Francis T. Haxo

CHLOROPLAST PIGMENT PATTERNS IN DINOFLAGELLATES1

The chlorophylls and carotenoids of 22 species of dinoflagellates were analysed by thin layer chromatography, using 2‐dimensional sucrose plates, and 1‐dimensional polyethylene plates for chlorophylls c1 and c2. Peridinin was the major carotenoid in 19 of the species, while fucoxanthin was the major carotenoid in 3. In the peridinin‐containing species, 5 carotenoid fractions, constituting more than 95% of the total carotenoids, were always present. These were peridinin (± neo‐peridinin), averaging 64% of the total carotenoid, diadinoxanthin, dinoxanthin, β‐carotene and a polar, unidentified pink xanthophyll. Six other carotenoid fractions occurred in minor or trace quantities among the species, but were not identified. Two of these had, a wide distribution; the other 4 were restricted to one or 2 species. The chlorophyll content of the dinoflagellate cultures ranged from 1–141 μg chlorophyll a + c/106 cells, a pattern which was broadly correlated with cell size. In the peridinin‐containing species the ratio of chlorophyll a to c on a molar basis was approximately 2 (range 1.60–4.39); in the fucoxanthin‐containing species this ratio was approximately 4 (range 2.65–5.73). Both chlorophylls c1 and c2 occurred in the fucoxanthin‐containing dinoflagellates, and only chlorophyll c2 (one exception) occurred in the peridinin‐containing dinoflagellates. These patterns of chlorophyll c and major carotenoid correspond to patterns previously observed in the Pyrrhophyta and the Chrysophyta, suggesting different phylogenetic origins for the “dinoflagellate” chloroplasts.

Persistence of a Photosynthetic Rhythm in Enucleated Acetabularia.

The unicellular alga Acetabularia was found to show a diurnal rhythm in photosynthesis. This rhythm continued for at least three cycles in constant light and temperature, and hence can be considered endogenous. Plants from which the nucleus had been removed by severing the basal rhizoids showed no modification in the photosynthetic rhythm over a number of cycles. The nucleus is, therefore, not immediately essential for the maintenance of rhythmicity in Acetabularia. Conversely, a mechanism for sustaining time-keeping must exist in the cytoplasm.

Comparative studies of chromatographically separated phycoerythrins and phycocyanins.

Abstract 1. 1. The chromatographic method of Swingle and Tiselius has been successfully applied to the separation and recovery of the bile pigment chromoproteins of a variety of red and blue-green algae. 2. 2. In addition to the conventional R and C varieties of phycoerythrin and phycocyanin, several other chromoproteins were encountered. Representatives of both algal groups were found to contain, as a minor component, a blue proteinacious pigment, characterized by a single absorption maximum at 650 mμ. This chromoprotein is probably identical with Lembergs allophycocyanin but is considered to be a natural constituent rather than an artifact formed during extraction. Unusual two-peaked phycoerythrins (maxima at 542.5 and 565 mμ) were found in extracts of the blue-green algae Phormidium ectocarpi and Phormidium fragile. 3. 3. Phycoerythrin from the unicellular red alga Porphyridium cruentum was found to be distinct spectrally from both R- and C-phycoerythrin when all preparations were made at neutral or slightly acidic pH values. Under alkaline conditions of extraction (above pH 7.5), the phycocyanin content of Porphyridium cells is destroyed, and phycoerythrin with an altered spectrum is recovered. It is felt probable that Porphyridium phycoerythrin, isolated under the former conditions and characterized by a broadened single-peaked, instead of a sharp two- or three-peaked spectrum in the visible region, is the native pigment. The less abundant phycocyanin fraction of Porphyridium includes the “allophycocyanin” and a two-peaked pigment tentatively identified as R-phycocyanin.

Effects of growth irradiance on the photosynthetic action spectra of the marine dinoflagellate, Glenodinium sp.

SummaryWhole cell absorption curves of the marine dinoflagellate Glenodinium sp., cultured at irradiances of 250μW/cm2 (low light) and 2500μW/cm2 (high light), were measured and their difference spectrum determined. Absorption by low light grown cells exceeded that of high light grown cells throughout the visible spectrum by a factor which ranged from 2 to 4. The difference spectrum supported the view that increased pigmentation, resulting from low light conditions, was largely due to an increase in cell content of a peridinin-chlorophyll a-protein (PCP) and an unidentified chlorophyll a component of the chloroplast membrane. Photosynthetic action spectrum measurements indicated that chlorophyll a, peridinin, and very likely chlorophyll c, were effective light-harvesting pigments for photosynthesis in both high and low light grown cultures of Glenodinium sp. Comparison of action spectra and absorption spectra suggested that low light grown cells selectively increased cellular absorption in the 480 nm to 560 nm region, and effectively utilized this spectral region for the promotion of oxygen evolution.

