scholarly journals Tracing the evolution of the plastome and mitogenome in the Chloropicophyceae uncovered convergent tRNA gene losses and a variant plastid genetic code

2019 ◽  
Author(s):  
Monique Turmel ◽  
Adriana Lopes dos Santos ◽  
Christian Otis ◽  
Roxanne Sergerie ◽  
Claude Lemieux
Keyword(s):  
Genetic Code ◽  
Trna Gene ◽  
Marine Phytoplankton ◽  
Trna Genes ◽  
Protein Coding ◽  
Organelle Genomes ◽  
Phytoplankton Communities ◽  
Plastid Protein ◽  
Intergenic Regions ◽  
Phylogenetic Affinities

AbstractThe tiny green algae belonging to the Chloropicophyceae play a key role in marine phytoplankton communities; this newly erected class of prasinophytes comprises two genera (Chloropicon and Chloroparvula) containing each several species. We sequenced the plastomes and mitogenomes of eight Chloropicon and five Chloroparvula species to better delineate the phylogenetic affinities of these taxa and to infer the suite of changes that their organelle genomes sustained during evolution. The relationships resolved in organelle-based phylogenomic trees were essentially congruent with previously reported rRNA trees, and similar evolutionary trends but distinct dynamics were identified for the plastome and mitogenome. Although the plastome sustained considerable changes in gene content and order at the time the two genera split, subsequently it remained stable and maintained a very small size. The mitogenome, however, was remodeled more gradually and showed more fluctuation in size, mainly as a result of expansions/contractions of intergenic regions. Remarkably, the plastome and mitogenome lost a common set of three tRNA genes, with the trnI(cau) and trnL(uaa) losses being accompanied with important variations in codon usage. Unexpectedly, despite the disappearance of trnI(cau) from the plastome in the Chloroparvula lineage, AUA codons (the codons recognized by this gene product) were detected in certain plastid genes. By comparing the sequences of plastid protein-coding genes from chloropicophycean and phylogenetically diverse chlorophyte algae with those of the corresponding predicted proteins, we discovered that the AUA codon was reassigned from isoleucine to methionine in Chloroparvula. This noncanonical genetic code has not previously been uncovered in plastids.

scholarly journals Complete mitochondrial genome of Iniistius trivittatus and unique variation in two observed inserts between rRNA and tRNA genes in wrasses

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Dong Liu ◽  
Yuanyuan Zhang ◽  
Ming Zhang ◽  
Jinquan Yang ◽  
Wenqiao Tang
Keyword(s):  
Mitochondrial Genome ◽  
Phylogenetic Trees ◽  
Morphological Evolution ◽  
Complete Mitochondrial Genome ◽  
Rrna Genes ◽  
12S Rrna ◽  
Trna Genes ◽  
Protein Coding ◽  
Jaw Apparatus ◽  
Intergenic Regions

Abstract Background The family Labridae made up of 519 species in the world. The functional evolution of the feeding-related jaws leaded to differentiation of species, and the pharyngeal jaw apparatus evolved independently, but evolutionary mechanism still remain unaddressed in wrasses. Mitogenomes data can be used to infer genetic diversification and investigate evolutionary history of wrasses, whereas only eight complete mitogenomes in this family have been sequenced to date. Here, we sequenced the complete mitogenomes of Iniistius trivittatus to investigate genetic differentiation among wrasse species. Results We sequenced the complete mitogenomes of I. trivittatus using a novel PCR strategy. The I. trivittatus mitogenomes is 16,820 bp in length and includes 13 protein -coding genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a control region. Compared to eight known mitochondrial genome, 2 additional noncoding regions (lengths of 121 and 107 bp), or so-called inserts, are found in the intergenic regions 12S rRNA - tRNAVal - 16S rRNA. The presumed origin of the two rare inserts is from tRNA- related retrotransposons. Compared with cytochrome b gene, the two insert sequences are highly conserved at the intraspecies level, but they showed significant variation and low similarity (< 70%) at the interspecies level. The insert events were only observed in I. trivittatus by checking the phylogenetic trees based on the complete mitogenomes of Labrida species. This finding provides evidence that in the mitogenomes, retrotransposon inserts result in intraspecific homoplasmy and interspecific heteroplasmy by natural selection and adaptation to various environments. Conclusions This study found additional mitogenome inserts limited in wrasse species. The rRNA genes with inserts might have experienced a selective pressure for adaptation to feeding modes. Such knowledge can enable a better understanding of molecular mechanism underlying morphological evolution in wrasses.

