- and nuclear-based phylogenies, our research offers the first evidence that Kalanchoe section Eukalanchoe is not monophyletic. CONCLUSIONS: This study conducted comprehensive analyses on 38 newly reported Kalanchoideae plastomes. Importantly, our results not only reconstructed well-resolved phylogenies within Kalanchoideae, but also identified highly informative unique markers at the subfamily, genus and species levels. These findings significantly enhance our understanding of the evolutionary history of Kalanchoideae.

Comparative genomics of the medicinal plants Lonicera macranthoides and L. japonica provides insight into genus genome evolution and hederagenin-based saponin biosynthesis.

Lonicera macranthoides (LM) and L. japonica (LJ) are medicinal plants widely used in treating viral diseases, such as COVID-19. Although the two species are morphologically similar, their secondary metabolite profiles are significantly different. Here, metabolomics analysis showed that LM contained ~86.01 mg/g hederagenin-based saponins, 2000-fold higher than LJ. To gain molecular insights into its secondary metabolite production, a chromosome-level genome of LM was constructed, comprising 9 pseudo-chromosomes with 40 097 protein-encoding genes. Genome evolution analysis showed that LM and LJ were diverged 1.30-2.27 million years ago (MYA). The two plant species experienced a common whole-genome duplication event that occurred ∼53.9-55.2 MYA before speciation. Genes involved in hederagenin-based saponin biosynthesis were arranged in clusters on the chromosomes of LM and they were more highly expressed in LM than in LJ. Among them, oleanolic acid synthase (OAS) and UDP-glycosyltransferase 73 (UGT73) families were much more highly expressed in LM than in LJ. Specifically, LmOAS1 was identified to effectively catalyse the C-28 oxidation of ß-Amyrin to form oleanolic acid, the precursor of hederagenin-based saponin. LmUGT73P1 was identified to catalyse cauloside A to produce α-hederin. We further identified the key amino acid residues of LmOAS1 and LmUGT73P1 for their enzymatic activities. Additionally, comparing with collinear genes in LJ, LmOAS1 and LmUGT73P1 had an interesting phenomenon of 'neighbourhood replication' in LM genome. Collectively, the genomic resource and candidate genes reported here set the foundation to fully reveal the genome evolution of the Lonicera genus and hederagenin-based saponin biosynthetic pathway.

Plastome evolution of Aeonium and Monanthes (Crassulaceae): insights into the variation of plastomic tRNAs, and the patterns of codon usage and aversion.

MAIN CONCLUSION: This study reported 13 new plastomes from Aeonium and Monanthes, and observed new markers for phylogeny and DNA barcoding, such as novel tRNA structures and codon usage bias and aversion. The Macaronesian clade of Crassulaceae consists of three genera: Aichryson, with about 15 species; Monanthes, with about 10 species; Aeonium, with about 40 species. Within this clade, Aeonium, known as "the botanical equivalent of Darwin's finches", is regarded as an excellent model plant for researching adaptive evolution. Differing from the well-resolved relationships among three genera of the Macaronesian clade, the internal branching patterns within the genus Aeonium are largely unclear. In this study, we first reported 13 new plastomes from genus Aeonium and the closely related genus Monanthes. We further performed comprehensive analyses of the plastomes, with focuses on the secondary structures of pttRNAs and the patterns of codon usage and aversion. With a typical circular and quadripartite structure, the 13 plastomes ranged from 149,900 to 151,030 bp in size, and the unique pattern in IR junctions might become a family-specific marker for Crassulaceae species. Surprisingly, the π values of plastomes from Monanthes were almost twice those from Aeonium. Most importantly, we strongly recommend that highly polymorphic regions, novel putative pttRNA structures, patterns of codon usage bias and aversion derived from plastomes might have phylogenetic implications, and could act as new markers for DNA barcoding of plants. The results of phylogenetic analyses strongly supported a clear internal branching pattern in Macaronesian clade (represented by Aeonium and Monanthes), with higher nodal support values. The findings reported here will provide new insights into the variation of pttRNAs, and the patterns of codon usage and aversion of the family Crassulaceae.

