Peridinin-chlorophyll A-proteins Research Articles

Peridinin-chlorophyll-protein complex industry from algae: A critical review of the current advancements, hurdles, and biotechnological potential

PCPs (Peridinin-chlorophyll a-proteins), water-soluble light-harvesting complexes only found in dinoflagellates, have achieved tremendous research progress in the past few decades. Their commercial form product, Peridinin-chlorophyll-protein complex, is enormously applied in fluorescent label probes because of unique fluorescence characteristic. The huge application prospect has spawned a large number of studies on PCPs. Most of the research has been carried out around the light factor, however, other factors and the regulatory mechanism of PCPs are still indistinct. Although the complete nucleic acid sequences, vivid protein structures and explicit energy transfer mechanism of some PCPs have been revealed, that of PCPs in other dinoflagellates are not yet clear, which are the trends in future. It is not difficult to realize the crude purification of PCPs, but pioneering new ways and obtaining high-purity PCPs are still difficulties. Many applications of PCPs have been developed, nevertheless, plenty of which are in the laboratory stage. Due to the variety of research results of PCPs but lack of systematic summary, we carefully review the recent information about PCPs in fields of PCP-producing algae species, metabolic regulation, structure, energy transfer and photoprotection. Moreover, we further highlight purification processes and potential applications of PCPs. Finally, the challenges and strategies of large-scale commercial and cross-domain applications of PCPs are also analyzed and assessed.

Upregulation of Peridinin-Chlorophyll A-Binding Protein in a Toxic Strain of Prorocentrum hoffmannianum under Normal and Phosphate-Depleted Conditions.

Some strains of the dinoflagellate species Prorocentrum hoffmannianum show contrasting ability to produce diarrhetic shellfish poisoning (DSP) toxins. We previously compared the okadaic acid (OA) production level between a highly toxic strain (CCMP2804) and a non-toxic strain (CCMP683) of P. hoffmannianum and revealed that the cellular concentration of OA in CCMP2804 would increase significantly under the depletion of phosphate. To understand the molecular mechanisms, here, we compared and analyzed the proteome changes of both strains growing under normal condition and at phosphate depletion using two-dimensional gel electrophoresis (2-DE). There were 41 and 33 differential protein spots observed under normal condition and phosphate depletion, respectively, of which most were upregulated in CCMP2804 and 22 were common to both conditions. Due to the lack of matched peptide mass fingerprints in the database, de novo peptide sequencing was applied to identify the differentially expressed proteins. Of those upregulated spots in CCMP2804, nearly 60% were identified as peridinin-chlorophyll a-binding protein (PCP), an important light-harvesting protein for photosynthesis in dinoflagellates. We postulated that the high expression of PCP encourages the production of DSP toxins by enhancing the yields of raw materials such as acetate, glycolate and glycine. Other possible mechanisms of toxicity related to PCP might be through triggering the transcription of non-ribosomal peptide synthetase/polyketide synthase genes and the transportation of dinophysistoxin-4 from chloroplast to vacuoles.

Characterisation and Bioactivity Analysis of Peridinin-Chlorophyll a-Protein (PCP) Isolated from Symbiodinium tridacnidorum CS-73

