Shortening of life-time of the pair [P680+Pheo-] contributes to general inhibitory effect of dinoseb on electron transfer in PS-II.
It is shown that dinoseb, added to subchloroplast photosystem-II (PS-II) preparations from pea at a concentration higher than 5 microM, along with blocking the electron transfer on the acceptor side of PS-II, induces the following effects revealing its capability to have redox interaction with the components of PS-II reaction center (RC)-pheophytin (Pheo) and chlorophyll P680: (1) acceleration of the dark relaxation of absorbance (delta A) and chlorophyll fluorescence (delta F) changes related to photoreduction of Pheo as a result of the photoreaction [P680Pheo] [symbol: see text] [P680Pheo-] that leads to elimination of the delta A and delta F at a concentration of the inhibitor higher than 50 microM; (2) lowering of the maximum level of fluorescence (F) due to a decrease of delta F under the condition when the electron acceptor, QA, is reduced; (3) loss of the described effects of dinoseb and appearance of its capability to donate electron to RC of PS-II in the presence of dithionite which reduces dinoseb in the dark; (4) inhibition of delta A related to photooxidation of P680; (5) activation of delta A related to photooxidation P700 in photosystem-I (PS-I) preparations (a similar effect is observed upon the addition of 0.2 mM methylviologen). It is suggested that redox interaction with the pair [P680+Pheo-] leading to the shortening of its life-time contributes to the general effect of inhibition of electron transfer in PS-II by dinoseb.
Vyacheslav
K
K
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142292, Russian Federation. Klimov@issp.serpukhov.su
Suleyman
A
A
Serguei
Z
Z
D019297:2,4-Dinitrophenol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D006540:Herbicides / Q000494:pharmacology*; D045342:Light-Harvesting Protein Complexes; D018532:Pisum sativum / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex
D006540:Herbicides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D019297:2,4-Dinitrophenol; C018527:dinoseb