Plastomes of Bletilla (Orchidaceae) and Phylogenetic Implications.

The genus Bletilla is a small genus of only five species distributed across Asia, including B. chartacea, B. foliosa, B. formosana, B. ochracea and B. striata, which is of great medicinal importance. Furthermore, this genus is a member of the key tribe Arethuseae (Orchidaceae), harboring an extremely complicated taxonomic history. Recently, the monophyletic status of Bletilla has been challenged, and the phylogenetic relationships within this genus are still unclear. The plastome, which is rich in both sequence and structural variation, has emerged as a powerful tool for understanding plant evolution. Along with four new plastomes, this work is committed to exploring plastomic markers to elucidate the phylogeny of Bletilla. Our results reveal considerable plastomic differences between B. sinensis and the other three taxa in many aspects. Most importantly, the specific features of the IR junction patterns, novel pttRNA structures and codon aversion motifs can serve as useful molecular markers for Bletilla phylogeny. Moreover, based on maximum likelihood and Bayesian inference methods, our phylogenetic analyses based on two datasets of Arethuseae strongly imply that Bletilla is non-monophyletic. Accordingly, our findings from this study provide novel potential markers for species identification, and shed light on the evolution of Bletilla and Arethuseae.

Identification and characterization of the SET domain gene family in maize.

Histone lysine methylation plays a pivotal role in a variety of developmental and physiological processes through modifying chromatin structure and thereby regulating eukaryotic gene transcription. The SET domain proteins represent putative candidates for lysine methyltransferases containing the evolutionarily-conserved SET domain, and important epigenetic regulators present in eukaryotes. In recent years, increasing evidence reveals that SET domain proteins are encoded by a large multigene family in plants and investigation of the SET domain gene family will serve to elucidate the epigenetic mechanism diversity in plants. Although the SET domain gene family has been thoroughly characterized in multiple plant species including two model plant systems, Arabidopsis and rice, through their sequenced genomes, analysis of the entire SET domain gene family in maize was not completed following maize (B73) genome sequencing project. Here, we performed a genome-wide structural and evolutionary analysis of maize SET domain genes from the latest version of the maize (B73) genome. A complete set of 43 SET domain genes (Zmset1-43) were identified in the maize genome using Blast search tools and categorized into seven classes (Class I-VII) based on phylogeny. Chromosomal location of these genes revealed that they are unevenly distributed on all ten chromosomes with seven segmental duplication events, suggesting that segmental duplication played a key role in expansion of the maize SET domain gene family. EST expression data mining revealed that these newly identified genes had temporal and spatial expression pattern and suggested that many maize SET domain genes play functional developmental roles in multiple tissues. Furthermore, the transcripts of the 18 genes (the Class V subfamily) were detected in the leaves by two different abiotic stress treatments using semi-quantitative RT-PCR. The data demonstrated that these genes exhibited different expression levels in stress treatments. Overall, our study will serve to better understand the complexity of the maize SET domain gene family and also be beneficial for future experimental research to further unravel the mechanisms of epigenetic regulation in plants.

Intraspecific and Intrageneric Genomic Variation across Three Sedum Species (Crassulaceae): A Plastomic Perspective.

