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. 2023 Sep 18;21(9):497.
doi: 10.3390/md21090497.

Nutrient Deficiencies Impact on the Cellular and Metabolic Responses of Saxitoxin Producing Alexandrium minutum: A Transcriptomic Perspective

Muhamad Afiq Akbar  1   2   3 , Nurul Yuziana Mohd Yusof  4 , Gires Usup  4 , Asmat Ahmad  5 , Syarul Nataqain Baharum  3 , Hamidun Bunawan  3
Affiliations

Nutrient Deficiencies Impact on the Cellular and Metabolic Responses of Saxitoxin Producing Alexandrium minutum: A Transcriptomic Perspective

Muhamad Afiq Akbar et al. Mar Drugs. .

Abstract

Dinoflagellate Alexandrium minutum Halim is commonly associated with harmful algal blooms (HABs) in tropical marine waters due to its saxitoxin production. However, limited information is available regarding the cellular and metabolic changes of A. minutum in nutrient-deficient environments. To fill this gap, our study aimed to investigate the transcriptomic responses of A. minutum under nitrogen and phosphorus deficiency. The induction of nitrogen and phosphorus deficiency resulted in the identification of 1049 and 763 differently expressed genes (DEGs), respectively. Further analysis using gene set enrichment analysis (GSEA) revealed 702 and 1251 enriched gene ontology (GO) terms associated with nitrogen and phosphorus deficiency, respectively. Our results indicate that in laboratory cultures, nitrogen deficiency primarily affects meiosis, carbohydrate catabolism, ammonium assimilation, ion homeostasis, and protein kinase activity. On the other hand, phosphorus deficiency primarily affects the carbon metabolic response, cellular ion transfer, actin-dependent cell movement, signalling pathways, and protein recycling. Our study provides valuable insights into biological processes and genes regulating A. minutum's response to nutrient deficiencies, furthering our understanding of the ecophysiological response of HABs to environmental change.

Keywords: gene set enrichment analysis; harmful algae blooms; saxitoxin; transcriptomics.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Comparison of unigene expression values between all samples. (A) Scatter plot comparing unigene expression values for biological replicates and (B) 3D PCA plot of unigene expression values for all samples.
Figure 2
Figure 2
A. minutum unigenes expressed differently under the induction of nitrogen and phosphorus deficiency. (A) The heat map based on TPM log values (B) MA plot displays all DEGs. Red dots represent up-regulated DEGs, while blue dots represent down-regulated DEGs.
Figure 3
Figure 3
Top three enriched GO terms by A. minutum under the following conditions. (A) Nitrogen deficiency (B) Phosphorus deficiency.
Figure 4
Figure 4
Enrichment map visualization for enriched GO terms by A. minutum under the induction of nitrogen deficiency. Each node corresponds to enriched GO terms in response to nitrogen deficiency, and the nodes’ size is related to the NES value for the enriched GO term. Edges (green lines) connect GO terms to shared genes, and line thickness is associated with the number of genes shared between the GO terms.
Figure 5
Figure 5
The Enrichment map visualizes the enriched gene ontology (GO) terms in response to phosphorus deficiency in A. minutum. Each node in the map represents an enriched GO term, with node size reflecting the normalized enrichment score (NES) for the term. The green edges indicate shared genes between the GO terms, with the thickness of the line indicating the number of shared genes.
Figure 6
Figure 6
The experimental design adopted to induce nitrogen and phosphorus deficiency in A. minutum.
Figure 7
Figure 7
Workflow for transcriptomics data analysis used in this study.
See this image and copyright information in PMC

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