PIGMENTS OF THE DINOFLAGELLATE PERIDINIUM BALTICUM AND ITS PHOTOSYNTHETIC ENDOSYMBIONT1

An examination of the pigments of the binucleate dinoflagellate Peridinium balticum (Levander) Lemmerman revealed the presence of chlorophylls a, c1 and c2 and the carotenoids: fucoxanthin (most abundant), diadinoxanthin, diatoxanthin, an unidentified fucoxanthin‐like xanthophyll, β‐carotene, γ‐carotene and astaxanthin. A comparison of the pigments of P. balticum and P. foliaceum (Stein) Biecheler, also a binucleate dinoflagellate, demonstrated similar compositions. However P. balticum lacked the β‐carotene precursors (e.g. phytoene) which accumulated outside the chloroplast in P. foliaceum. This study indicates that P. balticum and P. foliaceum are closely related; each species is a heterotrophic dinoflagellate with a photosynthetic endosymbiont taxonomically affiliated with the Chrysophyta (Chrysophyceae or Bacillariophyceae).

CHLOROPLAST PIGMENTS OF CHLOROMONADOPHYCEAE

The chloroplast pigments of 2 species of Chloro‐monadophyceae have been examined. Both Gonyo‐stomum semen and Vacuolaria virescens possessed only one chlorophyll, chlorophyll a. Gonyostomum contained 4 carotenoids, but not fucoxanthin and peridinin. Vacuolaria also possessed 4 carotenoids which have been identified as β‐carotene and the 3 xanthophylls commonly found in the Xanthophyceae (as represented by Tribonema aequale). These are antheraxanthin, lutein monoepoxide, and an hydroxy lutein monoepoxide‐like xanthophyll. The taxonomic significance of these findings, the first for the Chloromonadophyceae, is discussed.

Carotenoids of the Florida red tide dinoflagellate Karenia brevis

The red tide dinoflagellate Karenia brevis, formerly Gymnodinium breve, contained fucoxanthin, 19′-butanoyloxyfucoxanthin and 19’-hexanoyloxyfucoxanthin as carotenoid chemotaxonomic markers. In addition to β,e-carotene, β,β-carotene, diatoxanthin, diadinoxanthin and 19-hexanoyloxyparacentrone 3-acetate, the diester of gyroxanthin was also present. Pigment identities were established by both chromatographic (TLC and HPLC) and spectrometric (UV-vis, MS) methods, for the fucoxanthins also 1H NMR was applied. The similarity in carotenoid pigmentation between the three ichthyotoxic dinoflagellates K. brevis, Karenia mikimotoi and Karlodinium micrum is pointed out. In terms of the endosymbiont theory the carotenoid pigmentation supports the hypothesis that these three species may have acquired their chloroplasts from a prymnesiophycean endosymbiont.

Carotenoids of clam, coral and nudibranch zooxanthellae in aposymbiotic culture

Abstract The carotenoids of unialgal cultures originating from symbiotic zooxanthellae of two molluscan ( Tridacna crocea , a giant clam, and Pteraeolidia ianthine a nudibranch) and one cnidian ( Pseudopterogorgia bipinnata , a gorgonian coral) host have been analysed by HPLC or TLC procedures combined with several spectroscopic techniques including MS and NMR. A high total carotenoid content (0.45-0.63% of the dry wt) was obtained. The carotenoid pattern with C 37 -norcarotenoids (peridinin and pyrrhoxanthin) comprising around 80% of total carotenoids, and β,β-carotene (2%), the ailenic dinoxanthin (3–4%) and the acetylenic diatoxanthin (1–3%) and diadinoxanthin (7–9%) representing minor C 40 -carotenoids, corresponds to that of peridinin-producing free-living dinoflagellates. Supplementary 1 H NMR and 13 C NMR data are reported for peridinin and pyrrhoxanthin. A polar, minor carotenoid, P447, was partly characterized as containing a disaccharide glycosidically bound to an allenic carotenoid aglycone. Re-evaluation of previous reports suggests the wide-spread occurrence of related carotenoid disaccharides in Dinophyceae for which they are considered a new chemosystematic marker.