Characterization of the influence of chlororespiration on the regulation of photosynthesis in the glaucophyte Cyanophora paradoxa

Abstract

Glaucophytes are primary symbiotic algae with unique plastids called cyanelles, whose structure is most similar to ancestral cyanobacteria among plastids in photosynthetic organisms. Here we compare the regulation of photosynthesis in glaucophyte with that in cyanobacteria in the aim of elucidating the changes caused by the symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways. Chlorophyll fluorescence measurements of the glaucophyte Cyanophora paradoxa NIES-547 indicated that plastoquinone (PQ) pool in photosynthetic electron transfer was reduced in the dark by chlororespiration. The levels of nonphotochemical quenching of chlorophyll fluorescence was high in the dark but decreased under low light, and increased again under high light. This type of concave light dependence was quite similar to that observed in cyanobacteria. Moreover, the addition of ionophore hardly affected nonphotochemical quenching, suggesting state transition as a main component of the regulatory system in C. paradoxa. These results suggest that cyanelles of C. paradoxa retain many of the characteristics observed in their ancestral cyanobacteria. From the viewpoint of metabolic interactions, C. paradoxa is the primary symbiotic algae most similar to cyanobacteria than other lineages of photosynthetic organisms.

Introducing an Arabidopsis thaliana Thylakoid Thiol/Disulfide-Modulating Protein Into Synechocystis Increases the Efficiency of Photosystem II Photochemistry

“…Both AtLQY1-expressing Synechocystis and the empty-vector control displayed reduced NPQ values as the growth light intensity increased from 25 to 50 µmol photons m -2 s -1 . This concave dependence of NPQ on actinic light intensities has been previously reported in Synechocystis and other cyanobacterial species (Campbell and Oquist, 1996; Misumi et al, 2016; Ogawa and Sonoike, 2016; Misumi and Sonoike, 2017). As the growth light intensity increased from 25 to 50 µmol photons m -2 s -1 , NPQ in the empty-vector control showed a 19% reduction whereas AtLQY1-expressing Synechocystis displayed a 45% reduction.…”

Respiration Interacts With Photosynthesis Through the Acceptor Side of Photosystem I, Reflected in the Dark-to-Light Induction Kinetics of Chlorophyll Fluorescence in the Cyanobacterium Synechocystis sp. PCC 6803

“…It is interesting to note that the peak height around 695 nm relative to that around 685 nm (F 695 /F 685 ) varied in different experimental conditions (Figure 1). Similar variation in the F 695 /F 685 ratio has been also observed in Synechococcus elongatus PCC 6301 (Mullineaux and Allen, 1990) or even in glaucophyte (Misumi and Sonoike, 2017), suggesting that the change is widely observed in phycobilisome-containing organisms. The origin of the fluorescence peak around 685 nm or that around 695 nm was first assigned to the PSII core subunits, CP43 (PsbC) or CP47 (PsbD), respectively (Yamagishi and Katoh, 1983).…”

Oxidation of P700 Ensures Robust Photosynthesis

“…Generally, Glaucophyta is characterized by the same definition (Archaeplastida) as Chlorophyta (green algae) and Rhodophyta (red algae), but in this study we do not review P700 oxidation system in Glaucophyta because of scant existing literature on the subject. But recently, the glaucophyte Cyanophora paradoxa has been reported to develop cyanobacteria-like regulatory mechanisms of the photosynthetic electron transport system ( Misumi and Sonoike, 2017 ).…”