Light-dependent D1 protein synthesis and translocation is regulated by reaction center II. Reaction center II serves as an acceptor for the D1 precursor.

Photoinhibitory performance and its physiological basis have been studied in Oryza sativa L. subspecies indica and japonica, and their reciprocal F1 hybrids. The results demonstrate that the japonica ssp. was usually more tolerant to photoinhibition, indicated by higher maintaining capacity of D1 protein (less degradation), higher induced superoxide dismutase (SOD) activity and longer duration of the activity. Compared with japonica, the indica ssp. was more sensitive to photoinhibition, and exhibited more degradation of D1 protein and a much larger xanthophyll pool. A statistically significant positive correlation exists between D1 protein content and Fv/Fm, PSII activity and Pn during photoinhibition (r2 = 0.98, 0.93, 0.95, respectively, P < 0.01). This result further supported the hypothesis that D1 protein encoded by plastid genes might play an important physiological role in the mechanism of photoinhibition. This hypothesis is also enhanced by the fact that the capacity of D1 protein synthesis mediated the components and cycle of xanthophyll and non-photochemical quenching in treatment with streptomycin, a D1 protein synthesis inhibitor, while the xanthophyll cycle had a photoprotective role for D1 protein and Fv/Fm in treatment with DDT, a xanthophyll cycle inhibitor. The photoinhibition of reciprocal F1 hybrids between japonica and indica is mainly intermediate, but somewhat inclined to the maternal line. This demonstrates that the basic feature of photoinhibition was controlled by the interaction of an intrinsic factor, D1 protein encoded by plastid genes, with the xanthophyll cycle, as well as SOD, controlled by nuclear genes. Since the response to photoinhibitory treatment of indica–japonica F1 hybrids seems to depend on female parents, we propose to select and use photoinhibition-tolerant varieties as female parents for generation of photoinhibition-tolerant hybrids.

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Recovery of the photosynthetic apparatus from photoinhibition during dark incubation of the green alga Dunaliella salina

Functional Plant Biology ◽

10.1071/pp99004 ◽

1999 ◽

Vol 26 (7) ◽

pp. 679 ◽

Cited By ~ 5

Author(s):

Jürgen E. W. Polle ◽

Anastasios Melis

Keyword(s):

Reaction Center ◽

Dunaliella Salina ◽

De Novo ◽

Light Harvesting ◽

Photosynthetic Apparatus ◽

D1 Protein ◽

Dark Incubation ◽

Chl A ◽

Lag Period ◽

Stressed Cells

The light-independent recovery of the photosynthetic apparatus from photoinhibition was monitored upon a transition of irradiance-stressed Dunaliella salina Teod. to darkness. Upon dark incubation, the chlorophyll (Chl) a /Chl b ratio of the cells decreased promptly with a half-time of 2.5 h from about 12:1 to about 5:1. In contrast, dark incubation of control cells resulted in only a negligible change of the Chl a /Chl b ratio. During dark incubation of irradiance-stressed cells, the level of the Chl a and b light-harvesting proteins of photosystem II (PSII) increased, a change accompanied by alterations in the composition of these light-harvesting proteins. The amount of photodamaged PSII, measured from the relative amount of a 160 kDa protein complex which contains the photodamaged D1 reaction center protein, decreased during dark incubation after an initial lag period. Concomitantly, the amount of functional PSII, measured from the 32 kDa form of D1, increased slightly in the dark. The results show that, in the dark, photodamaged D1 is slowly removed upon degradation from the thylakoid membrane and replaced by a de novo synthesized D1 protein. The amount of reaction center proteins and number of photochemically active PSI centers increased in the dark. These results suggest that thylakoid membranes of irradiance-stressed D. salina exist in a state of dynamic flux. We conclude that several aspects of the D. salina recovery from photoinhibition are light independent.

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