High impact information on PETC

• To assess whether ferredoxin (Fd) donates electrons directly to plastoquinone (PQ) or via a Q-cycle in the cytochrome (cyt) b(6)f complex in PSI cyclic electron transport, we characterized the activity of PSI cyclic electron transport in an Arabidopsis mutant, pgr1 (proton gradient regulation) [1].
• In pgr1, Q-cycle activity was hypersensitive to acidification of the thylakoid lumen because of an amino acid alteration in the Rieske subunit of the cyt b(6)f complex, resulting in a conditional defect in Q-cycle activity [1].
• All the results indicated that the pgr1 mutation did not affect PGR5-dependent PQ reduction by Fd [1].
• In contrast to the pgr5 defect, the pgr1 defect did not show any synergistic effect on the quantum yield of photosystem II in crr2-2, a mutant in which NDH (NAD(P)H dehydrogenase) activity was impaired [1].
• Map-based cloning showed that pgr1 had a point mutation in petC encoding the Rieske subunit of the cytochrome b(6)f complex [2].

Biological context of PETC

• The photosynthetic electron transport chain (PETC) is the principal place of appearance of reactive oxygen species (ROS) in plants under illumination [3].
• We showed that pgr1 was sensitive to changes in light conditions, demonstrating that maximum activity of the cytochrome b(6)f complex is indispensable for short-term acclimation [2].
• The amino acid sequence of CAO predicts mononuclear iron and Rieske iron-sulfur centers in the protein [4].

Anatomical context of PETC

• The data imply that the pH-dependent inactivation of electron transport through cyt b6/f is shifted by about 1 pH unit to more alkaline pH values in pgr1 thylakoids in comparison with wild-type thylakoids [5].

Associations of PETC with chemical compounds

• Single point mutation in the Rieske iron-sulfur subunit of cytochrome b6/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis [5].
• For the transcripts of sAPx and Csd2 high correlations with the calculated redox state of NADPH were observed in pgr1, but not in wild-type, suggesting that in wild-type plants signals depending on thylakoid acidification overlay a predominant redox-signal [6].

Other interactions of PETC

• We isolated an Arabidopsis mutant, pgr1 (proton gradient regulation), entirely lacking thermal dissipation, which was observed as little non-photochemical quenching of chlorophyll fluorescence [2].

References