The structural basis for light harvesting in organisms producing phycobiliproteins.

Cyanobacteria, red algae, and cryptophytes produce two classes of proteins for light-harvesting: water-soluble phycobiliproteins and membrane-intrinsic proteins that bind chlorophylls and carotenoids. In cyanobacteria, red algae, and glaucophytes, phycobilisomes (PBS) are complexes of brightly colored phycobiliproteins and linker (assembly) proteins. To date, six structural classes of phycobilisomes have been described: hemiellipsoidal, block-shaped, hemidiscoidal, bundle-shaped, paddle-shaped, and far-red-light bicylindrical. Two additional antenna complexes containing single types of phycobiliproteins have also been described. Since 2017, structures have been reported for examples of all of these complexes except bundle-shaped phycobilisomes by cryogenic electron microscopy. Phycobilisomes range in size from about 4.6 to 18 MDa and can include ∼900 polypeptides and bind >2000 chromophores. Cyanobacteria additionally produce membrane-associated proteins of the PsbC/CP43 superfamily of Chl a/b/d-binding proteins, including the iron-stress protein IsiA and other paralogous chlorophyll-binding proteins that can form antenna complexes with Photosystem I and/or Photosystem II. Red and cryptophyte algae also produce chlorophyll-binding proteins associated with Photosystem I but which belong to the chlorophyll a/b-binding (CAB) protein superfamily and which are unrelated to the chlorophyll-binding proteins (CBP) of cyanobacteria. This review describes recent progress in structure determination for phycobilisomes and the chlorophyll proteins of cyanobacteria, red algae, and cryptophytan algae.

Extremophilic red algae as models for understanding adaptation to hostile environments and the evolution of eukaryotic life on the early earth.

Extremophiles have always garnered great interest because of their exotic lifestyles and ability to thrive at the physical limits of life. In hot springs environments, the Cyanidiophyceae red algae are the only photosynthetic eukaryotes able to live under extremely low pH (0-5) and relatively high temperature (35ºC to 63ºC). These extremophiles live as biofilms in the springs, inhabit acid soils near the hot springs, and form endolithic populations in the surrounding rocks. Cyanidiophyceae represent a remarkable source of knowledge about the evolution of extremophilic lifestyles and their genomes encode specialized enzymes that have applied uses. Here we review the evolutionary origin, taxonomy, genome biology, industrial applications, and use of Cyanidiophyceae as genetic models. Currently, Cyanidiophyceae comprise a single order (Cyanidiales), three families, four genera, and nine species, including the well-known Cyanidioschyzon merolae and Galdieria sulphuraria. These algae have small, gene-rich genomes that are analogous to those of prokaryotes they live and compete with. There are few spliceosomal introns and evidence exists for horizontal gene transfer as a driver of local adaptation to gain access to external fixed carbon and to extrude toxic metals. Cyanidiophyceae offer a variety of commercial opportunities such as phytoremediation to detoxify contaminated soils or waters and exploitation of their mixotrophic lifestyles to support the efficient production of bioproducts such as phycocyanin and floridosides. In terms of exobiology, Cyanidiophyceae are an ideal model system for understanding the evolutionary effects of foreign gene acquisition and the interactions between different organisms inhabiting the same harsh environment on the early Earth. Finally, we describe ongoing research with C. merolae genetics and summarize the unique insights they offer to the understanding of algal biology and evolution.

Development of a rapamycin-inducible protein-knockdown system in the unicellular red alga Cyanidioschyzon merolae.

An inducible protein-knockdown system is highly effective for investigating the functions of proteins and mechanisms essential for the survival and growth of organisms. However, this technique is not available in photosynthetic eukaryotes. The unicellular red alga Cyanidioschyzon merolae possesses a very simple cellular and genomic architecture and is genetically tractable but lacks RNA interference machinery. In this study, we developed a protein-knockdown system in this alga. The constitutive system utilizes the destabilizing activity of the FRB domain of human target of rapamycin (TOR) kinase or its derivatives to knock down target proteins. In the inducible system, rapamycin treatment induces the heterodimerization of the human FKBP12-rapamycin binding (FRB) domain fused to the target proteins with the human FK506-binding protein 12 (FKBP) fused to S-phase kinase associated protein 1 (SKP1) or Cullin 1 (CUL1), subunits of the SCF E3 ubiquitin ligase. This results in the rapid degradation of the target proteins through the ubiquitin-proteasome pathway. With this system, we successfully degraded endogenous essential proteins such as the chloroplast division protein Dynamin related protein 5B (DRP5B) and E2 transcription factor (E2F), a regulator of the G1/S transition, within 2-3 hours after rapamycin administration, enabling the assessment of resulting phenotypes. This rapamycin-inducible protein-knockdown system contributes to the functional analysis of genes whose disruption leads to lethality.