Sedum is the largest succulent genus in Crassulaceae. Because of predominant maternal inheritance, little recombination, and slow evolution, plastomes can serve as powerful super barcodes for inter- or intra-species phylogenetic analyses. While previous research has focused on plastomes between Sedum species, intra-species studies are scarce. Here, we sequenced plastomes from three Sedum species (Sedum alfredii, Sedum plumbizincicola, and Sedum japonicum) to understand their evolutionary relationships and plastome structural evolution. Our analyses revealed minimal size and GC content variation across species. However, gene distribution at IR boundaries, repeat structures, and codon usage patterns showed diversity at both inter-specific and intra-specific levels. Notably, an rps19 gene expansion and a bias toward A/T-ending codons were observed. Codon aversion motifs also varied, potentially serving as markers for future studies. Phylogenetic analyses confirmed the non-monophyly of Sedum and divided the Acre clade into two groups. Individuals from the same species clustered together, with strong support for the relationships between S. alfredii, S. tricarpum, and S. plumbizincicola. Additionally, S. japonicum clearly affiliates with the Acre clade. This study provides valuable insights into both intra-specific and intra-generic plastome variation in Sedum, as well as overall plastome evolution within the genus.

Codon Usage Analyses Reveal the Evolutionary Patterns among Plastid Genes of Saxifragales at a Larger-Sampling Scale.

Saxifragales is a 15-family order of early-divergent Eudicots with a rich morphological diversity and an ancient rapid radiation. Codon usage bias (CUB) analyses have emerged as an essential tool for understanding the evolutionary dynamics in genes. Thus far, the codon utilization patterns had only been reported in four separate genera within Saxifragales. This study provides a comprehensive assessment of the codon manipulation based on 50 plastid genes, covering 11 constituent families at a larger sampling scale. Our results first showed a high preference for AT bases and AT-ending codons. We then used effective number of codons (ENC) to assess a range of codon bias levels in the plastid genes. We also detected high-informative intrafamilial differences of ENC in three families. Subsequently, parity rule 2 (PR2) plot analyses revealed both family-unique and order-shared bias patterns. Most importantly, the ENC plots and neutrality analyses collectively supported the dominant roles of selection in the CUB of Saxifragales plastid genes. Notably, the phylogenetic affinities inferred by both ML and BI methods were consistent with each other, and they all comprised two primary clades and four subclades. These findings significantly enhance our understanding of the evolutionary processes of the Saxifrage order, and could potentially inspire more CUB analyses at higher taxonomic levels.

Genome evolution of Buchnera aphidicola (Gammaproteobacteria): Insights into strand compositional asymmetry, codon usage bias, and phylogenetic implications.

Taxa of Buchnera aphidicola (hereafter "Buchnera") are mutualistic intracellular symbionts of aphids, known for their remarkable biological traits such as genome reduction, strand compositional asymmetry, and symbiont-host coevolution. With the growing availability of genomic data, we performed a comprehensive analysis of 103 genomes of Buchnera strains from 12 host subfamilies, focusing on the genomic characterizations, codon usage patterns, and phylogenetic implications. Our findings revealed consistent features among all genomes, including small genome sizes, low GC contents, and gene losses. We also identified strong strand compositional asymmetries in all strains at the genome level. Further investigation suggested that mutation pressure may have played a crucial role in shaping codon usage of Buchnera. Moreover, the genomic asymmetries were reflected in asymmetric codon usage preferences within chromosomal genes. Notably, the levels of these asymmetries were varied among strains and were significantly influenced by the degrees of genome shrinkages. Lastly, our phylogenetic analyses presented an alternative topology of Aphididae, based on the Buchnera symbionts, providing robust confirmation of the paraphylies of Eriosomatinae, and Macrosiphini. Our objectives are to further understand the strand compositional asymmetry and codon usage bias of Buchnera taxa, and provide new perspectives for phylogenetic studies of Aphididae.

The mitochondrial genome of the Cinnamon Bittern, Ixobrychus cinnamomeus (Pelecaniformes: Ardeidae): sequence, structure and phylogenetic analysis.