Peridinin-Chlorophyll a-Proteins (PCP) are the major light harvesting proteins in photosynthetic dinoflagellates. PCP shows great variation in protein length, pigment ratio, sequence, and spectroscopic properties. PCP conjugates (PerCP) are widely used as fluorescent probes for cellular and tissue analysis in the biomedical field. PCP consists of a peridinin carotenoid; thereby, it can potentially be used as a bioactive compound in pharmaceutical applications. However, the biological activities of PCP are yet to be explored. In this study, we extracted, purified, and partially characterised the PCP from Symbiodinium tridacnidorum (CS-73) and explored its antioxidant, anti-cancer and anti-inflammation bioactivities. The PCP was purified using an ÄKTA™ PURE system and predicted to be of 17.3 kDa molecular weight (confirmed as a single band on SDS-PAGE) with an isoelectric point (pI) 5.6. LC-MS/MS and bioinformatic analysis of purified PCP digested with trypsin indicated it was 164 amino acids long with >90% sequence similarity to PCP of SymA3.s6014_g3 (belonging to clade A of Symbiodinium sp.) confirmed with 59 peptide combinations matched across its protein sequence. The spectroscopic properties of purified PCP showed a slight shift in absorption and emission spectra to previously documented analysis in Symbiodinium species possibly due to variation in amino acid sequences that interact with chl a and peridinin. Purified PCP consisted of a 19-amino-acid-long signal peptide at its N terminal and nine helixes in its secondary structure, with several protein binding sites and no DNA/RNA binding site. Furthermore, purified PCP exhibited antioxidant and in vitro anti-inflammation bioactivities, and anti-cancer activities against human metastatic breast adenocarcinoma (MDA-MB-231) and human colorectal (HTC-15) cancer cell lines. Together, all these findings present PCP as a promising candidate for continued investigations for pharmaceutical applications to cure chronic diseases, apart from its existing application as a fluorescent-probe.

Methylation Pattern and Expression Dynamics of Methylase and Photosystem Genes Under varying light Intensities in Fugacium kawagutii (Symbiodiniaceae).

Previous studies have documented extensive methylation of CpG islands and abundant methyltransferase gene (DNMT) in Fugacium kawagutii (formerly Symbiodinium kawagutii) genome. However, whether DNA methylation plays a role in regulating gene expression in this and other dinoflagellates remains unclear. Here, we characterized gene body methylation levels using methylation-specific PCR (MS-PCR) and bisulfite sequencing PCR (BSP) and measured transcriptional levels for three photosystem genes in F. kawagutii under different light conditions (20, 100, and 600µE·m-2 ·s-1 ). To explore the association of methylation with DNA methylase, the expression of DNA methyltransferase (Symbio-DIRS-Dnmt3) was also measured. Our results showed that peridinin-chlorophyll a-binding protein (PCP), light-harvesting complex (LHC), and chlorophyll a-c-binding protein complex (acpPC) gene expression was all significantly up-regulated under low light in which their methylation level was down-regulated, constant, and elevated, respectively. Symbio-DIRS-Dnmt3 exhibited elevated transcriptional level under increased light intensity. The results led us to hypothesize that DNA methylation level can be modulated by environmental conditions such as irradiance, probably through the regulation of Symbio-DIRS-Dnmt3 transcription level, and in turn may regulate the expression of genes in F. kawagutii. Further study is needed to determine whether the same gene methylation and expression characteristics reported here occur in other dinoflagellates and to explore their ecological implications.

Metaproteomics reveals metabolic transitions between healthy and diseased stony coral Mussismilia braziliensis.

Infectious diseases such as white plague syndrome (WPS) and black band disease (BBD) have caused massive coral loss worldwide. We performed a metaproteomic study on the Abrolhos coral Mussismilia braziliensis to define the types of proteins expressed in healthy corals compared to WPS- and BBD-affected corals. A total of 6363 MS/MS spectra were identified as 361 different proteins. Healthy corals had a set of proteins that may be considered markers of holobiont homoeostasis, including tubulin, histone, Rab family, ribosomal, peridinin-chlorophyll a-binding protein, F0F1-type ATP synthase, alpha-iG protein, calmodulin and ADP-ribosylation factor. Cnidaria proteins found in healthy M.braziliensis were associated with Cnidaria-Symbiodinium endosymbiosis and included chaperones (hsp70, hsp90 and calreticulin), structural and membrane modelling proteins (actin) and proteins with functions related to intracellular vesicular traffic (Rab7 and ADP-ribosylation factor 1) and signal transduction (14-3-3 protein and calmodulin). WPS resulted in a clear shift in the predominance of proteins, from those related to aerobic nitrogen-fixing bacteria (i.e. Rhizobiales, Sphingomonadales and Actinomycetales) in healthy corals to those produced by facultative/anaerobic sulphate-reducing bacteria (i.e. Enterobacteriales, Alteromonadales, Clostridiales and Bacteroidetes) in WPS corals. BBD corals developed a diverse community dominated by cyanobacteria and sulphur cycle bacteria. Hsp60, hsp90 and adenosylhomocysteinase proteins were produced mainly by cyanobacteria in BBD corals, which is consistent with elevated oxidative stress in hydrogen sulphide- and cyanotoxin-rich environments. This study demonstrates the usefulness of metaproteomics for gaining better comprehension of coral metabolic status in health and disease, especially in reef systems such as the Abrolhos that are suffering from the increase in global and local threatening events.

