Quantitative correlation of peripheral and intrinsic core polypeptides of photosystem II with photosynthetic electron-transport activity ofAcetabularia mediterranea in red and blue light |
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Authors: | Rainer Schmid Rainer Wennicke Sigrun Fleischhauer |
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Institution: | 1. Institut für Pflanzenphysiologie, Zellbiologie und Mikrobiologie, Freie Universit?t Berlin, K?nigin-Luise-Stra?e 12-16, 1000, Berlin
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Abstract: | The high photosynthetic activity (O2 production and CO2 consumption) ofAcetabularia mediterranea Lamour. (=A. acetabulum (L.) Silva) characteristic of cells cultured in white light decreases slowly when cells are kept in continuous red light,
and is less than 20% of the original activity after three weeks. Subsequent blue irradiation restores the original activity
completely within 3–5 d. The polypeptide composition of the thylakoids from cells grown in either red or blue light and after
transfer from red to blue light was analyzed mainly with regards to photosystem II (PSII). The P700-containing reaction-centre
complex of photosystem I, CPI, showed only minor quantitative alterations as a consequence of the growth-light quality, which
correlated well with the activity of photosystem I under these conditions. In PSII, no drastic changes occurred in the quantity
of the reaction-centre components D1 (herbicide-binding polypeptide) and D2, as determined by immunoblots. Likewise, the proteins
associated with the water-splitting apparatus did not change detectably in thylakoids from red- or blue-light-treated cells
(the 16-kDa component could not be found inAcetabularia thylakoids). The level of the major light-harvesting complex was completely unaffected by the light quality. In contrast,
the quantities of the chlorophyll a-protein complexes of the core antenna, CP43 and CP47 (and probably CP29), changed, with
kinetics similar to those of total photosynthetic activity. We postulate that the function of the PSII antenna became increasingly
impaired in the absence of blue light (i.e. in red light), while blue light had a restoring effect. The peripheral antenna,
comprising the light-harvesting complexes, is probably functionally connected with the reaction-centre chlorophylls via the
core antenna chlorophyll-protein complexes (CP43, CP47 and probably CP29). A deficiency of these complexes would lead to uncoupling
of antenna and reaction centre in the majority of PSII complexes after long periods of red-light treatment. |
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Keywords: | Acetabularia Blue light Chlorophyll-protein complexes Photosystem II (antenna function) Thylakoid (polypeptide composition) |
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