The mitochondrial genome of Gyrodactylus salaris (Platyhelminthes: Monogenea), a pathogen of Atlantic salmon (Salmo salar)

Parasitology ◽  
2006 ◽  
Vol 134 (5) ◽  
pp. 739-747 ◽  
Author(s):  
T. HUYSE ◽  
L. PLAISANCE ◽  
B. L. WEBSTER ◽  
T. A. MO ◽  
T. A. BAKKE ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Ribosomal Rna ◽  
Trna Gene ◽  
Rrna Genes ◽  
Gene Arrangement ◽  
Mitochondrial Genomes ◽  
Trna Genes ◽  
Protein Coding ◽  
Coding Regions ◽  
Mt Genome

SUMMARYIn the present study, we describe the complete mitochondrial (mt) genome of the Atlantic salmon parasite Gyrodactylus salaris, the first for any monogenean species. The circular genome is 14 790 bp in size. All of the 35 genes recognized from other flatworm mitochondrial genomes were identified, and they are transcribed from the same strand. The protein-coding and ribosomal RNA (rRNA) genes share the same gene arrangement as those published previously for neodermatan mt genomes (representing cestodes and digeneans only), and the genome has an overall A+T content of 65%. Three transfer RNA (tRNA) genes overlap with other genes, whereas the secondary structure of 3 tRNA genes lack the DHU arm and 1 tRNA gene lacks the TΨC arm. Eighteen regions of non-coding DNA ranging from 4 to 112 bp in length, totalling 278 bp, were identified as well as 2 large non-coding regions (799 bp and 768 bp) that were almost identical to each other. The completion of the mt genome offers the opportunity of defining new molecular markers for studying evolutionary relationships within and among gyrodactylid species.

scholarly journals The Repertoire of Transfer RNA Genes Is Tuned to Codon Usage Bias in the Genomes of Phytophthora sojae and Phytophthora ramorum

2006 ◽  
Vol 19 (12) ◽  
pp. 1322-1328 ◽  
Author(s):  
Sucheta Tripathy ◽  
Brett M. Tyler
Keyword(s):  
Amino Acid ◽  
Codon Usage ◽  
Trna Gene ◽  
Phytophthora Sojae ◽  
Phytophthora Ramorum ◽  
Trna Genes ◽  
Strongly Correlated ◽  
Gene Frequencies ◽  
Protein Coding ◽  
Rna Genes

In all, 238 and 155 transfer (t)RNA genes were predicted from the genomes of Phytophthora sojae and P. ramorum, respectively. After omitting pseudogenes and undetermined types of tRNA genes, there remained 208 P. sojae tRNA genes and 140 P. ramorum tRNA genes. There were 45 types of tRNA genes, with distinct anticodons, in each species. Fourteen common anticodon types of tRNAs are missing altogether from the genome in the two species; however, these appear to be compensated by wobbling of other tRNA anticodons in a manner which is tied to the codon bias in Phytophthora genes. The most abundant tRNA class was arginine in both P. sojae and P. ramorum. A codon usage table was generated for these two organisms from a total of 9,803,525 codons in P. sojae and 7,496,598 codons in P. ramorum. The most abundant codon type detected from the codon usage tables was GAG (encoding glutamic acid), whereas the most numerous tRNA gene had a me-thionine anticodon (CAT). The correlation between the frequencies of tRNA genes and the codon frequencies in protein-coding genes was very low (0.12 in P. sojae and 0.19 in P. ramorum); however, the correlation between amino acid tRNA gene frequency and the corresponding amino acid codon frequency in P. sojae and P. ramorum was substantially higher (0.53 in P. sojae and 0.77 in P. ramorum). The codon usage frequencies of P. sojae and P. ramorum were very strongly correlated (0.99), as were tRNA gene frequencies (0.77). Approximately 60% of orthologous tRNA gene pairs in P. sojae and P. ramorum are located in regions that have conserved synteny in the two species.

scholarly journals Analyzing and Characterizing the Chloroplast Genome of Salix wilsonii

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Yingnan Chen ◽  
Nan Hu ◽  
Huaitong Wu
Keyword(s):  
Chloroplast Genome ◽  
Tandem Repeats ◽  
Single Copy ◽  
Rrna Genes ◽  
Whole Genome Sequencing Data ◽  
Trna Genes ◽  
Sequencing Data ◽  
Protein Coding ◽  
Organelle Genomes ◽  
Additional Sequence