Assignment of IR bands of isolated and protein-bound Peridinin in its fundamental and triplet state by static FTIR, time-resolved step-scan FTIR and DFT calculations

The vibrational properties of Peridinin in its fundamental state and in the excited triplet state have been investigated by DFT calculations and static and time-resolved FTIR spectroscopy. The infrared spectrum of Peridinin in its fundamental state has been explored in the whole 2000–600cm−1 range, and interpreted in term of molecular vibrations. In particular, new infrared bands have been identified and assigned to specific molecular vibrations. 3Peridinin molecular vibrations have also been investigated by DFT calculations. In addition, putative IR bands belonging to Peridinin and 3Peridinin have been identified in the step-scan FTIR difference spectrum of the Peridinin–Chlorophyll a–Protein from Amphidinium carterae, where light induce formation of a triplet state localized on one or more Peridinins. The exact nature of the triplet state formed in Peridinin–Chlorophyll a–Protein from dinoflagellates, in particular the possible involvement in this triplet state of 3Chlorophyll a, has been largely debated in the last few years (see Carbonera et al., 2014 [3]); time-resolved differential FTIR experiments have played a key role in this debate. Identification of IR marker bands for the main molecule (Peridinin) implicated in this photophysical process is therefore particularly important and makes this study a significant step towards the full understanding of Peridinin–Chlorophyll-a–Proteins photophysics.

Separate introns gained within short and long soluble peridinin-chlorophyll a-protein genes during radiation of Symbiodinium (Dinophyceae) clade A and B lineages.

Here we document introns in two Symbiodinium clades that were most likely gained following divergence of this genus from other peridinin-containing dinoflagellate lineages. Soluble peridinin-chlorophyll a-proteins (sPCP) occur in short and long forms in different species. Duplication and fusion of short sPCP genes produced long sPCP genes. All short and long sPCP genes characterized to date, including those from free living species and Symbiodinium sp. 203 (clade C/type C2) are intronless. However, we observed that long sPCP genes from two Caribbean Symbiodinium clade B isolates each contained two introns. To test the hypothesis that introns were gained during radiation of clade B, we compared sPCP genomic and cDNA sequences from 13 additional distinct Caribbean and Pacific Symbiodinium clade A, B, and F isolates. Long sPCP genes from all clade B/B1 and B/B19 descendants contain orthologs of both introns. Short sPCP genes from S. pilosum (A/A2) and S. muscatinei (B/B4) plus long sPCP genes from S. microadriaticum (A/A1) and S. kawagutii (F/F1) are intronless. Short sPCP genes of S. microadriaticum have a third unique intron. Symbiodinium clade B long sPCP sequences are useful for assessing divergence among B1 and B19 descendants. Phylogenetic analyses of coding sequences from four dinoflagellate orders indicate that introns were gained independently during radiation of Symbiodinium clades A and B. Long sPCP introns were present in the most recent common ancestor of Symbiodinium clade B core types B1 and B19, which apparently diverged sometime during the Miocene. The clade A short sPCP intron was either gained by S. microadriaticum or possibly by the ancestor of Symbiodinium types A/A1, A3, A4 and A5. The timing of short sPCP intron gain in Symbiodinium clade A is less certain. But, all sPCP introns were gained after fusion of ancestral short sPCP genes, which we confirm as occurring once in dinoflagellate evolution.

The Unique Photophysical Properties of the Peridinin-Chlorophyll-a-Protein

Peridinin-Chlorophyll-a-Proteins (PCPs) are water-soluble light harvesting complexes from dinoflagellates. They have unique light-harvesting and energy transfer properties which have been studied in details in the last 15 years. This review aims to give an overview on all the main aspects of PCPs photophysics, with an emphasis on some aspects which have not been reviewed in details so far, such as vibrational spectroscopy studies, theoretical calculations, and magnetic resonance studies. A paragraph on the present development of PCPs towards technological applications is also included.

