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
S. Tan et al., 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, Journal of phycology, 31(6), 1995, pp. 897-905
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.