2-Cys Peroxiredoxins Participate in the Oxidation of Chloroplast Enzymes in the Dark

Abstract

Most redox-regulated chloroplast enzymes are reduced during the day and oxidized during the night. While the reduction mechanism of light-dependent enzymes is well known, the mechanism mediating their oxidation in the dark remains unknown. The thiol-dependent peroxidases, 2-Cys peroxiredoxins (Prxs), play a key role in light-dependent reduction of chloroplast enzymes. Prxs transfer reducing equivalents of thiols to hydrogen peroxide, suggesting the participation of these peroxidases in enzyme oxidation in the dark. Here, we have addressed this issue by analyzing the redox state of well-known redox-regulated chloroplast enzymes in response to darkness in Arabidopsis thaliana mutants deficient in chloroplastlocalized Prxs (2-Cys Prxs A and B, Prx IIE, and Prx Q). Mutant plants lacking 2-Cys Prxs A and B, and plants overexpressing NADPH-dependent thioredoxin (Trx) reductase C showed delayed oxidation of chloroplast enzymes in the dark. In contrast, the deficiencies of Prx IIE or Prx Q exerted no effect. In vitro assays allowed the reconstitution of the pathway of reducing equivalents from reduced fructose 1,6bisphosphatase to hydrogen peroxide mediated by Trxs and 2-Cys Prxs. Taken together, these results suggest that 2-Cys Prxs participate in the short-term oxidation of chloroplast enzymes in the dark.

Redox regulation of PGRL1 at the onset of low light intensity

“…There is a growing body of evidence for special disulfidebased regulation of fast chloroplast responses at low light levels (Rintamaki et al, 2000;Trebitsh and Danon, 2001;Martinsuo et al, 2003;Piippo et al, 2006;Tikkanen et al, 2010;Dangoor et al, 2012;Eliyahu et al, 2015;Nikkanen et al, 2016;Ojeda et al, 2018;Yoshida et al, 2018a;Cejudo et al, 2019;Cerveau et al, 2019). This study, conducted in vivo at the onset of low light intensity, revealed extensive reversible changes in the PGRL1 disulfide state, mainly the reduction and reoxidation of 59 kDa DSBC, that were necessary for its previously identified adaptive function in the rapid activation of CEF that transiently overacidifies the lumen and activates NPQ until CO 2 assimilation is fully activated (Munekage et al, 2002;Finazzi et al, 2004;Li et al, 2004;Joliot and Joliot, 2006;Cardol et al, 2010).…”

“…Therefore, as an example, the activation by reduction of regulatory disulfide-containing proteins at the onset of light depends on their typical oxidation at night. There is a growing body of direct and indirect evidence for partial oxidation of chloroplast disulfide-regulated proteins at low to moderate light levels as well (Rintamaki et al, 2000;Trebitsh and Danon, 2001;Martinsuo et al, 2003;Piippo et al, 2006;Tikkanen et al, 2010;Dangoor et al, 2012;Eliyahu et al, 2015;Nikkanen et al, 2016;Ojeda et al, 2018;Yoshida et al, 2018a;Cejudo et al, 2019;Cerveau et al, 2019). Conceivably, partial oxidation could poise further activation of the protein by the stimulated level of reductive signals in sudden increases in light intensity.…”

“…Several independent experiments have revealed a role for 2-Cys peroxiredoxin (2-Cys Prx) in the formation of regulatory disulfides in chloroplast enzymes in both dark and light conditions (Dangoor et al, 2012;Eliyahu et al, 2015;Ojeda et al, 2018;Vaseghi et al, 2018;Yoshida et al, 2018b). It was further found that the coupled reactions of 2-Cys Prx and the atypical thioredoxins ACHT1 or ACHT4 combined to form regulatory oxidative pathways in low to moderate light levels (Dangoor et al, 2012;Eliyahu et al, 2015).…”

Increased expression of mitochondrial dysfunction stimulon genes affects chloroplast redox status and photosynthetic electron transfer in Arabidopsis

“…The above-described and previously published results indicated decreased ROS production in the chloroplasts of rcd1 and other MDS-inducing mutants or treatments [9, 20, 21]. Chloroplastic ROS act as an electron sink for thiol redox enzymes [10–12]. Thus, suppressed ROS production likely results in more reduced redox state of these enzymes.…”

“…Similarly to 2-CP, the NTRC pool was more reduced in rcd1 than in wild type both in light and darkness (Fig 6A). This enzyme controls a number of chloroplastic processes including ROS processing [10, 11, 44], activities of thylakoid NADH dehydrogenase (NDH) complex mediating cyclic electron transfer [45], and of ATP synthase [46, 47].…”