Quantitative proteomic analysis reveals evolutionary divergence and species-specific peptides in the Alexandrium tamarense complex (Dinophyceae)

The Alexandrium tamarense/catenella/fundyense complex is the major causative agent responsible for harmful algal blooms and paralytic shellfish poisoning around the world. However, taxonomy of the A. tamarense complex is contentious and the evolutionary relationships within the complex are unclear. This study compared protein profiles of the A. tamarense complex collected from different geographic regions using the two dimensional fluorescence difference gel electrophoresis (2-D DIGE) approach, and identified species-specific peptides using MALDI-TOF/TOF mass spectrometry. The results showed that three Alexandrium morphotypes presented significantly different protein expression patterns with about 30-40% shared proteins. However, ecotypes from different geographic regions within a species exhibited the same expression patterns, although a few proteins were altered in abundance. Several proteins, i.e. ribulose-1,5-bisphosphate carboxylase oxygenase form II, plastid protein NAP50, methionine S-adenosyltransferase, and peridinin-chlorophyll a-binding protein, were identified and presented different shift patterns in isoelectric point and/or molecular weight in the 2-D DIGE gels, indicating that amino acid mutation and/or posttranslational modification of these proteins had occurred. The species-specific peptide mass fingerprint and amino acid sequence of ribulose-1,5-bisphosphate carboxylase oxygenase were characterized in the A. tamarense complex, and amino acid substitution occurred among them. This study indicated that evolutionary divergence had occurred at the proteomic level in the A. tamarense complex, and that the species-specific peptides could be used as potential biomarkers to distinguish the three morphotypes. Scientific question: The Alexandrium tamarense/catenella/fundyense complex is the major causative agent responsible for harmful algal blooms and paralytic shellfish poisoning around the world. However, taxonomy of the A. tamarense complex is contentious and the evolutionary relationships within the complex are unclear, which has seriously impeded our understanding of Alexandrium-causing HABs and, consequently, the monitoring, mitigation and prevention. Technical significance: This study, for the first time, compared the global protein expression patterns of eight ecotypes from the A. tamarense complex and identified species-specific peptides using a quantitative proteomic approach combining 2-D DIGE and MALDI-TOF/TOF MS. This study demonstrated that the evolutionary divergence had occurred in the A. tamarense complex at the proteomic level, and the complex should be classified into three species, i.e. A. tamarense, A. catenella, and A. fundyense. Moreover, the species-specific peptide mass fingerprints could be used as potential biomarkers to distinguish the three morphotypes.

Characterization of the peridinin–chlorophyll a-protein complex in the dinoflagellate Symbiodinium

The water-soluble peridinin–chlorophyll a-proteins (PCPs) are one of the major light harvesting complexes in photosynthetic dinoflagellates. PCP contains the carotenoid peridinin as its primary pigment. In this study, we identified and characterized the PCP protein and the PCP gene organization in Symbiodinium sp. CS-156. The protein molecular mass is 32.7kDa, revealing that the PCP is of the monomeric form. The intronless PCP genes are organized in tandem arrays. The PCP gene cassette is composed of 1095-bp coding regions and spacers in between. Despite the heterogeneity of PCP gene tandem repeats, we identified a single form of PCP, the sequence of which exactly matches the deduced sequence of PCP gene clone 7 (JQ395030) by LC–MS/MS analysis of tryptic digested PCP, revealing the mature PCP apoprotein is 312 amino acids in length. Pigment analysis showed a peridinin-to-Chl a ratio of 4. The peridinin-to-Chl a Qy energy transfer efficiency is 95% in this complex.

