Abstract
Alexandrium minutum and Alexandrium tamutum are two closely related harmful algal bloom (HAB)-causing species with different toxicity. Using isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics and two-dimensional differential gel electrophoresis (2D-DIGE), a comprehensive characterization of the proteomes of A. minutum and A. tamutum was performed to identify the cellular and molecular underpinnings for the dissimilarity between these two species. A total of 1436 proteins and 420 protein spots were identified using iTRAQ-based proteomics and 2D-DIGE, respectively. Both methods revealed little difference (10–12%) between the proteomes of A. minutum and A. tamutum, highlighting that these organisms follow similar cellular and biological processes at the exponential stage. Toxin biosynthetic enzymes were present in both organisms. However, the gonyautoxin-producing A. minutum showed higher levels of osmotic growth proteins, Zn-dependent alcohol dehydrogenase and type-I polyketide synthase compared to the non-toxic A. tamutum. Further, A. tamutum had increased S-adenosylmethionine transferase that may potentially have a negative feedback mechanism to toxin biosynthesis. The complementary proteomics approach provided insights into the biochemistry of these two closely related HAB-causing organisms. The identified proteins are potential biomarkers for organismal toxicity and could be explored for environmental monitoring.
Highlights
Accepted: 17 December 2020The genus Alexandrium is one of the major harmful algal bloom (HAB)-causing genera in terms of global diversity, magnitude and consequences of blooms [1,2,3]
Toxins 2021, Key Contribution: We report the proteomes of the HAB-causing Alexandrium minutum and Alexandrium tamutum and showed key differences and similarities
An immunostaining differentiation between A. minutum and A. tamutum using an antibody raised against A. minutum cell lysates was conducted to assess the biochemical difference between these organisms
Summary
The genus Alexandrium is one of the major harmful algal bloom (HAB)-causing genera in terms of global diversity, magnitude and consequences of blooms [1,2,3]. The proliferation of this dinoflagellate in the marine environment causes deleterious effects to the economy and human health. Alexandrium minutum Halim 1960 and Alexandrium tamutum Montresor 2004 are closely related species. Both A. minutum and A. tamutum are oval to elliptical in shape, with the latter slightly pentagonal in some cases. A. minutum is hemispherical in shape whereas A. tamutum is elliptical (Figure 1)
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