Ixobrychus cinnamomeus is a member of the large wading bird family, known as Ardeidae. In the present study, we determined the complete mitochondrial genome of I. cinnamomeus for use in future phylogenetic analysis. This circular mitochondrial genome is 17,180 bp in length and composed of 13 protein-coding genes, 22 tRNA genes, two rRNA genes and one putative control region. Three conserved domains and a minisatellite of 17 nucleotides with 22 tandem repeats were detected at the end of the control region. Phylogenetic relationships were reconstructed using the nucleotide and corresponding amino acid datasets of 12 concatenated protein-coding genes from the mitochondrial genome. Using maximum likelihood, maximum parsimony and Bayesian inference methods, the monophyly of Ciconiidae, Ardeidae and Threskiornithidae were confirmed; however, the monophyly of traditional Ciconiiformes and Pelecaniformes failed to be recovered. Although further studies are recommended to clarify relationships among and within the orders of Ciconiiformes, Pelecaniformes, Suliformes and Phaethontiformes, our results provide preliminary exploratory results that can be useful in the current understanding of avian phylogenetics.

Genome-Wide Characterization of Sedum plumbizincicola HMA Gene Family Provides Functional Implications in Cadmium Response.

Heavy-metal ATPase (HMA), an ancient family of transition metal pumps, plays important roles in the transmembrane transport of transition metals such as Cu, Zn, Cd, and Co. Although characterization of HMAs has been conducted in several plants, scarcely knowledge was revealed in Sedum plumbizincicola, a type of cadmium (Cd) hyperaccumulator found in Zhejiang, China. In this study, we first carried out research on genome-wide analysis of the HMA gene family in S. plumbizincicola and finally identified 8 SpHMA genes and divided them into two subfamilies according to sequence alignment and phylogenetic analysis. In addition, a structural analysis showed that SpHMAs were relatively conserved during evolution. All of the SpHMAs contained the HMA domain and the highly conserved motifs, such as DKTGT, GDGxNDxP, PxxK S/TGE, HP, and CPx/SPC. A promoter analysis showed that the majority of the SpHMA genes had cis-acting elements related to the abiotic stress response. The expression profiles showed that most SpHMAs exhibited tissue expression specificity and their expression can be regulated by different heavy metal stress. The members of Zn/Co/Cd/Pb subgroup (SpHMA1-3) were verified to be upregulated in various tissues when exposed to CdCl2. Here we also found that the expression of SpHMA7, which belonged to the Cu/Ag subgroup, had an upregulated trend in Cd stress. Overexpression of SpHMA7 in transgenic yeast indicated an improved sensitivity to Cd. These results provide insights into the evolutionary processes and potential functions of the HMA gene family in S. plumbizincicola, laying a theoretical basis for further studies on figuring out their roles in regulating plant responses to biotic/abiotic stresses.

Mitogenomic Codon Usage Patterns of Superfamily Certhioidea (Aves, Passeriformes): Insights into Asymmetrical Bias and Phylogenetic Implications.

The superfamily Certhioidea currently comprises five families. Due to the rapid diversification, the phylogeny of Certhioidea is still controversial. The advent of next generation sequencing provides a unique opportunity for a mitogenome-wide study. Here, we first provided six new complete mitogenomes of Certhioidea (Certhia americana, C. familiaris, Salpornis spilonota, Cantorchilus leucotis, Pheugopedius coraya, and Pheugopedius genibarbis). We further paid attention to the genomic characteristics, codon usages, evolutionary rates, and phylogeny of the Certhioidea mitogenomes. All mitogenomes we analyzed displayed typical ancestral avian gene order with 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and one control region (CR). Our study indicated the strand-biased compositional asymmetry might shape codon usage preferences in mitochondrial genes. In addition, natural selection might be the main factor in shaping the codon usages of genes. Additionally, evolutionary rate analyses indicated all mitochondrial genes were under purifying selection. Moreover, MT-ATP8 and MT-CO1 were the most rapidly evolving gene and conserved genes, respectively. According to our mitophylogenetic analyses, the monophylies of Troglodytidae and Sittidae were strongly supported. Importantly, we suggest that Salpornis should be separated from Certhiidae and put into Salpornithidae to maintain the monophyly of Certhiidae. Our findings are useful for further evolutionary studies within Certhioidea.