A novel class of xylanases specifically degrade marine red algal ß1,3/1,4-mixed-linkage xylan.

Xylans are polysaccharides composed of xylose and include ß1,4-xylan, ß1,3-xylan, and ß1,3/1,4-mixed-linkage xylan (MLX). MLX is widely present in marine red algae and constitutes a significant organic carbon in the ocean. Xylanases are hydrolase enzymes that play an important role in xylan degradation. While a variety of ß1,4-xylanases and ß1,3-xylanases involved in the degradation of ß1,4-xylan and ß1,3-xylan have been reported, no specific enzyme has yet been identified that degrades MLX. Herein, we report the characterization of a new MLX-specific xylanase from the marine bacterium Polaribacter sp. Q13 which utilizes MLX for growth. The bacterium secretes xylanases to degrade MLX, among which is Xyn26A, an MLX-specific xylanase that shows low sequence similarities (<27%) to ß1,3-xylanases in the glycoside hydrolase family 26 (GH26). We show that Xyn26A attacks MLX precisely at ß1,4-linkages, following a ß1,3-linkage toward the reducing end. We confirm that Xyn26A and its homologs have the same specificity and mode of action on MLX, and thus represent a new xylanase group which we term as MLXases. We further solved the structure of a representative MLXase, AlXyn26A. Structural and biochemical analyses revealed that the specificity of MLXases depends critically on a precisely positioned ß1,3-linkage at the -2/-1 subsite. Compared to the GH26 ß1,3-xylanases, we found MLXases have evolved a tunnel-shaped cavity that is fine-tuned to specifically recognize and hydrolyze MLX. Overall, this study offers a foremost insight into MLXases, shedding light on the biochemical mechanism of bacterial degradation of MLX.

The catabolic specialization of the marine bacterium Polaribacter sp. Q13 to red algal ß1,3/1,4-mixed-linkage xylan.

Catabolism of algal polysaccharides by marine bacteria is a significant process of marine carbon cycling. ß1,3/1,4-Mixed-linkage xylan (MLX) is a class of xylan in the ocean, widely present in the cell walls of red algae. However, the catabolic mechanism of MLX by marine bacteria remains elusive. Recently, we found that a marine Bacteroidetes strain, Polaribacter sp. Q13, is a specialist in degrading MLX, which secretes a novel MLX-specific xylanase. Here, the catabolic specialization of strain Q13 to MLX was studied by multiomics and biochemical analyses. Strain Q13 catabolizes MLX with a canonical starch utilization system (Sus), which is encoded by a single xylan utilization locus, XUL-Q13. In this system, the cell surface glycan-binding protein SGBP-B captures MLX specifically, contributing to the catabolic specificity. The xylanolytic enzyme system of strain Q13 is unique, and the enzymatic cascade dedicates the stepwise hydrolysis of the ß1,3- and ß1,4-linkages in MLX in the extracellular, periplasmic, and cytoplasmic spaces. Bioinformatics analysis and growth observation suggest that other marine Bacteroidetes strains harboring homologous MLX utilization loci also preferentially utilize MLX. These results reveal the catabolic specialization of MLX degradation by marine Bacteroidetes, leading to a better understanding of the degradation and recycling of MLX driven by marine bacteria.IMPORTANCERed algae contribute substantially to the primary production in marine ecosystems. The catabolism of red algal polysaccharides by marine bacteria is important for marine carbon cycling. Mixed-linkage ß1,3/1,4-xylan (MLX, distinct from hetero-ß1,4-xylans from terrestrial plants) is an abundant red algal polysaccharide, whose mechanism of catabolism by marine bacteria, however, remains largely unknown. This study reveals the catabolism of MLX by marine Bacteroidetes, promoting our understanding of the degradation and utilization of algal polysaccharides by marine bacteria. This study also sets a foundation for the biomass conversion of MLX.

Roseibium algicola sp. nov. and Roseibium porphyridii sp. nov., isolated from marine red algae.

