<div><p>We tested the hypothesis that inducing photosynthesis in cyanobacteria requires respiration. A mutant deficient in glycogen phosphorylase (∆GlgP) was prepared in <i>Synechocystis</i> 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<sup>+</sup> reduction was suppressed in ΔGlgP, and the rate corresponded to that in (2,5-dibromo-3-methyl-6-isopropyl-<i>p</i>-benzoquinone)-treated WT, supporting a lower respiration rate in ∆GlgP. Photosynthetic O<sub>2</sub>-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.</p></div