The Mitogenome of Sedum plumbizincicola (Crassulaceae): Insights into RNA Editing, Lateral Gene Transfer, and Phylogenetic Implications.

As the largest family within the order Saxifragales, Crassulaceae contains about 34 genera with 1400 species. Mitochondria play a critical role in cellular energy production. Since the first land plant mitogenome was reported in Arabidopsis, more than 400 mitogenomic sequences have been deposited in a public database. However, no entire mitogenome data have been available for species of Crassulaceae to date. To better understand the evolutionary history of the organelles of Crassulaceae, we sequenced and performed comprehensive analyses on the mitogenome of Sedum plumbizincicola. The master mitogenomic circle is 212,159 bp in length, including 31 protein-coding genes (PCGs), 14 tRNA genes, and 3 rRNA genes. We further identified totally 508 RNA editing sites in PCGs, and demonstrated that the second codon positions of mitochondrial genes are most prone to RNA editing events. Notably, by neutrality plot analyses, we observed that the mitochondrial RNA editing events have large effects on the driving forces of plant evolution. Additionally, 4 MTPTs and 686 NUMTs were detected in the mitochondrial and nuclear genomes of S. plumbizincicola, respectively. Additionally, we conducted further analyses on gene transfer, secondary structures of mitochondrial RNAs, and phylogenetic implications. Therefore, the findings presented here will be helpful for future investigations on plant mitogenomes.

Ten Plastomes of Crassula (Crassulaceae) and Phylogenetic Implications.

The genus Crassula is the second-largest genus in the family Crassulaceae, with about 200 species. As an acknowledged super-barcode, plastomes have been extensively utilized for plant evolutionary studies. Here, we first report 10 new plastomes of Crassula. We further focused on the structural characterizations, codon usage, aversion patterns, and evolutionary rates of plastomes. The IR junction patterns-IRb had 110 bp expansion to rps19-were conservative among Crassula species. Interestingly, we found the codon usage patterns of matK gene in Crassula species are unique among Crassulaceae species with elevated ENC values. Furthermore, subgenus Crassula species have specific GC-biases in the matK gene. In addition, the codon aversion motifs from matK, pafI, and rpl22 contained phylogenetic implications within Crassula. The evolutionary rates analyses indicated all plastid genes of Crassulaceae were under the purifying selection. Among plastid genes, ycf1 and ycf2 were the most rapidly evolving genes, whereas psaC was the most conserved gene. Additionally, our phylogenetic analyses strongly supported that Crassula is sister to all other Crassulaceae species. Our findings will be useful for further evolutionary studies within the Crassula and Crassulaceae.

Structural Diversities and Phylogenetic Signals in Plastomes of the Early-Divergent Angiosperms: A Case Study in Saxifragales.

As representative of the early-divergent groups of angiosperms, Saxifragales is extremely divergent in morphology, comprising 15 families. Within this order, our previous case studies observed significant structural diversities among the plastomes of several lineages, suggesting a possible role in elucidating their deep phylogenetic relationships. Here, we collected 208 available plastomes from 11 constituent families to explore the evolutionary patterns among Saxifragales. With thorough comparisons, the losses of two genes and three introns were found in several groups. Notably, 432 indel events have been observed from the introns of all 17 plastomic intron-containing genes, which could well play an important role in family barcoding. Moreover, numerous heterogeneities and strong intrafamilial phylogenetic implications were revealed in pttRNA (plastomic tRNA) structures, and the unique structural patterns were also determined for five families. Most importantly, based on the well-supported phylogenetic trees, evident phylogenetic signals were detected in combinations with the identified pttRNAs features and intron indels, demonstrating abundant lineage-specific characteristics for Saxifragales. Collectively, the results reported here could not only provide a deeper understanding into the evolutionary patterns of Saxifragales, but also provide a case study for exploring the plastome evolution at a high taxonomic level of angiosperms.

Codon usage patterns and evolution of HSP60 in birds.