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6T and KMA01T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6T exhibited flagellar motility, while those of strain KMA01T were non-motile. Strain RMAR6-6T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01T grew optimally at 30-35 °C, pH 7.0-8.0 and 2.0-5.0% NaCl. Both strains shared common major respiratory isoprenoid quinone (ubiquinone-10), cellular fatty acids (C18 : 0, C18: 1 ω7c 11-methyl, C20 : 1 ω7c and summed feature 8) and polar lipids (phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and sulphoquinovosyldiacylglycerol). The genomic DNA G+C contents were 59.0 and 55.0 mol% for strains RMAR6-6T and KMA01T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6T and KMA01T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6T and KMA01T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614T and Roseibium album CECT 5094T, respectively. The ANI and dDDH values between strain RMAR6-6T and R. aggregatum IAM 12614T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01T and R. album CECT 5094T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6T and KMA01T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6T=KACC 22482T=JCM 34977T) and R. porphyridii sp. nov. (KMA01T=KACC 22479T=JCM 34597T) are proposed, respectively.

Characterization of the organellar genomes of Mazzaella laminarioides and Mazzaella membranacea (Gigartinaceae, Rhodophyta).

Mazzaella, a genus with no genomic resources available, has extensive distribution in the cold waters of the Pacific, where they represent ecologically and economically important species. In this study, we aimed to sequence, assemble, and annotate the complete mitochondrial and chloroplast genomes from two Mazzaella spp. and characterize the intraspecific variation among them. We report for the first time seven whole organellar genomes (mitochondria: OR915856, OR947465, OR947466, OR947467, OR947468, OR947469, OR947470; chloroplast: OR881974, OR909680, OR909681, OR909682, OR909683, OR909684, OR909685) obtained through high-throughput sequencing for six M. laminarioides sampled from three Chilean regions and one M. membranacea. Sequenced Mazzaella mitogenomes have identical gene number, gene order, and genome structure. The same results were observed for assembled plastomes. A total of 52 genes were identified in mitogenomes, and a total of 235 genes were identified in plastomes. Although the M. membranacea plastome included a full-length pbsA gene, in all M. laminarioides samples, the pbsA gene was split in three open reading frames (ORFs). Within M. laminarioides, we observed important plastome lineage-specific variations, such as the pseudogenization of the two hypothetical protein-coding genes, ycf23 and ycf45. Nonsense mutations in the ycf23 and ycf45 genes were only detected in the northern lineage. These results are consistent with phylogenetic reconstructions and divergence time estimation using concatenated coding sequences that not only support the monophyly of M. laminarioides but also underscore that the three M. laminarioides lineages are in an advanced stage of divergence. These new results open the question of the existence of still undisclosed species in M. laminarioides.

An investigation on antimicrobial and anticancer competence of macro red algae under in-vitro condition.

The purpose of this study was to look into the proximate parameters (moisture, ash, total fat, protein, and total carbohydrate), mineral composition (Fe, Cu, Mg, and Zn), antimicrobial as well as cytotoxic (anticancer) properties of extracts from the marine red macro algae Gracilaria corticata, Chondrus ocellatus, and Posphyra perforata against a few prevalent microbial pathogens (Salmonella typhi, Streptococcus pneumoniae, Corynebacterium diphtheriae, Clostridium tetani, and Treponema pallidum as well as fungal pathogens such as Candida albicans, Aspergillus niger, and Cryptococcus neoformans) and two cancerous cell lines (HeLa and MCF7). The dry biomass of these red algae biomass contains considerable valuable proximate parameters and minerals. The diffusion technique on agar wells was used to evaluate the antimicrobial properties of these test red algae methanol and hexane extract; MTT assay was used to evaluate the cytotoxic effects of the methanol and hexane extracts on each cancer cell line. The methanol extracts demonstrated significant antimicrobial activity against most of the tested pathogenic organisms. Mortality of cells was effectively caused by methanol extract and it followed by hexane extract at increased dosage 10 mg mL-1. The MTT assay revealed that the methanol extract of the red algae was considerably cytotoxic to HeLa and MCF7 cells, accompanied by the hexane extract in a dose-dependent manner. These findings suggest that the methanol extract of these red algae may contain bioactive compounds with antimicrobial and anticancer properties, which could be studied for future use in the discovery of new drugs from marine ecosystems.

Extraction and antioxidant capacity of mycosporine-like amino acids from red algae in Japan.

