ON THE LONG-WAVELENGTH SPECTRAL FORMS OF CHLOROPHYLL-A IN PHOTOSYSTEM-I - SPECTROSCOPIC AND IMMUNOLOGICAL INVESTIGATIONS ON A GREENING MUTANT OF THE GREEN-ALGA SCENEDESMUS-OBLIQUUS
H. Schiller et al., ON THE LONG-WAVELENGTH SPECTRAL FORMS OF CHLOROPHYLL-A IN PHOTOSYSTEM-I - SPECTROSCOPIC AND IMMUNOLOGICAL INVESTIGATIONS ON A GREENING MUTANT OF THE GREEN-ALGA SCENEDESMUS-OBLIQUUS, Photosynthesis research, 55(1), 1998, pp. 95-107
The origin of the long-wavelength chlorophyll(Chl) absorption (lambda(
peak) > 680 nm) and fluorescence emission (lambda(peak) > 685 nm) has
been investigated on Scenedesmus mutants (C-2A'-series, lacking the ab
ility to synthesize chlorophyll in the dark) grown at 0.3 (LL), 10 (ML
) and 240 mu E s(-1) m(-2) (HL). LL cells are arrested in an early gre
ening state; consequently, 'Chl availability' determines the phenotype
. LL thylakoids are totally lacking long-wavelength Chl; nonetheless,
PS I and PS II are fully functional. Gel electrophoresis and Western b
lots indicate that four out of seven resolved LHC polypeptides seem to
require a high Chi availability for assembly of functional chlorophyl
l-protein complexes. The PS I core-complex of ML and HL thylakoids con
tains long-wavelength chlorophylls, but in the PS I core-complex of LL
thylakoids these pigments are lacking. We conclude that long-waveleng
th pigments are only present in the PS I core in the case of high Chl
availability. The following hypothesis is discussed: Chl availability
determines not only the LHC polypeptide pattern, but also the number o
f bound Chl molecules per individual pigment-protein complex. Chl-bind
ing at non-obligatory, peripheral sites of the pigment-protein complex
results in long-wavelength Chl. In the case of low Chl availability,
these sites are not occupied and, therefore, the long-wavelength Chl i
s absent.