The chloride requirement for photosynthetic oxygen evolution. Analysis of the effects of chloride and other anions on amine inhibition of the oxygen-evolving complex

AbstractThe effects of short-term treatment with phenylurea (DCMU, isoproturon) and phenol-type (ioxynil) herbicides on the green algaChlorella kessleriand the cyanobacteriumSynechocystis salinawith different organizations of photosystem II (PSII) were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution measured by polarographic oxygen electrodes (Clark-type and Joliot-type). The photosynthetic oxygen evolution showed stronger inhibition than the PSII photochemistry. The effects of the studied herbicides on both algal and cyanobacterial cells decreased in the following order: DCMU>isoproturon>ioxynil. Furthermore, we observed that the number of blocked PSII centers increased significantly after DCMU treatment (204–250 times) and slightly after ioxynil treatment (19–35 times) in comparison with the control cells. This study suggests that the herbicides affect not only the acceptor side but also the donor side of PSII by modifications of the Mn cluster of the oxygen-evolving complex. We propose that one of the reasons for the different PSII inhibitions caused by herbicides is their influence, in different extents, on the kinetic parameters of the oxygen-evolving reactions (the initial S0−S1state distribution, the number of blocked centers SB, the turnover time of Sistates, misses and double hits). The relationship between the herbicide-induced inhibition and the changes in the kinetic parameters is discussed.

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Molecular evolutionary analysis of the psbP gene family of the photosystem II oxygen-evolving complex in Nicotiana

Genome ◽

10.1139/g93-066 ◽

1993 ◽

Vol 36 (3) ◽

pp. 483-488 ◽

Cited By ~ 8

Author(s):

Shao-Bing Hua ◽

Shyam K. Dube ◽

Shain-dow Kung

Keyword(s):

Molecular Evolution ◽

Photosystem Ii ◽

Gene Family ◽

Oxygen Evolution ◽

Oxygen Evolving Complex ◽

Photosynthetic Oxygen Evolution ◽

Evolutionary Analysis ◽

Protein Patterns ◽

Oxygen Evolving ◽

Molecular Evolutionary Analysis

Photosystem II psbP protein of the oxygen-evolving complex is involved in the photosynthetic oxygen evolution in plants. Four psbP polypeptides were detected in Nicotiana tabacum on a two-dimensional gel by immunostaining the proteins with antiserum against the pea psbP Comparison of the protein patterns of psbP from N. tabacum and its ancestral parents, N. sylvestris and N. tomentosiformis, indicated that each of the ancestral parents has contributed a pair of psbP proteins. This was supported by Southern hybridization results, which suggested that psbP in Nicotiana is encoded by a gene family consisting of four members in N. tabacum and two members each in N. glauca, N. langsdorffii, N. sylvestris, and N. tomentosiformis. A scheme of molecular evolution of the psbP genes in Nicotiana is also proposed.Key words: molecular evolution, Nicotiana, oxygen evolution, photosystem II.

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