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LIGHT‐INDUCED OIL GLOBULE MIGRATION IN HAEMATOCOCCUS PLUVIALIS (CHLOROPHYCEAE)
Author(s) -
Peled Ehud,
Pick Uri,
Zarka Aliza,
Shimoni Eyal,
Leu Stefan,
Boussiba Sammy
Publication year - 2012
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2012.01210.x
Subject(s) - biology , haematococcus pluvialis , chloroplast , cytochalasin b , biophysics , cytoplasm , phalloidin , endoplasmic reticulum , microfilament , microbiology and biotechnology , biochemistry , cytoskeleton , astaxanthin , cell , carotenoid , gene
Astaxanthin‐rich oil globules in H aematococcus pluvialis display rapid light‐induced peripheral migration that is unique to this organism and serves to protect the photosynthetic system from excessive light. We observed rapid light‐induced peripheral migration that is associated with chlorophyll fluorescence quenching, whereas the recovery was slow. A simple assay to follow globule migration, based on chlorophyll fluorescence level has been developed. Globule migration was induced by high intensity blue light, but not by high intensity red light. The electron transport inhibitor dichlorophenyl‐dimethylurea did not inhibit globule migration, whereas the quinone analog (dibromo‐methyl‐isopropylbenzoquinone), induced globule migration even at low light. Actin microfilament‐directed toxins, such as cytochalasin B and latrunculin A , inhibited the light‐induced globule migration, whereas toxins against microtubules were ineffective. Electron microscopic ( EM ) imaging confirmed the cytoplasmic localization and peripheral migration of globules upon exposure to very high light ( VHL ). Scanning EM of freeze‐fractured cells also revealed globules within cytoplasmic bridges traversing the chloroplast, presumably representing the pathway of migration. Close alignments of globules with endoplasmic reticulum ( ER ) membranes were also observed following VHL illumination. We propose that light‐induced globule migration is regulated by the redox state of the photosynthetic electron transport system. Possible mechanisms of actin‐based globule migration are discussed.