THE PHOTOSYNTHETIC APPARATUS OF Acetabularia mediterranea GROWN UNDER RED OR BLUE LIGHT. BIOPHYSICAL QUANTIFICATION and CHARACTERIZATION OF PHOTOSYSTEM II and ITS CORE COMPONENTS

Abstract

The photosynthetic activity of white light-grown Acerabularia mediterranea Lamouroux (= A. acetabulum ( L . ) Silva) decreases under continuous red light to less than 20"/0 within 3 weeks. Subsequent blue light reactivates photosynthesis within a relatively short period of 3 days. In a former publication (Wennicke and Schmid, Planr Physiol. 84, [1252][1253][1254][1255][1256] 1987) we have shown that the regulated rate limiting step, which is an immediate light driven reaction, is part of photosystem I1 (PS 11). The following biophysical properties of PS I1 were analyzed in thylakoids isolated from algae grown 3 weeks under either blue or red light with or without subsequent 3 days of blue light illumination: (a) fluorescence induction in the short time domain dominated by QA reduction. (b) the slow fluorescence decline reflecting pheophytin photoaccumulation, (c) absorption changes at 320 and 830 nm under repetitive flash excitation as indicator for the turnover of Q, and P,,,,, respectively, (d) oscillation pattern of the oxygen yield by a flash train in dark adapted samples and (e) the binding capacity for atrazine. None of these PS I1 functions were severely affected, but a minor impairment of 2&30% was observed in the thylakoids from algae grown for 3 weeks in red irradiation. The changes d o not fully account for the drastic reduction of the electron transport through PS I1 which was 80% after red light treatment. Therefore, the regulated rate-limiting step appears to not be mainly located in the PS I1 core complex itself. It seems likely that the regulation process predominantly comprises the antenna system.

Quantitative correlation of peripheral and intrinsic core polypeptides of photosystem II with photosynthetic electron-transport activity ofAcetabularia mediterranea in red and blue light

“…However, as the blue-light-dependent changes in the electron-transport system were mainly confined to PSII (Wennicke and Schmid 1987), special attention was paid to polypeptides which were components of this photosynthetic complex: the chlorophyllproteins of the major light-harvesting complex, the two Chl a-proteins CP43 and CP47, the reaction-centre core polypeptides D1 and D2 and the extrinsic proteins of the water-splitting enzyme. In accordance with the fluorescence-induction properties of isolated thylakoids (Schmid et al 1990), no quantitative changes at all were found in the LHCP complex (Figs. 3, 4, 7).…”

“…The rate-limiting step which is under regulation takes part in primary light energy conversion since curves of photosynthesis versus irradiance differ also in their light-limited regions (Wennicke and Schmid 1987). Recent biophysical analysis (Schmid et al 1990) has shown that the function of the PSII reaction centre is not qualitatively affected. Quantitative alterations of the PSII centre functions, found within three weeks of red-light irradiation, were in the order of less than 30%, thus being too small to account fully for an overall change of PSII activity (and total photosynthetic activity) of more than 80%.…”

“…This suspension was used for the isolation of chloroplast membranes as described by Apel et al (1975). Recently, we changed to a different preparation protocol (Schmid et al 1990) which yields a higher amount of cytoplasm-free chloroplasts and eliminates bacteria that are associated with the cell walls of the Aeetabularia cultures used.…”

“…The component participates in the light-dependent processes of PSII (Wennicke and Schmid 1987). Recent biophysi-cal analysis (Schmid et al 1990) indicated that the quantitative changes in the function of components of the PSII reaction-centre core are only in the range of 20-30% and thus are insufficient to fully explain the large changes of total PSII activity. As we were interested in the molecular changes that are responsible for the changes of photosynthetic activity in vivo under red and blue light, the investigations of the present paper were intended to analyze the quantity of polypeptides in the photosynthetic membrane under these conditions.…”

Photoreceptors in Algae

“…Blue light induction has been shown for the enzyme carbonic anhydrase (Dionisio et al, 1989), for photosynthesis (Dring, 1989;Schmid et al, 1990;Schmid, 1991), and for nitrate and nitrite uptake (Aparicio and Quiiiones, 1991) in several green and brown algae. Growth of Chlorella hessleri under blue light leads to smaller species of phosphofructokinase (360 and 760 kDA) than growth under R (1.580 kDA species) (Kowallik et al, 1990).…”