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Characterization of the heat‐induced stimulation of Photosystem‐I‐mediated electron transport
Author(s) -
SAYED OSAMA H.,
EARNSHAW MICHAEL J.,
EMES MICHAEL J.
Publication year - 1994
Publication title -
acta botanica neerlandica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0044-5983
DOI - 10.1111/j.1438-8677.1994.tb00741.x
Subject(s) - thylakoid , electron transport chain , stimulation , photosystem i , photosystem ii , biophysics , chemistry , carbodiimide , electron acceptor , electron transfer , chloroplast , photochemistry , photosynthesis , biochemistry , biology , neuroscience , gene
SUMMARY Uncoupled Photosystem I (PS I) activity driven by either reduced 2,6‐dichlorophenolindophenol (DCPIPH 2 ) or N,N,N',N'‐tetramethyl‐p‐phenylene diamine (TMPDH 2 ) showed a stimulation following pre‐treatment at 40–50°C, followed by inhibition at higher temperatures. The stimulation was more marked in thylakoids isolated from warm‐grown plants than in those isolated from cool‐grown plants. Approximately maximal rates of PS I activity were achieved at physiological temperatures (25–35°C) using highly lipophilic‐reduced diaminodurene (DADH 2 ) as an electron donor with little stimulation occurring as a result of high temperature pre‐treatment. Electron transport driven by all three electron donors was markedly inhibited by KCN/HgCl 2 following all pre‐treatment temperatures, but relatively insensitive to ethyldimethylaminopropyl‐carbodiimide (EDAC). It is suggested that the stimulation of PS I activity involves a phase change in the thylakoid membrane leading to an increase in permeability which allows enhanced access of DCPIPH 2 and TMPDH 2 to a common electron acceptor site located in the region of cytochrome f. The greater stimulation of electron transport in thylakoids isolated from warm‐grown plants may be due to a more pronounced phase change occurring as a consequence of altered membrane composition as modified by growth temperature.