Systematic Analysis of the Relation of Electron Transport and ATP Synthesis to the Photodamage and Repair of Photosystem II in Synechocystis

Abstract

(I.S., N.M.) The photosynthetic machinery and, in particular, the photosystem II (PSII) complex are susceptible to strong light, and the effects of strong light are referred to as photodamage or photoinhibition. In living organisms, photodamaged PSII is rapidly repaired and, as a result, the extent of photoinhibition represents a balance between rates of photodamage and the repair of PSII. In this study, we examined the roles of electron transport and ATP synthesis in these two processes by monitoring them separately and systematically in the cyanobacterium Synechocystis sp. PCC 6803. We found that the rate of photodamage, which was proportional to light intensity, was unaffected by inhibition of the electron transport in PSII, by acceleration of electron transport in PSI, and by inhibition of ATP synthesis. By contrast, the rate of repair was reduced upon inhibition of the synthesis of ATP either via PSI or PSII. Northern blotting and radiolabeling analysis with [ 35 S]Met revealed that synthesis of the D1 protein was enhanced by the synthesis of ATP. Our observations suggest that ATP synthesis might regulate the repair of PSII, in particular, at the level of translation of the psbA genes for the precursor to the D1 protein, whereas neither electron transport nor the synthesis of ATP affects the extent of photodamage.

The Synechocystis sp PCC 6803 Oxa1 Homolog Is Essential for Membrane Integration of Reaction Center Precursor Protein pD1

“…The degree of photoinhibition in vivo reflects the level of equilibrium between PSII photodamage and PSII repair. If the repair process is inhibited or too slow relative to the damage rate, photodamaged PSII accumulates, leading to slower or completely stopped growth (Allakhverdiev et al, 2005). At light intensities up to 100 mmolÁm ÿ2 Ás ÿ1 , the rate of photodamage is balanced by the fast repair of PSII.…”

“…At light intensities up to 100 mmolÁm ÿ2 Ás ÿ1 , the rate of photodamage is balanced by the fast repair of PSII. Significant photoinhibition in higher plants becomes obvious at high light intensities of 1500 to 2000 mmolÁm ÿ2 Ás ÿ1 , which is thus widely used as the light intensity for the in vivo analysis of photoinhibition (Trebst et al, 2002;Allakhverdiev et al, 2005;Hakala et al, 2005). Therefore, the growth defect of slr1471-gfp at light intensities of 40 to 80 mmolÁm ÿ2 Ás ÿ1 is remarkable.…”

Regulation of Translation by the Redox State of Elongation Factor G in the Cyanobacterium Synechocystis sp. PCC 6803

“…Synthesis of the D1 protein is induced by light at the translational level in plants (36,37) and algae (38) and at both the transcriptional and the translational level in cyanobacteria (39,40). In addition, the activation of the synthesis of the D1 protein requires reducing power derived from the photosynthetic transport of electrons (41)(42)(43).…”

The Solar Action Spectrum of Photosystem II Damage

“…lincomycin or chloramphenicol) is directly proportional to the intensity of light (Mattoo et al, 1984; Tyystjärvi and Aro, 1996;Nishiyama et al, 2001Nishiyama et al, , 2004Allakhverdiev and Murata, 2004;Chow et al, 2005). Furthermore, recent studies have demonstrated that interruption of the Calvin cycle (Hakala et al, 2005;Takahashi and Murata, 2005;Takahashi et al, 2007) and inhibition of electron transfer between Q A and Q B (Jegerschö ld et al, 1990;Kirilovsky et al, 1994;Allakhverdiev et al, 2005) have no effect on the rate of photodamage to PSII, but in fact cause inhibition of the repair of photodamaged PSII due to suppression of the de novo synthesis of PSII proteins Murata, 2005, 2006). Thus, photodamage to PSII is paradoxically not associated with the excess light absorbed by photosynthetic pigments Murata et al, 2007;Takahashi and Murata, 2008).…”