Salix wilsonii is an important ornamental willow tree widely distributed in China. In this study, an integrated circular chloroplast genome was reconstructed for S. wilsonii based on the chloroplast reads screened from the whole-genome sequencing data generated with the PacBio RSII platform. The obtained pseudomolecule was 155,750 bp long and had a typical quadripartite structure, comprising a large single copy region (LSC, 84,638 bp) and a small single copy region (SSC, 16,282 bp) separated by two inverted repeat regions (IR, 27,415 bp). The S. wilsonii chloroplast genome encoded 115 unique genes, including four rRNA genes, 30 tRNA genes, 78 protein-coding genes, and three pseudogenes. Repetitive sequence analysis identified 32 tandem repeats, 22 forward repeats, two reverse repeats, and five palindromic repeats. Additionally, a total of 118 perfect microsatellites were detected, with mononucleotide repeats being the most common (89.83%). By comparing the S. wilsonii chloroplast genome with those of other rosid plant species, significant contractions or expansions were identified at the IR-LSC/SSC borders. Phylogenetic analysis of 17 willow species confirmed that S. wilsonii was most closely related to S. chaenomeloides and revealed the monophyly of the genus Salix. The complete S. wilsonii chloroplast genome provides an additional sequence-based resource for studying the evolution of organelle genomes in woody plants.

scholarly journals Novel genetic code and record-setting AT-richness in the highly reduced plastid genome of the holoparasitic plant Balanophora

2018 ◽  
Vol 116 (3) ◽  
pp. 934-943 ◽  
Author(s):  
Huei-Jiun Su ◽  
Todd J. Barkman ◽  
Weilong Hao ◽  
Samuel S. Jones ◽  
Julia Naumann ◽  
...  
Keyword(s):  
Genetic Code ◽  
Selective Constraint ◽  
Trna Genes ◽  
The Novel ◽  
Overlapping Genes ◽  
Potential Consequence ◽  
Compositional Evolution ◽  
Plastid Genomes ◽  
Plastid Protein ◽  
The Many

Plastid genomes (plastomes) vary enormously in size and gene content among the many lineages of nonphotosynthetic plants, but key lineages remain unexplored. We therefore investigated plastome sequence and expression in the holoparasitic and morphologically bizarre Balanophoraceae. The two Balanophora plastomes examined are remarkable, exhibiting features rarely if ever seen before in plastomes or in any other genomes. At 15.5 kb in size and with only 19 genes, they are among the most reduced plastomes known. They have no tRNA genes for protein synthesis, a trait found in only three other plastid lineages, and thus Balanophora plastids must import all tRNAs needed for translation. Balanophora plastomes are exceptionally compact, with numerous overlapping genes, highly reduced spacers, loss of all cis-spliced introns, and shrunken protein genes. With A+T contents of 87.8% and 88.4%, the Balanophora genomes are the most AT-rich genomes known save for a single mitochondrial genome that is merely bloated with AT-rich spacer DNA. Most plastid protein genes in Balanophora consist of ≥90% AT, with several between 95% and 98% AT, resulting in the most biased codon usage in any genome described to date. A potential consequence of its radical compositional evolution is the novel genetic code used by Balanophora plastids, in which TAG has been reassigned from stop to tryptophan. Despite its many exceptional properties, the Balanophora plastome must be functional because all examined genes are transcribed, its only intron is correctly trans-spliced, and its protein genes, although highly divergent, are evolving under various degrees of selective constraint.

Molecular analysis of a 21.1-kb fragment of wheat chloroplast DNA bearing RNA polymerase subunit (rpo) genes

Genome ◽  
1999 ◽  
Vol 42 (6) ◽  
pp. 1042-1049
Author(s):  
Y Ohnishi ◽  
H Tajiri ◽  
Y Matsuoka ◽  
K Tsunewaki
Keyword(s):  
Rna Polymerase ◽  
Structural Features ◽  
Gene Arrangement ◽  
Grass Species ◽  
Trna Genes ◽  
Evolutionary Divergence ◽  
Protein Coding ◽  
Chloroplast Genomes ◽  
Intergenic Regions ◽  
Ct Dna

