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Titolo:
DYNAMIC-RESPONSES OF PHOTOSYSTEM-II AND PHYCOBILISOMES TO CHANGING LIGHT IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC-7942
Autore:
CLARKE AK; CAMPBELL D; GUSTAFSSON P; OQUIST G;
Indirizzi:
UMEA UNIV,DEPT PLANT PHYSIOL S-90187 UMEA SWEDEN
Titolo Testata:
Planta
fascicolo: 3, volume: 197, anno: 1995,
pagine: 553 - 562
SICI:
0032-0935(1995)197:3<553:DOPAPT>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
SP STRAIN PCC-7942; PSBA GENE FAMILY; ANACYSTIS-NIDULANS; CHLOROPHYLL FLUORESCENCE; REGULATED EXPRESSION; REACTION CENTERS; DISTINCT FORMS; PHOTOINHIBITION; PHOTOSYNTHESIS; PROTEIN;
Keywords:
ACCLIMATION; D1 TURNOVER; PHOTOSYSTEM II; PHYCOBILISOME; SYNECHOCOCCUS SP PCC 7942; VARIABLE LIGHT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
44
Recensione:
Indirizzi per estratti:
Citazione:
A.K. Clarke et al., "DYNAMIC-RESPONSES OF PHOTOSYSTEM-II AND PHYCOBILISOMES TO CHANGING LIGHT IN THE CYANOBACTERIUM SYNECHOCOCCUS SP PCC-7942", Planta, 197(3), 1995, pp. 553-562

Abstract

We have examined the molecular and photosynthetic responses of a planktonic cyanobacterium to shifts in light intensity over periods up to one generation (7 h). Synechococcus sp. PCC 7942 possesses two functionally distinct forms of the D1 protein, D1:1 and D1:2. Photosystem II (PSII) centers containing D1:1 are less efficient and more susceptibleto photoinhibition than are centers containing D1:2, Under 50 mu mol photons m(-2). s(-1), PSII centers contain D1:1, but upon shifts to higher light (200 to 1000 mu mol photons m(-2). s(-1)), D1:1 is rapidly replaced by D1:2, with the rate of interchange dependent on the magnitude of the light shift. This interchange is readily reversed when cells are returned to 50 mu mol photons m(-2). s(-1). If, however, incubation under 200 mu mol photons m(-2). s(-1) is extended, D1:1 content recovers and by 3 h after the light shift D1:1 once again predominates. Oxygen evolution and chlorophyll (Chi) fluorescence measurements spanning the light shift and D1 interchanges showed an initial inhibition of photosynthesis at 200 mu mol photons m(-2). s(-1), which correlates with a proportional loss of total D1 protein and a cessation of growth. This was followed by recovery in photosynthesis and growth as the maximum level of D1:2 is reached after 2 h at 200 mu mol photons m(-2). s(-1) Thereafter, photosynthesis steadily declines with the loss of D1:2 and the return of the less-efficient D1:1. During the D1:1/D1:2 interchanges, no significant change occurs in the level of phycocyanin (PC) and Chl a, nor of the phycobilisome rod linkers. Nevertheless, the initial PC/Chl a ratio strongly influences the magnitude of photoinhibition and recovery during the light shifts. In Synechococcus sp. PCC 7942, the PC/Chl a ratio responds only slowly to light intensity or quality, while the rapid but transient interchange between D1:1 and D1:2 modulates PSII activity to limit damage upon exposure to excess light.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 27/11/20 alle ore 13:42:11