Ascorbate-glutathione cycle alleviates low-temperature-induced oxidative stress for augmented growth of Nannochloropsis oceanica Rose Bengal mutants

Tsung Yu Tsai, Inna Khozin-Goldberg, Avigad Vonshak, Tse Min Lee

Research output: Contribution to journalArticlepeer-review

Abstract

Studying the adaptive mechanisms of algae to abiotic stresses, such as low temperature and high light intensities, can help facilitate large-scale outdoor production. Consequently, the role played by the antioxidant defense system in the tolerance of Nannochloropsis oceanica Rose Bengal (RB) mutants, with a truncated PSII complex, to low-temperature (LT, 18°C) under high-light (HL, 250 μmol⋅m−2⋅s−1) conditions was explored. The wild type (WT) exhibited O2•- and H2O2 accumulation, lipid peroxidation, and cell death upon LT treatment, which was exacerbated by LT-HL. The RB mutants showed no oxidative stress during LT or LT-HL. Ascorbate peroxidase (APX; EC 1.11.1.11), dehydroascorbate reductase (DHAR; EC 1.8.5.1), and glutathione reductase (GR; E.C. 1.6.4.2) activity and transcript abundance increased by LT and LT-HL conditions in the RB mutants but not in the WT. In the RB mutants, the ascorbate (AsA) pool size stayed low, but the AsA/DHA ratio increased under LT and LT-HT conditions, while the glutathione (GSH) pool size and GSH/GSSG ratio increased. The RB mutants treated with buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis, became susceptible to LT-HL stress. The expression of GLUTAMYLCYSTEINE SYNTHETASE (NoGSH1) and GLUTATHIONE SYNTHASE (NoGSH2A and NoGSH2B), responsible for GSH biosynthesis, was upregulated in two RB mutants by LT and LT-HL stress, while that of GULONOLACTONE OXIDASE (NoGulo), involved in AsA biosynthesis, remained constant. Beyond reduced light energy absorption, increased the Ascorbate-Glutathione cycle enzyme expression and AsA and GSH regeneration in Nannochloropsis RB mutants enable adaptations to prevent oxidative damage caused by high-intensity illumination at low temperatures.

Original languageEnglish
Article numbere14168
JournalPhysiologia Plantarum
Volume176
Issue number1
DOIs
StatePublished - 1 Jan 2024

ASJC Scopus subject areas

  • Physiology
  • Genetics
  • Plant Science
  • Cell Biology

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