Respiration accumulates Calvin cycle intermediates for the rapid start of photosynthesis in Synechocystis sp. PCC 6803

Abstract

We tested the hypothesis that inducing photosynthesis in cyanobacteria requires respiration. A mutant deficient in glycogen phosphorylase (∆GlgP) was prepared in Synechocystis sp. PCC 6803 to suppress respiration. The accumulated glycogen in ΔGlgP was 250–450% of that accumulated in wild type (WT). The rate of dark respiration in ΔGlgP was 25% of that in WT. In the dark, P700⁺ reduction was suppressed in ΔGlgP, and the rate corresponded to that in (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone)-treated WT, supporting a lower respiration rate in ∆GlgP. Photosynthetic O₂-evolution rate reached a steady-state value much slower in ∆GlgP than in WT. This retardation was solved by addition of d-glucose. Furthermore, we found that the contents of Calvin cycle intermediates in ∆GlgP were lower than those in WT under dark conditions. These observations indicated that respiration provided the carbon source for regeneration of ribulose 1,5-bisphosphate in order to drive the rapid start of photosynthesis.

Graphical Abstract

Respiration provides the carbon source for regeneration of ribulose 1,5-bisphosphate in order to drive the rapid start of photosynthesis.

Key words:

• cyanobacteria
• respiration
• photosynthesis
• glycogen phosphorylase

Notes

Abbreviations: GlgP, glycogen phosphorylase; WT, wild type; Chl, chlorophyll; N, nitrogen.

Additional information

Funding

Funding. This work was supported by the Japan Society for the Promotion of Science (Scientific Research [grant number 21570041] to C.M.) and the Ministry of Education, Culture, Sports, Science, and Technology, Japan (Scientific Research on Innovative Area No. 22114512 to C.M.). The authors would like to thank Enago (www.enago.jp) for the English language review.