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The chloroplast and mitochondrial genomes of the green algae Pediastrum duplex isolated from Central Georgia (USA).

ABSTRACT: A Pediastrum duplex (Chlorophyta) strain was isolated from a freshwater system in Milledgeville, Georgia and its chloroplast and mitochondrial genomes sequenced. The chloroplast genome was 199,241?bp with 136 genes and the mitochondrial 40,756?bp with 40 genes, both were circular. Comparison of the 'Milledgeville' plastome to other P. duplex isolates revealed a nearly identical sequence identity to archived genes and genomic fragments from the strain UTEX1364 which was isolated from Lake Machovo in 1962. These sequences provide chloroplast and mitochondrial genomes from a wild P. duplex isolate and provide more organelle genomes for a genus with cryptic phylogenetic relationships.

SUBMITTER: Proulex GCR

PROVIDER: S-EPMC7706855 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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The chloroplast and mitochondrial genomes of the green algae Pediastrum duplex isolated from Central Georgia (USA).

Proulex Grayson C R GCR Lor Blia B Manoylov Kalina M KM Cahoon A Bruce AB

Mitochondrial DNA. Part B, Resources 20190919 2

A Pediastrum duplex (Chlorophyta) strain was isolated from a freshwater system in Milledgeville, Georgia and its chloroplast and mitochondrial genomes sequenced. The chloroplast genome was 199,241 bp with 136 genes and the mitochondrial 40,756 bp with 40 genes, both were circular. Comparison of the 'Milledgeville' plastome to other P. duplex isolates revealed a nearly identical sequence identity to archived genes and genomic fragments from the strain UTEX1364 which was isolated fro ...[more]

PMID: 33365860

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Project description:BACKGROUND:Comparative studies of chloroplast genomes (plastomes) across the Chlorophyceae are revealing dynamic patterns of size variation, gene content, and genome rearrangements. Phylogenomic analyses are improving resolution of relationships, and uncovering novel lineages as new plastomes continue to be characterized. To gain further insight into the evolution of the chlorophyte plastome and increase the number of representative plastomes for the Sphaeropleales, this study presents two fully sequenced plastomes from the green algal family Hydrodictyaceae (Sphaeropleales, Chlorophyceae), one from Hydrodictyon reticulatum and the other from Pediastrum duplex. METHODS:Genomic DNA from Hydrodictyon reticulatum and Pediastrum duplex was subjected to Illumina paired-end sequencing and the complete plastomes were assembled for each. Plastome size and gene content were characterized and compared with other plastomes from the Sphaeropleales. Homology searches using BLASTX were used to characterize introns and open reading frames (orfs) ≥ 300 bp. A phylogenetic analysis of gene order across the Sphaeropleales was performed. RESULTS:The plastome of Hydrodictyon reticulatum is 225,641 bp and Pediastrum duplex is 232,554 bp. The plastome structure and gene order of H. reticulatum and P. duplex are more similar to each other than to other members of the Sphaeropleales. Numerous unique open reading frames are found in both plastomes and the plastome of P. duplex contains putative viral protein genes, not found in other Sphaeropleales plastomes. Gene order analyses support the monophyly of the Hydrodictyaceae and their sister relationship to the Neochloridaceae. DISCUSSION:The complete plastomes of Hydrodictyon reticulatum and Pediastrum duplex, representing the largest of the Sphaeropleales sequenced thus far, once again highlight the variability in size, architecture, gene order and content across the Chlorophyceae. Novel intron insertion sites and unique orfs indicate recent, independent invasions into each plastome, a hypothesis testable with an expanded plastome investigation within the Hydrodictyaceae.

Project description:Interspecific differences in the response of microalgae to stress have numerous ecological implications. However, little is known of intraspecific sensitivities and the potential role of local genetic adaptation of populations. We compared the allelochemical sensitivity of 23 Pediastrum duplex Meyen strains, a common component of the freshwater phytoplankton. In order to test for local genetic adaptation, strains were isolated from water bodies with and without the allelopathically-active submerged macrophyte Myriophyllum. Strains were assigned to P. duplex on the basis of cell shape and colony morphology and only P. duplex strains that belonged to the same lineage in an ITS rDNA phylogeny were used. Inhibition of strain growth rates and maximum quantum yields of photosystem II were measured after exposure to tannic acid (TA) and co-culture with Myriophyllum spicatum. Growth rate inhibition varied over one order of magnitude between the P. duplex strains. There was no correlation between the presence of Myriophyllum in the source location and the sensitivity of the strains to TA or the presence of Myriophyllum, suggesting that at least strong unidirectional local adaptation to Myriophyllum had not taken place in the studied water bodies. The maximum quantum yield of photosystem II of TA exposed algae decreased, whereas the yield of algae exposed to M. spicatum was slightly higher than that of the controls. The ranking of P. duplex strain sensitivities differed between the types of exposure (single additions of TA versus co-existence with M. spicatum) and the parameter measured (growth rate versus maximum quantum yield), emphasizing the importance of measuring multiple traits when analysing strain-specific sensitivities towards allelochemicals. The observation that sensitivities to allelochemicals vary widely among strains of a single freshwater algal species should be taken into account if evaluating ecological consequences of allelopathic interactions.

Project description:BackgroundTerrestrial, freshwater and marine green algae constitute the large and morphologically diverse phylum of Chlorophyta, which gave rise to the core chlorophytes. Chlorophyta are abundant and diverse in freshwater environments where sometimes they form nuisance blooms under eutrophication conditions. The phylogenetic relationships among core chlorophyte clades (Chlorodendrophyceae, Ulvophyceae, Trebouxiophyceae and Chlorophyceae), are of particular interest as it is a species-rich phylum with ecological importance worldwide, but are still poorly understood. In the Mediterranean ecoregion, data on molecular characterization of eukaryotic microalgae strains are limited and current knowledge is based on ecological studies of natural populations. In the present study we report the isolation and characterization of 11 green microalgae strains from Greece contributing more information for the taxonomy of Chlorophyta. The study combined morphological and molecular data.ResultsPhylogenetic analysis based on 18S rRNA, internal transcribed spacer (ITS) region and the large subunit of the ribulose-bisphosphate carboxylase (rbcL) gene revealed eight taxa. Eleven green algae strains were classified in four orders (Sphaeropleales, Chlorellales, Chlamydomonadales and Chaetophorales) and were represented by four genera; one strain was not assigned to any genus. Most strains (six) were classified to the genus Desmodesmus, two strains to genus Chlorella, one to genus Spongiosarcinopsis and one filamentous strain to genus Uronema. One strain is placed in a separate independent branch within the Chlamydomonadales and deserves further research.ConclusionsOur study reports, for the first time, the presence of Uronema in an aquatic environment up to 40 °C and reveals new diversity within the Chlamydomonadales. The results from the ITS region and the rbcL gene corroborated those obtained from 18S rRNA without providing further information or resolving the phylogenetic relationships within certain genera, due to the limited number of ITS and rbcL sequences available. The comparison of molecular and morphological data showed that they were congruent. Cosmopolitan genera with high worldwide distribution inhabit Greek freshwaters.

Dataset Information

The chloroplast and mitochondrial genomes of the green algae Pediastrum duplex isolated from Central Georgia (USA).

Publications

The chloroplast and mitochondrial genomes of the green algae <i>Pediastrum duplex</i> isolated from Central Georgia (USA).

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