Transcriptional and physiological responses to inorganic nutrition in a tropical Pacific strain of Alexandrium minutum

Implications for nutrient uptakes and assimilation

Kieng Soon Hii, Po Teen Lim, Nyuk Fong Kon, Gires Usup, Haifeng Gu, Chui Pin Leaw

Research output: Contribution to journalArticle

Abstract

The marine dinoflagellate Alexandrium minutum is known to produce saxitoxins that cause paralytic shellfish poisoning in human worldwide through consumption of the contaminated shellfish mollusks. Despite numerous studies on the growth physiology and saxitoxin production of this species, the knowledge on the molecular basis of nutrient uptakes in relation to toxin production in this species is limited. In this study, relative expressions of the high-affinity transporter genes of nitrate, ammonium, and phosphate (AmNrt2, AmAmt1 and AmPiPT1) and the assimilation genes, nitrate reductase (AmNas), glutamine synthase (AmGSIII) and carbamoyl phosphate synthase (AmCPSII) from A. minutum were studied in batch clonal culture condition with two nitrogen sources (nitrate: NO3 or ammonium: NH4 +) under different N:P ratios (high-P: N:P of 14 and 16, and low-P: N:P of 155). The expression of AmAmt1 was suppressed in excess NH4 +-grown condition but was not observed in AmNrt2 and AmNas. Expressions of AmAmt1, AmNrt2, AmNas, AmGSIII, AmCPSII, and AmPiPT1 were high in P-deficient condition, showing that A. minutum is likely to take up nutrients for growth under P-stress condition. Conversely, relative expression of AmCPSII was incongruent with cell growth, but was well correlated with toxin quota, suggesting that the gene might involve in arginine metabolism and related toxin production pathway. The expression of AmGSIII is found coincided with higher toxin production and is believed to involve in mechanism to detoxify the cells from excess ammonium stress. The gene regulation observed in this study has provided better insights into the ecophysiology of A. minutum in relation to its adaptive strategies in unfavorable environments.

Original languageEnglish
Article number143950
JournalGene
Volume711
DOIs
Publication statusPublished - 30 Aug 2019

Fingerprint

Saxitoxin
Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)
Ammonium Compounds
Genes
Growth
Shellfish Poisoning
Dinoflagellida
Nitrate Reductase
Shellfish
Batch Cell Culture Techniques
Mollusca
Nitrates
Arginine
Nitrogen
Food

Keywords

  • Ammonium detoxification
  • Nutrient assimilation genes
  • Nutrient transporter genes
  • Paralytic shellfish toxin
  • Saxitoxins

ASJC Scopus subject areas

  • Genetics

Cite this

Transcriptional and physiological responses to inorganic nutrition in a tropical Pacific strain of Alexandrium minutum : Implications for nutrient uptakes and assimilation. / Hii, Kieng Soon; Lim, Po Teen; Kon, Nyuk Fong; Usup, Gires; Gu, Haifeng; Leaw, Chui Pin.

In: Gene, Vol. 711, 143950, 30.08.2019.

Research output: Contribution to journalArticle

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