The entire nucleotide sequence of a 21.1-kb fragment of wheat chloroplast (ct) DNA was determined. This fragment carries 18 intact genes and parts of two additional genes, including the three RNA polymerase genes rpoB, rpoC1, and rpoC2. The gene arrangement of this region is conserved in wheat, rice, and maize, but not in non-grass species. Comparison of these 20 genes in wheat, rice, and maize showed that tRNA genes evolved more slowly than protein-coding genes in the chloroplast genome. Intergenic regions evolved much faster than both types of genes. Although the 19 genes of wheat, except for orf42, showed high identity to those of other plants, there were three novel structural features in the wheat rpoC2 gene; a deletion of 81 bp in the middle region, a variable insertion (408 bp), and a nonsense mutation in the 3' terminal region, resulting in truncation of a sequence of ca. 10 amino acids. An intermolecular recombination between the stretches of CTTAT and CTTTT was suggested as the mechanism of the 81-bp deletion in the wheat rpoC2 gene. Evolutionary distance between the chloroplast genomes of wheat and maize was larger than those between wheat and rice and between rice and maize.Key words: common wheat, chloroplast genes, evolutionary divergence, phylogeny.

Intraspecific mtDNA comparison of mycopathogen Mycogone perniciosa provides the insight into mitochondrial tRNA introns

2020 ◽  
Author(s):  
Jin You Deng ◽  
Xin Wu ◽  
Die Wen ◽  
Chen Hai Huang ◽  
Lei Yi Chen ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Rrna Genes ◽  
Universal Primers ◽  
Trna Genes ◽  
Mitochondrial Trna ◽  
High Sequence Similarity ◽  
Protein Coding ◽  
Protein Coding Genes ◽  
Intergenic Regions ◽  
Insertion Sites

Mycogone perniciosa is the main causative agent of wet bubble disease, which causes severe damage to the production of the cultivated mushroom Agaricus bisporus around the world. Whole-genome sequencing of twelve isolates of M. perniciosa was performed using the Illumina sequencing platform, and the obtained paired-end reads were used to assemble complete mitochondrial genomes. Intraspecific comparisons of conserved protein-coding genes, tRNA and rRNA genes, introns, and intergenic regions were conducted. Five different mtDNA haplotypes were detected among the tested isolates, ranging from 89,080 bp to 93,199 bp in length. All the mtDNAs contained the same set of 14 protein-coding genes (PCGs) and 2 rRNA and 27 tRNA genes, which shared high sequence similarity. In contrast, the number, insertion sites, and sequences of introns varied greatly among the mtDNAs. Eighteen out of 43 intergenic regions differed among the isolates, reflecting 65 SNPs, 76 indels, and the gain/loss of 9 long fragments. Intraspecific comparison revealed that two introns were located within tRNA genes, which is the first detailed description of mitochondrial tRNA introns. Intronic sequence comparison within the same insertion sites revealed the formation process of two introns, which also illustrated a fast evolutionary rate of introns among M. perniciosa isolates. Based on the intron distribution pattern, a pair of universal primers as well as four pairs of isolate-specific primers were designed, and were used to identify the five mtDNA types. In summary, the rapid gain or loss of mitochondrial introns could be an ideal marker for population genetics analysis.

An evaluation of mitochondrial tRNA gene evolution and its relation to the genetic code

1982 ◽  
Vol 60 (4) ◽  
pp. 475-479 ◽  
Author(s):  
R. J. Cedergren
Keyword(s):  
Genetic Code ◽  
Trna Gene ◽  
Gene Evolution ◽  
Sequence Data ◽  
Cellular Systems ◽  
Trna Genes ◽  
Gene Structures ◽  
And Function ◽  
First Time ◽  
Mitochondrial Trna Gene

Extensive sequence data on mitochondrial (mt) tRNAs give for the first time an opportunity to evaluate tRNA gene evolution in this organelle. Deductions from these gene structures relate to the evolution of tRNA genes in other cellular systems and to the origin of the genetic code. Mt tRNAs, in contrast to the prokaryotic nature of chloroplastic tRNA structure, can not at the present time be definitely related to either prokaryotic or eukaryotic tRNAs, probably because of a higher mutation rate in mitochondria.Fungal mt tRNAs having the same anticodon and function are generally similar enough to be considered homologous. Comparisons of all mt tRNA sequences contained in the same mitochondrion indicate that some tRNAs originated by duplication of a prototypic gene which, after divergence, led to tRNAs having different amino acid specificities. The deviant mt genetic code, although admittedly permitting a simpler decoding mechanism, is not useful in determining whether the origin of mitochondria had preceded or was derived from prokaryotes or eukaryotes, since the genetic code is variable even among mitochondria. Variants of the mt genetic code lead to speculation on the nature of die primordial code and its relation to the present "universal" code.

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