title: Two forms of phycobilisomes in the Antarctic red macroalga Palmaria decipiens (Palmariales, Florideophyceae).
abstract: The phycobilisomes (PBS), the light-harvesting antennae, from the endemic Antarctic red macroalga Palmaria decipiens were isolated on discontinuous sucrose gradients in two discrete bands and not in one as expected. To exclude methodical faults, we also isolated PBS from the temperate Palmaria palmata and the unicellular red algae Porphyridium cruentum and Rhodella violacea. In P. palmata the PBS were separated in two discrete bands, whereas the PBS from Porphyridium and Rhodella were found in one band. The double-banded PBS (PBSup and PBSlow) from P. decipiens were further characterized by absorption and fluorescence spectroscopy, native and SDS-PAGE as well as by negative staining. The phycobiliproteins RIII-phycoerythrin, RI-phycocyanin and allophycocyanin were identified and 3 gamma-subunits were described. The PBSup and PBSlow showed no significant differences in their absorption spectra and phycobiliprotein ratios although the negative stained PBSlow were smaller. Differences were found in their low molecular mass subunit complexes, which are assumed to be r-phycoerythrin. The polypeptide pattern of the PBSup and PBSlow showed no differences in the molecular masses of their subunits and linker polypeptides, but in their percentage distribution. The results suggest that the PBSlow is a closer packed and PBSup a little more loosely aggregated hemiellipsiodal PBS form. We discuss the ecophysiological function of two PBS forms in P. decipiens and suggest advantages in the rapid acclimation to changes in environmental light conditions.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany; Institute of Cell Biology, Biochemistry and Biotechnology, University of Bremen, P.O. Box 33 04 40, D-28334 Bremen, Germany; Present address: Department of Plant Biology, Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Denmark.
authors.forename: Ulrike H.
authors.initials: UH
authors.lastname: Lüder
authors.forename: Jürgen
authors.initials: J
authors.lastname: Knoetzel
authors.forename: Christian
authors.initials: C
authors.lastname: Wiencke