A role for glutathione reductase and glutathione in the tolerance of Chlamydomonas reinhardtii to photo‐oxidative stress

Abstract

The role of glutathione reductase (GR; EC 1.6.4.2) in the tolerance of Chlamydomonas reinhardtii P.A. Dangeard to high‐intensity light stress (HL, 1400 μmol m−2 s−1) was examined. Cells survived under high light (HL) stress, although their growth was inhibited after long‐term treatment (9‐24 h). GR activity increased 1 h after HL treatment. The contents of total glutathione, reduced glutathione (GSH) and glutathione disulfide (GSSG) increased 1‐3 h after HL treatment and then decreased after 24 h, while the GSH:GSSG ratio (glutathione redox potential) decreased after 3–9 h and recovered after 24 h. The transcript abundance of GR, CrGR1 (Cre06.g262100) and CrGR2 (Cre09.g396252) as well as glutathione synthesis‐related genes, CrGSH1 (Cre02g077100.t1.1) and CrGSH2 (Cre17.g70800.t1.1), increased with a peak near 1 h after HL treatment. Except for enhanced glutathione synthesis, the GR‐mediated glutathione redox machinery is also critical for the tolerance of C. reinhardtii cells to HL stress. Therefore, GR was downregulated or upregulated to investigate the importance of GR in HL tolerance. The CrGR1 knockdown amiRNA line exhibited low GR transcript abundance, GR activity and GSH:GSSG ratio and could not survive under HL conditions. Over‐expression of CrGR1 or CrGR2 driven by a HSP70A:RBCS2 fusion promoter resulted in a higher GR transcript abundance, GR activity and GSH:GSSG ratio and led to cell survival when exposed to high‐intensity illumination, i.e. 1800 μmol m−2 s−1. In conclusion, GR‐mediated modulation of the glutathione redox potential plays a role in the tolerance of Chlamydomonas cells to photo‐oxidative stress.

Photoinhibition and continuous growth of the wild-type and a high-light tolerant strain of Chlamydomonas reinhardtii

“…The green alga C. reinhardtii is usually cultured in laboratories at a PPFD of 100 µmol m -2 s -1 or less (Roach et al 2017, Xing et al 2017, Andrade et al 2018, Lin et al 2018, Yang et al 2018, and earlier growth tests suggest that wild-type C. reinhardtii does not grow rapidly in strong, oversaturating light (Schierenbeck et al 2015, Lin et al 2018. However, spontaneous mutations improving the ability to withstand high light occur frequently (Förster et al 2005).…”

Polyphenols of Salix aegyptiaca modulate the activities of drug metabolizing and antioxidant enzymes, and level of lipid peroxidation

“…SOD, one of the enzymes of defence system dismutates O 2 − to H 2 O 2 which is subsequently removed by catalase and GPx by reducing it to H 2 O [ 39 ]. GR is another important antioxidant enzyme that catalyses NADPH dependent reduction of glutathione disulphide (GSSG) to glutathione and maintains its level in the cell for the antioxidant functions [ 40 ]. Both the phytochemicals gallic acid and acetylsalicylic acid enhanced the specific activities of SOD, catalase, GPx and GR significantly, as consequence O 2 − likely to be dismuted and H 2 O 2 thus formed be reduced to H 2 O resulting into protection against oxidative stress.…”

Nickel and arsenite‐induced differential oxidative stress and antioxidant responses in two Anabaena species

“…Glutathione reductase (GR; EC 1.6.4.2) catalyzes the regeneration of GSH from glutathione disulfide (GSSG) using reducing equivalents from NAD(P)H . Thus, GR holds an important position by maintaining the intracellular glutathione pool mainly in the reduced state, i.e., GSH . Significant increase in the activity of GR (Fig.…”