Structure and function of native and refolded peridinin-chlorophyll-proteins from dinoflagellates

Peridinin-chlorophyll a-proteins are a class of light-harvesting proteins only found in photosynthetic dinoflagellates. Due to their exceptional stability they are an excellent model system to study carotenoid to chlorophyll energy transfer. We were able to solve structures of these complexes at near atomic resolution, allowing the detailed discussion of pigment–pigment and pigment–protein interactions. Using a refolding system, we also determined structures of complexes with mutated apoproteins and modified pigment compositions. Here we summarize the current understanding of PCP structures, with an emphasis on how the basic dimeric structure may be modified in the oligomeric state of these complexes.

Femtosecond Time-Resolved Absorption Spectroscopy of Main-Form and High-Salt Peridinin−Chlorophylla−Proteins at Low Temperatures

Steady-state and femtosecond time-resolved optical methods have been used to compare the spectroscopic features and energy transfer dynamics of two systematically different light-harvesting complexes from the dinoflagellate Amphidinium carterae: main-form (MFPCP) and high-salt (HSPCP) peridinin-chlorophyll a-proteins. Pigment analysis and X-ray diffraction structure determinations [Hofmann, E., Wrench, P. M., Sharples, F. P., Hiller, R. G., Welte, W., Diederichs, K. (1996) Science 272, 1788-1791; T. Schulte, F. P. Sharples, R. G. Hiller, and E. Hofmann, unpublished results] have revealed the composition and geometric arrangements of the protein-bound chromophores. The MFPCP contains eight peridinins and two chlorophyll (Chl) a, whereas the HSPCP has six peridinins and two Chl a, but both have very similar pigment orientations. Analysis of the absorption spectra has shown that the peridinins and Chls absorb at different wavelengths in the two complexes. Also, in the HSPCP complex, the Qy transitions of the Chls are split into two well-resolved bands. Quantum computations by modified neglect of differential overlap with partial single and double configuration interaction (MNDO-PSDCI) methods have revealed that charged amino acid residues within 8 A of the pigment molecules are responsible for the observed spectral shifts. Femtosecond time-resolved optical spectroscopic kinetic data from both complexes show ultrafast (<130 fs) and slower (approximately 2 ps) pathways for energy transfer from the peridinin excited singlet states to Chl. The Chl-to-Chl energy transfer rate constant for both complexes was measured and is discussed in terms of the Förster mechanism. It was found that, upon direct Chl excitation, the Chl-to-Chl energy transfer rate constant for MFPCP was a factor of 4.2 larger than for HSPCP. It is suggested that this difference arises from a combination of factors including distance between Chls, spectral overlap, and the presence of two additional peridinins in MFPCP that act as polarizable units enhancing the rate of Chl-to-Chl energy transfer. The study has revealed specific pigment-protein interactions that control the spectroscopic features and energy transfer dynamics of these light-harvesting complexes.

The 15-kDa forms of the apo-peridinin-chlorophyll a protein (PCP) in dinoflagellates show high identity with the apo-32 kDa PCP forms, and have similar N-terminal leaders and gene arrangements

Full-length genomic sequences encoding apo peridinin-chlorophyll a proteins (PCPs) from Heterocapsa pygmaea have been obtained by PCR. Two of the derived mature proteins of 150 residues have molecular masses of 15,795 and 15,780, respectively. Contrary to an earlier report, these show a high degree of identity (approximately 70%) over the whole of both domains to the mature 32-kDa PCP forms. The two genes lack introns, are arranged in tandem and separated by 526 bp. A putative N-terminal extension with three domains characteristic of a signal sequence, a chloroplast-targeting sequence and a thylakoid lumen-directing sequence, is present. Modelling of the Heterocapsa PCP amino acid sequence on to the high-resolution structure available for Amphidinium PCP shows that the main differences between two forms are in trimer contact regions.

