CYTOCHROME-F LOSS IN ASTAXANTHIN-ACCUMULATING RED-CELLS OF HAEMATOCOCCUS-PLUVIALIS (CHLOROPHYCEAE) - COMPARISON OF PHOTOSYNTHETIC ACTIVITY,PHOTOSYNTHETIC ENZYMES, AND THYLAKOID MEMBRANE POLYPEPTIDES IN RED AND GREEN CELLS

Photosynthetic activity, chloroplast enzymes, and polypeptides were co mpared in green and red (ketocarotenoid-containing) cultures of the mi croalga Haematococcus pluvialis Flotow. Green cultures, grown at 80 mu mol photons . m(-2) . s(-1) in an acetate-containing medium, had a me an generation time of 27 h. Ketocarotenoid accumulation was induced by transfer of green cultures to PO4-deficient medium and exposure to 25 0 mu mol photons . m(-2) . s(-1). Under these conditions, there was no increase in cell number, and the cultures turned red. Relative amount s of enzymes and thylakoid polypeptides in red and green cells were as certained by immunoprobing with standardization on a chlorophyll (Chi) basis. In red cultures, the label of cytochrome f was greatly decreas ed (< 1% of green cell level), which is expected to greatly impair the linear electron flow from photosystem (PS)II to PS I. Also, the level s of apoproteins in red cells, namely, of CPI, D2, CP47, LHC I, and ri bulose-1,5-bisphosphate carboxylase were reduced to 15, 18, 29 48, and 80%, respectively, of those in green cells. Only adenosine triphospha te synthase exhibited no significant change in the two types of cultur es. The respiration rate of red cultures was much higher (100 mu moles O-2 . mg Chl(-1) . h(-1) than that of green cells (16 mu moles O-2 . mg . Chl(-1) . h(-1)). Conversely, net O-2 evolution (at P-max) in gre en cultures was 80 mu moles O-2 . mg Chl(-1) . h(-1) but was -40 mu mo les O-2 . mg . Chl(-1) . h(-1) in red cultures. PS II activity was dem onstrated in broken cells of both green and red cultures, showing acti vity of 40 and 15 mu moles DCPIP . mg Chl(-1) . h(-1) (with DPC as ele ctron donor), respectively. In contrast, PS I activity measured by the Mehler reaction showed that red rather than green cells had a greater activity (64 vs. 46 mu moles O-2 mg . Chl(-1) . h(-1), respectively). Thus, in spite of the decline of O-2 evolution in red cells, the phot osystems were still functional. We postulate that the decline of O-2 e volution in red cells is largely attributable to an increase in the re spiration rate and the impairment of linear electron flow from PS II t o PS I and, to some extent, to a decrease in components of the photosy stems.