Mycosporine-like amino acids (MAAs) are the natural UV-absorbing compounds with antioxidant activity found in microalgae and macroalgae. We collected red algae Asparagopsis taxiformis, Meristotheca japonica, and Polysiphonia senticulosa from Nagasaki, where UV radiation is more intense than in Hokkaido, and investigated the effect of UV radiation on MAA content. It was suggested that A. taxiformis and M. japonica contained shinorine and palythine, while UV-absorbing compound in P. senticulosa could not be identified. The amounts of these MAAs were lower compared to those from Hokkaido. Despite an increase in UV radiation in both regions from February to April, MAA contents of red algae from Nagasaki slightly decreased while those from Hokkaido significantly decreased. This difference was suggested the amount of inorganic nitrogen in the ocean. Antioxidant activity of MAAs increased under alkaline conditions. The extract containing MAAs from P. senticulosa showed the highest antioxidant activity among 4 red algae.

Functional Characterization of the First Bona Fide Phytoene Synthase in Red Algae from Pyropia yezoensis.

The formation of phytoene by condensing two geranylgeranyl diphosphate molecules catalyzed by phytoene synthase (PSY) is the first committed and rate-limiting step in carotenoid biosynthesis, which has been extensively investigated in bacteria, land plants and microalgae. However, this step in macroalgae remains unknown. In the present study, a gene encoding putative phytoene synthase was cloned from the economic red alga Pyropia yezoensis-a species that has long been used in food and pharmaceuticals. The conservative motifs/domains and the tertiary structure predicted using bioinformatic tools suggested that the cloned PyPSY should encode a phytoene synthase; this was empirically confirmed by pigment complementation in E. coli. This phytoene synthase was encoded by a single copy gene, whose expression was presumably regulated by many factors. The phylogenetic relationship of PSYs from different organisms suggested that red algae are probably the progeny of primary endosymbiosis and plastid donors of secondary endosymbiosis.

Halogenated Cyclic Monoterpenoids with Anti-Biofouling Activity from the Okinawan Red Marine Algae Portieria Hornemannii.

The red algal genus Portieria is a prolific producer of halogenated monoterpenoids. In this study, we isolated and characterised monoterpenoids from the Okinawan red algae Portieria hornemannii. A new polyhalogenated cyclic monoterpenoid, 2(R)-chloro-1,6(S)-dibromo-3(8)(Z)-ochtoden-4(R)-ol (1), along with three known monoterpenoids, (2R,3(8)E,4S,6R)-6-bromo-2-chloro-1,4-oxido-3(8)-ochtodene (2), 1-bromo-2-chloroochtoda-3(8),5-dien-4-one (3), and 2-chloro-1-hydroxyochtoda-3(8),5-dien-4-one (4) were isolated from the methanol extract of three populations of P. hornemannii. These compounds were characterised using a combination of spectroscopic methods and chemical synthesis, and the absolute stereochemistry of compounds 1 and 2 was determined. In addition, all isolated compounds were screened for their anti-biofouling activity against the mussel Mytilus galloprovincialis, and 1 exhibited strong activity. Therefore, halogenated monoterpenoids have the potential to be used as natural anti-biofouling drugs.

The Extract of Gloiopeltis tenax Enhances Myogenesis and Alleviates Dexamethasone-Induced Muscle Atrophy.

The decline in the function and mass of skeletal muscle during aging or other pathological conditions increases the incidence of aging-related secondary diseases, ultimately contributing to a decreased lifespan and quality of life. Much effort has been made to surmise the molecular mechanisms underlying muscle atrophy and develop tools for improving muscle function. Enhancing mitochondrial function is considered critical for increasing muscle function and health. This study is aimed at evaluating the effect of an aqueous extract of Gloiopeltis tenax (GTAE) on myogenesis and muscle atrophy caused by dexamethasone (DEX). The GTAE promoted myogenic differentiation, accompanied by an increase in peroxisome proliferator-activated receptor γ coactivator α (PGC-1α) expression and mitochondrial content in myoblast cell culture. In addition, the GTAE alleviated the DEX-mediated myotube atrophy that is attributable to the Akt-mediated inhibition of the Atrogin/MuRF1 pathway. Furthermore, an in vivo study using a DEX-induced muscle atrophy mouse model demonstrated the efficacy of GTAE in protecting muscles from atrophy and enhancing mitochondrial biogenesis and function, even under conditions of atrophy. Taken together, this study suggests that the GTAE shows propitious potential as a nutraceutical for enhancing muscle function and preventing muscle wasting.