Light-Regulated Transcription of Genes Encoding Peridinin Chlorophyll a Proteins and the Major Intrinsic Light-Harvesting Complex Proteins in the DinoflagellateAmphidinium carterae Hulburt (Dinophycae)1

In the dinoflagellate Amphidinium carterae, photoadaptation involves changes in the transcription of genes encoding both of the major classes of light-harvesting proteins, the peridinin chlorophyll a proteins (PCPs) and the major a/c-containing intrinsic light-harvesting proteins (LHCs). PCP and LHC transcript levels were increased up to 86- and 6-fold higher, respectively, under low-light conditions relative to cells grown at high illumination. These increases in transcript abundance were accompanied by decreases in the extent of methylation of CpG and CpNpG motifs within or near PCP- and LHC-coding regions. Cytosine methylation levels in A. carterae are therefore nonstatic and may vary with environmental conditions in a manner suggestive of involvement in the regulation of gene expression. However, chemically induced undermethylation was insufficient in activating transcription, because treatment with two methylation inhibitors had no effect on PCP mRNA or protein levels. Regulation of gene activity through changes in DNA methylation has traditionally been assumed to be restricted to higher eukaryotes (deuterostomes and green plants); however, the atypically large genomes of dinoflagellates may have generated the requirement for systems of this type in a relatively "primitive" organism. Dinoflagellates may therefore provide a unique perspective on the evolution of eukaryotic DNA-methylation systems.

Structure and organization of the peridinin-chlorophyll a-binding protein gene in Gonyaulax polyedra.

We have identified a major 32-kDa protein in the dinoflagellate Gonyaulax polyedra as a peridinin-chlorophyll a-binding protein (PCP), based on micro-sequence data and immunological cross-reaction with antibodies raised against PCP from another dinoflagellate species. A cDNA for this protein, identified by a PCR-based cloning strategy, encoded all 68 of the amino acids microsequenced, thus confirming the identity of the clone. The PCP gene is highly expressed at both the mRNA and protein levels, and only PCP transcripts corresponding in size to the cDNA sequence were detected. Slot blot analyses show that there are roughly 5000 copies of the PCP gene in Gonyaulax, making this gene one of the most highly repeated protein-coding genes ever reported, yet the sequence of the different gene copies in the genome appears extraordinarily well conserved as judged by Southern blot analyses. The gene, as indicated by Southern blot and PCR data, is suggested to be present in 5000 intronless copies arranged head to tail in the genome, separated by conserved 1-kb spacers. Based on the conserved sequence of the spacer region, its presence next to each of the PCP coding sequences, and the uniform size of the PCP transcript, we propose that this region represents a dinoflagellate transcriptional promoter. This putative promoter region contains none of the sequence elements for DNA-binding proteins involved in transcriptional initiation reported in other organisms.

Two distinct forms of the peridinin-chlorophyll a-protein from Amphidinium carterae

Peridinin-chlorophyll a-proteins (PCPs) have been purified by combination of ammonium sulphate precipitation and cation exchange chromatography. The amino acid sequences of several of the most abundant forms have been deduced by direct protein sequencing and from DNA and indicate a highly conserved multi-gene family. At least two of the PCP genes are tandemly arranged. A novel form of the protein was also obtained in low yield with fewer peridinins (six vs eight) per chlorophyll a and with a different molecular mass (34 kDa vs 32 kDa) of its apoprotein. It had only 31% sequence identity with any of the more abundant PCP forms but retained a two-domain structure.

Nucleotide sequence of a cDNA clone encoding the precursor of the peridinin-chlorophyll a-binding protein from the dinoflagellate Symbiodinium sp.

mRNA from the dinoflagellate Symbiodinium sp. isolated from the staghorn coral Acropora formosa was used for the construction of cDNA libraries. A cDNA clone was identified which encoded the precursor of peridinin-chlorophyll a-binding protein (PCP), including a 52 amino acid transit peptide and the 313 amino acid mature protein. The deduced amino acid sequence clearly contains an internal duplication, implying that amongst dinoflagellates the M(r) 35,000 form of PCP has arisen by duplication and fusion of genes encoding the M(r) 15,000 form. This is the first reported sequence of a dinoflagellate light-harvesting protein. The anatomy of the mature protein and the transit peptide are discussed.

Tetrameric native structure of the peridinin-chlorophyll a-binding protein from Symbiodinium Sp.

Summary Electron microscopy of a single isoform of the peridinin-chlorophyll a-binding protein from Symbiodinium sp. indicates that the native structure is a tetrahedron-like assembly of four subunits. The subunits are elongated and have a somewhat bent appearance. Based on the EM observations, a working model is proposed that has two orthogonally-arranged dimers in contact via their concave surfaces.

