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Six domoic acid related compounds from the red alga, Chondria armata, and domoic acid biosynthesis by the diatom, Pseudo-nitzschia multiseries.

ABSTRACT: Domoic acid (DA, 1), a potent neurotoxin that causes amnesic shellfish poisoning, has been found in diatoms and red algae. While biosynthetic pathway towards DA from geranyl diphosphate and L-glutamate has been previously proposed, its late stage is still unclear. Here, six novel DA related compounds, 7'-methyl-isodomoic acid A (2) and B (3), N-geranyl-L-glutamic acid (4), 7'-hydroxymethyl-isodomoic acid A (5) and B (6), and N-geranyl-3(R)-hydroxy-L-glutamic acid (7), were isolated from the red alga, Chondria armata, and their structures were determined. The compounds 4 and 7, linear compounds, are predictable as the precursors to form the DA pyrrolidine ring. The compounds 2 and 3 are thought as the cyclized products of 7; therefore, dehydration and electron transfer from the internal olefin of 7 is a possible mechanism for the pyrrolidine ring formation. One terminal methyl group of the side chain of 2 and 3 is predicted to be oxidized to hydroxymethyl (5, 6), and then to carboxylic acids, forming isodomoic acids A and B. Finally, the terminal olefin of isodomoic acid A would be isomerized to form DA. In addition, [15N, D]-labeled 4 was incorporated into DA using the diatom, Pseudo-nitzschia multiseries, demonstrating that 4 is the genuine precursor of DA.

SUBMITTER: Maeno Y

PROVIDER: S-EPMC5762911 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Six domoic acid related compounds from the red alga, Chondria armata, and domoic acid biosynthesis by the diatom, Pseudo-nitzschia multiseries.

Maeno Yukari Y Kotaki Yuichi Y Terada Ryuta R Cho Yuko Y Konoki Keiichi K Yotsu-Yamashita Mari M

Scientific reports 20180110 1

Domoic acid (DA, 1), a potent neurotoxin that causes amnesic shellfish poisoning, has been found in diatoms and red algae. While biosynthetic pathway towards DA from geranyl diphosphate and L-glutamate has been previously proposed, its late stage is still unclear. Here, six novel DA related compounds, 7'-methyl-isodomoic acid A (2) and B (3), N-geranyl-L-glutamic acid (4), 7'-hydroxymethyl-isodomoic acid A (5) and B (6), and N-geranyl-3(R)-hydroxy-L-glutamic acid (7), were isolated from the red ...[more]

PMID: 29321590

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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.

Dataset Information

Six domoic acid related compounds from the red alga, Chondria armata, and domoic acid biosynthesis by the diatom, Pseudo-nitzschia multiseries.

Publications

Six domoic acid related compounds from the red alga, Chondria armata, and domoic acid biosynthesis by the diatom, Pseudo-nitzschia multiseries.

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