Heat shock protein 60 (HSP60) is highly conserved from prokaryotic to eukaryotic organisms, acting as molecular chaperone and other vital biological functions. In spite of increasing knowledge of HSP60, its evolutionary mechanism on functional adaption is still far from completely understood. Moreover, analysis of codon usage bias (CUB) is a powerful tool to understand evolutionary association studies. However, so far, as we know, no scientific work on CUB of HSP60 in birds has been reported. In this study, we provide a comprehensive analysis on the codon usage and molecular evolution of HSP60 across birds. The results indicated that HSP60 had a weak codon usage bias with high ENC values (range from 52.66 to 61), low RSCU, and A/T-ending codons were mostly preferred. Meanwhile, it was considered that mutation, natural selection, and genetic drift combined to shape codon usage patterns with different strength proportions among various birds for HSP60. Then, the LRT tests suggested that different lineages of birds might be under similar selective pressures. Besides, the two positive selection sites (151 and 131) were detected and might undergo radical changes. These findings would contribute to understand function diversity and molecular evolution of HSP60 in birds.

Quantification and evolution of mitochondrial genome rearrangement in Amphibians.

BACKGROUND: Rearrangement is an important topic in the research of amphibian mitochondrial genomes ("mitogenomes" hereafter), whose causes and mechanisms remain enigmatic. Globally examining mitogenome rearrangements and uncovering their characteristics can contribute to a better understanding of mitogenome evolution. RESULTS: Here we systematically investigated mitogenome arrangements of 232 amphibians including four newly sequenced Dicroglossidae mitogenomes. The results showed that our new sequenced mitogenomes all possessed a trnM tandem duplication, which was not exclusive to Dicroglossidae. By merging the same arrangements, the mitogenomes of ~ 80% species belonged to the four major patterns, the major two of which were typical vertebrate arrangement and typical neobatrachian arrangement. Using qMGR for calculating rearrangement frequency (RF) (%), we found that the control region (CR) (RF = 45.04) and trnL2 (RF = 38.79) were the two most frequently rearranged components. Forty-seven point eight percentage of amphibians possessed rearranged mitogenomes including all neobatrachians and their distribution was significantly clustered in the phylogenetic trees (p < 0.001). In addition, we argued that the typical neobatrachian arrangement may have appeared in the Late Jurassic according to possible occurrence time estimation. CONCLUSION: It was the first global census of amphibian mitogenome arrangements from the perspective of quantity statistics, which helped us to systematically understand the type, distribution, frequency and phylogenetic characteristics of these rearrangements.

qMGR: A new approach for quantifying mitochondrial genome rearrangement.

Rearrangement is one of the most studied features in the animal mitochondrial genomes. The progress in high-throughput sequencing and comparative genomics has brought opportunities for systematic studies of mitochondrial genome rearrangements. However, there are few reports on globally examining mitogenome rearrangement and distinguishing the rearrangement frequency of each gene, which could contribute to a better understanding of its models and evolution. We presented qMGR, a new approach for large-scale quantifying mitogenome rearrangements considering a single gene as a structural unit. Compared to a reference arrangement, qMGR accumulates the changes of two nearest neighbor genes to calculate rearrangement score (RS) and rearrangement frequency (RF) of each single gene in the mitogenomes of a given taxonomic group. By accumulating RS of all genes in one genome, qMGR was developed to calculate each mitogenome rearrangement score, which can be used as a quantitative feature of the mitogenome rearrangement. Based on the frequency of rearrangement of each gene, qMGR can further detect the conserved gene set and high frequency rearrangement segments within the taxon. They may facilitate the assessment of rearrangement distances and understanding rearrangement mechanisms. qMGR web service is freely available at http://qmgr.hnnu.edu.cn/. The source code is available under GNU GPL at https://github.com/zhanglab2019/qMGR.

Systematic Identification and Evolution Analysis of Sox Genes in Coturnix japonica Based on Comparative Genomics.