Photoadaptation of photosynthesis in Gonyaulax polyedra

Gonyaulax polyedra Stein exhibited a combination of photoadaptive strategies of photosynthesis when only a single environmental variable, the light intensity during growth, was altered. Which of several biochemical/physiological adjustments to the light environment were employed depended on the level of growth irradiance. The photoadaptive strategies employed over any small range of light levels appeared to be those best suited for optimizing photosynthetic performance and not photosynthetic capacity. (Photosynthetic performance, Pi, is defined as the rate of photosynthesis occurring at the level of growth irradiance.) Among all photosynthetic parameters examined, only photosynthetic performance showed a consistent correspondence to growth rates of G. polyedra. Above 3500 to 4000 μW cm-2, where photosynthetic performance was equal to photosynthetic capacity, cells were not considered light-limited in either photosynthesis or growth. At these higher light levels, photosynthetic perfomance, cell volume, growth rates and respiration rates remained maximal; photosynthetic pigment content varied only slightly, while the photosynthetic capacity of the cells declined. At intermediate light levels (3000 to 1500 μW cm-2), photosynthesis, not growth, was light-limited, and photoadaptive strategies were induced which enhance absorption capabilities and energy transfer efficiencies of chlorophyll a to the reaction centers of G. polyedra. Photosynthetic capacity remained constant at about 280 μmol O2 cm-3 h-1, while photosynthetic performance ranged from 100 to 130 μmol O2 cm-3 h-1. Major increases in photosynthetic pigments, especially peridinin-chlorophyll a-proteins and an unidentified chlorophyll c component, accompanied photoadaptation to low irradiances. Maximal growth rates of 0.3 divisions day-1 were maintained, as were respiration rates of about-80 μmol O2 cm-3 h-1 and cell volumes of about 5.4×10-8 cm-3 cell-1. Below about 1250 μW cm-2, photosynthesis in G. polyedra was so light-limited that photosynthetic performance was unable to support maximal growth rates. Under these conditions, G. polyedra displayed photostress responses rather than photoadaptive strategies. Photostress was manifested as reduced cell volumes, slower growth, and drastic reductions in pigmentation, photosynthetic capacity, and rates of dark respiration.

Purification and characterization of peridinin-chlorophyll a-proteins from the marine dinoflagellates Glenodinium sp. and Gonyaulax polyedra

A peridinin-chlorophyll a-protein complex (PCP) was obtained in large quantity from the marine dinoflagellates, Glenodinium sp. and Gonyaulax polyedra. The chromoproteins have similar molecular weights, 35,500 for Glenodinium sp. and 34,500 for G. polyedra. The proteins from the PCP complex of Glenodinium sp. dissociated from the chromophore on treatment with 1% sodium dodecyl sulfate (SDS) at room temperature. The protein component was a single subunit with a molecular weight of 15,500. Proteins from the PCP complex of G. polyedra were composed of a single polypeptide with a molecular weight of about 32,000. Two peridinin-chlorophyll a-proteins from Glenodinium sp. accounted for 70% of the PCP complex and had isoelectric points of 7.4 and 7.3. The PCP complex from G. polyedra was dominated by a single chromoprotein with an isoelectric point of 7.2 Chromophore analysis indicated the presence of only peridinin and chlorophyll a in a molar ratio approaching 4:1. Other pigments characteristically found in dinoflagellates were absent. Fluorescence excitation spectra of purified PCP indicated an efficient energy transfer from peridinin to chlorophyll a, an observation that lends support to the reported role of peridinin as an accessory pigment in photosynthetic oxygen evolution. In several other brown colored dinoflagellates examined, PCP representtd less than 20% of the total peridinin. However, no PCP could be isolated from cultures of Amphidinium carterae (PY-1). This study provides further evidence that PCP is a normal component of most peridinin-containing dinoflagellates, and functions as a light-harvesting component of the dinoflagellate chloroplast. No fucoxanthin-containing analog of PCP was detected in the chrysophyte, Cricosphera carterae and the dinoflagellate Glenodinium foliaceum.