Dataset Information

Sexual reproduction and genetic polymorphism within the cosmopolitan marine diatom Pseudo-nitzschia pungens.

ABSTRACT: Different clades belonging to the cosmopolitan marine diatom Pseudo-nitzschia pungens appear to be present in different oceanic environments, however, a 'hybrid zone', where populations of different clades interbreed, has also been reported. Many studies have investigated the sexual reproduction of P. pungens, focused on morphology and life cycle, rather than the role of sexual reproduction in mixing the genomes of their parents. We carried out crossing experiments to determine the sexual compatibility/incompatibility between different clades of P. pungens, and examined the genetic polymorphism in the ITS2 region. Sexual reproduction did not occur only between clades II and III under any of experimental temperature conditions. Four offspring strains were established between clade I and III successfully. Strains established from offspring were found interbreed with other offspring strains as well as viable with their parental strains. We confirmed the hybrid sequence patterns between clades I and III and found novel sequence types including polymorphic single nucleotide polymorphisms (SNPs) in the offspring strains. Our results implicate that gene exchange and mixing between different clades are still possible, and that sexual reproduction is a significant ecological strategy to maintain the genetic diversity within this diatom species.

SUBMITTER: Kim JH

PROVIDER: S-EPMC7326933 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Sexual reproduction and genetic polymorphism within the cosmopolitan marine diatom Pseudo-nitzschia pungens.

Kim Jin Ho JH Ajani Penelope P Murray Shauna A SA Kim Joo-Hwan JH Lim Hong Chang HC Teng Sing Tung ST Lim Po Teen PT Han Myung-Soo MS Park Bum Soo BS

Scientific reports 20200630 1

Different clades belonging to the cosmopolitan marine diatom Pseudo-nitzschia pungens appear to be present in different oceanic environments, however, a 'hybrid zone', where populations of different clades interbreed, has also been reported. Many studies have investigated the sexual reproduction of P. pungens, focused on morphology and life cycle, rather than the role of sexual reproduction in mixing the genomes of their parents. We carried out crossing experiments to determine the sexual compat ...[more]

PMID: 32606343

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Project description:BackgroundPseudo-nitzschia multiseries Hasle (Hasle) (Ps-n) is distinctive among the ecologically important marine diatoms because it produces the neurotoxin domoic acid. Although the biology of Ps-n has been investigated intensely, the characterization of the genes and biochemical pathways leading to domoic acid biosynthesis has been limited. To identify transcripts whose levels correlate with domoic acid production, we analyzed Ps-n under conditions of high and low domoic acid production by cDNA microarray technology and reverse-transcription quantitative PCR (RT-qPCR) methods. Our goals included identifying and validating robust reference genes for Ps-n RNA expression analysis under these conditions.ResultsThrough microarray analysis of exponential- and stationary-phase cultures with low and high domoic acid production, respectively, we identified candidate reference genes whose transcripts did not vary across conditions. We tested eleven potential reference genes for stability using RT-qPCR and GeNorm analyses. Our results indicated that transcripts encoding JmjC, dynein, and histone H3 proteins were the most suitable for normalization of expression data under conditions of silicon-limitation, in late-exponential through stationary phase. The microarray studies identified a number of genes that were up- and down-regulated under toxin-producing conditions. RT-qPCR analysis, using the validated controls, confirmed the up-regulation of transcripts predicted to encode a cycloisomerase, an SLC6 transporter, phosphoenolpyruvate carboxykinase, glutamate dehydrogenase, a small heat shock protein, and an aldo-keto reductase, as well as the down-regulation of a transcript encoding a fucoxanthin-chlorophyll a-c binding protein, under these conditions.ConclusionOur results provide a strong basis for further studies of RNA expression levels in Ps-n, which will contribute to our understanding of genes involved in the production and release of domoic acid, an important neurotoxin that affects human health as well as ecosystem function.

Project description:Pseudo-nitzschia multistriata is a planktonic diatom species with a diplontic life cycle comprising a short sexual phase during which gametes are produced from the encounter of two diploid cells of opposite mating type (MT). Gene expression studies have highlighted the presence of substantial changes occurring at the onset of sexual reproduction. Collectively, there is clear evidence of a chemical cross talk which mediates the mating step.Herein, we have hypothesized that these major transcriptomic changes are associated to variations in the amount and nature of the metabolites produced by the cells. In order to investigate such chemical diversity in an unbiased manner, we undertook an untargeted metabolomics approach. Liquid chromatography – tandem mass spectrometry was applied to investigate the differences in the metabolic profiles between control cells in the vegetative phase (MT+ and MT-) and mixed strains of opposite MTs (cross) undergoing sexual reproduction. Of the 2408 high-quality features obtained, 70 known metabolites could be identified based on in-house libraries and online databases; molecular networking proved valuable to classify additional 47 non-identified features.The present exploratory study provides an overview of the chemical diversity detectable in P. multistriata, presenting a dynamic picture of the changes occurring during sexual reproduction. In particular, the reduction of phytol detected in the cross can be linked to the general downregulation of photosynthesis during sexual reproduction observed elsewhere. The dysregulation of other metabolites stands as a starting point for the understanding of the mechanisms regulating sexual reproduction: a metabolite that was tentatively identified as 7-dehydrodesmosterol exhibited the highest upregulation in the comparison between the two MTs of opposite sex, as well as between MT+ vs cross.The effects of extraction solvents and harvesting times on the ensemble of endo-metabolites were also analyzed.

Dataset Information

Sexual reproduction and genetic polymorphism within the cosmopolitan marine diatom Pseudo-nitzschia pungens.

Publications

Sexual reproduction and genetic polymorphism within the cosmopolitan marine diatom Pseudo-nitzschia pungens.

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