Coturnix japonica (Japanese quail) has been extensively used as a model animal for biological studies. The Sox gene family, which was systematically characterized by a high-mobility group (HMG-box) in many animal species, encodes transcription factors that play central roles during multiple developmental processes. However, genome-wide investigations on the Sox gene family in birds are scarce. In the current study, we first performed a genome-wide study to explore the Sox gene family in galliform birds. Based on available genomic sequences retrieved from the NCBI database, we focused on the global identification of the Sox gene family in C. japonica and other species in Galliformes, and the evolutionary relationships of Sox genes. In our result, a total of 35 Sox genes in seven groups were identified in the C. japonica genome. Our results also revealed that dispersed gene duplications contributed the most to the expansion of the Sox gene family in Galliform birds. Evolutionary analyses indicated that Sox genes are an ancient gene family, and strong purifying selections played key roles in the evolution of CjSox genes of C. japonica. More interestingly, we observed that most Sox genes exhibited highly embryo-specific expression in both gonads. Our findings provided new insights into the molecular function and phylogeny of Sox gene family in birds.

Next-Generation Genome Sequencing of Sedum plumbizincicola Sheds Light on the Structural Evolution of Plastid rRNA Operon and Phylogenetic Implications within Saxifragales.

The genus Sedum, with about 470 recognized species, is classified in the family Crassulaceae of the order Saxifragales. Phylogenetic relationships within the Saxifragales are still unresolved and controversial. In this study, the plastome of S. plumbizincicola was firstly presented, with a focus on the structural analysis of rrn operon and phylogenetic implications within the order Saxifragaceae. The assembled complete plastome of S. plumbizincicola is 149,397 bp in size, with a typical circular, double-stranded, and quadripartite structure of angiosperms. It contains 133 genes, including 85 protein-coding genes (PCGs), 36 tRNA genes, 8 rRNA genes, and four pseudogenes (one ycf1, one rps19, and two ycf15). The predicted secondary structure of S. plumbizincicola 16S rRNA includes three main domains organized in 74 helices. Further, our results confirm that 4.5S rRNA of higher plants is associated with fragmentation of 23S rRNA progenitor. Notably, we also found the sequence of putative rrn5 promoter has some evolutionary implications within the order Saxifragales. Moreover, our phylogenetic analyses suggested that S. plumbizincicola had a closer relationship with S. sarmentosum than S. oryzifolium, and supported the taxonomic revision of Phedimus. Our findings of the present study will be useful for further investigation of the evolution of plastid rRNA operon and phylogenetic relationships within Saxifragales.

Two new mitogenomes of Picidae (Aves, Piciformes): Sequence, structure and phylogenetic analyses.

The family Picidae is classified in the order Piciformes with 236 recognized species in 35 genera. Phylogenetic relationships within the Piciformes are still unresolved by major cause of plumage convergence. This study presented two new mitogenomes of Picidae, Darjeeling woodpecker (Dendrocopos darjellensis) and Gray-capped woodpecker (Yungipicus canicapillus), with the size of 16,727 and 16,847 bp, respectively. They have the identical gene order: 37 genes, including 13 PCGs, two rRNA genes, 22 tRNA genes, and two control regions. Furthermore, an extra cytosine insertion at position 174 of MT-ND3 was also found in both species. The MT-RNR1 of Y. canicapillus shared 89.0% nucleotide sequence identity and a similar secondary structure with that of D. darjellensis, consisting of 46 helices and three main domains. There is more divergence in the MT-RNR2 secondary structures than those of MT-RNR1 between the two species. We found the highest dN/dS for the MT-ATP8 (0.08326) among Piciformes, while the lowest for the MT-CO1 (0.00802). Our phylogenetic analyses suggested that the subfamily Picumninae is paraphyletic, and D. darjellensis had a closer relationship with D. major than D. leucotos. The findings of the present study will be useful for further investigating the evolutionary relationships within Piciformes.