Specificity of a ß-porphyranase produced by the carrageenophyte red alga Chondrus crispus and implications of this unexpected activity on red algal biology.

The carrageenophyte red alga Chondrus crispus produces three family 16 glycoside hydrolases (CcGH16-1, CcGH16-2, and CcGH16-3). Phylogenetically, the red algal GH16 members are closely related to bacterial GH16 homologs from subfamilies 13 and 14, which have characterized marine bacterial ß-carrageenase and ß-porphyranase activities, respectively, yet the functions of these CcGH16 hydrolases have not been determined. Here, we first confirmed the gene locus of the ccgh16-3 gene in the alga to facilitate further investigation. Next, our biochemical characterization of CcGH16-3 revealed an unexpected ß-porphyranase activity, since porphyran is not a known component of the C. crispus extracellular matrix. Kinetic characterization was undertaken on natural porphyran substrate with an experimentally determined molecular weight. We found CcGH16-3 has a pH optimum between 7.5 and 8.0; however, it exhibits reasonably stable activity over a large pH range (pH 7.0-9.0). CcGH16-3 has a KM of 4.0 ± 0.8 µM, a kcat of 79.9 ± 6.9 s-1, and a kcat/KM of 20.1 ± 1.7 µM-1 s-1. We structurally examined fine enzymatic specificity by performing a subsite dissection. CcGH16-3 has a strict requirement for D-galactose and L-galactose-6-sulfate in its -1 and +1 subsites, respectively, whereas the outer subsites are less restrictive. CcGH16-3 is one of a handful of algal enzymes characterized with a specificity for a polysaccharide unknown to be found in their own extracellular matrix. This ß-porphyranase activity in a carrageenophyte red alga may provide defense against red algal pathogens or provide a competitive advantage in niche colonization.

Red macroalgae in the genomic era.

Rhodophyta (or red algae) are a diverse and species-rich group that forms one of three major lineages in the Archaeplastida, a eukaryotic supergroup whose plastids arose from a single primary endosymbiosis. Red algae are united by several features, such as relatively small intron-poor genomes and a lack of cytoskeletal structures associated with motility like flagella and centrioles, as well as a highly efficient photosynthetic capacity. Multicellular red algae (or macroalgae) are one of the earliest diverging eukaryotic lineages to have evolved complex multicellularity, yet despite their ecological, evolutionary, and commercial importance, they have remained a largely understudied group of organisms. Considering the increasing availability of red algal genome sequences, we present a broad overview of fundamental aspects of red macroalgal biology and posit on how this is expected to accelerate research in many domains of red algal biology in the coming years.

Biochemical and spectroscopic characterization of PSI-LHCI from the red alga Cyanidium caldarium.

Light-harvesting complexes (LHCs) have been diversified in oxygenic photosynthetic organisms, and play an essential role in capturing light energy which is transferred to two types of photosystem cores to promote charge-separation reactions. Red algae are one of the groups of photosynthetic eukaryotes, and their chlorophyll (Chl) a-binding LHCs are specifically associated with photosystem I (PSI). In this study, we purified three types of preparations, PSI-LHCI supercomplexes, PSI cores, and isolated LHCIs, from the red alga Cyanidium caldarium, and examined their properties. The polypeptide bands of PSI-LHCI showed characteristic PSI and LHCI components without contamination by other proteins. The carotenoid composition of LHCI displayed zeaxanthins, ß-cryptoxanthins, and ß-carotenes. Among the carotenoids, zeaxanthins were enriched in LHCI. On the contrary, both zeaxanthins and ß-cryptoxanthins could not be detected from PSI, suggesting that zeaxanthins and ß-cryptoxanthins are bound to LHCI but not PSI. A Qy peak of Chl a in the absorption spectrum of LHCI was shifted to a shorter wavelength than those in PSI and PSI-LHCI. This tendency is in line with the result of fluorescence-emission spectra, in which the emission maxima of PSI-LHCI, PSI, and LHCI appeared at 727, 719, and 677 nm, respectively. Time-resolved fluorescence spectra of LHCI represented no 719 and 727-nm fluorescence bands from picoseconds to nanoseconds. These results indicate that energy levels of Chls around/within LHCIs and within PSI are changed by binding LHCIs to PSI. Based on these findings, we discuss the expression, function, and structure of red algal PSI-LHCI supercomplexes.

Resolving some of the earliest names for Corallina species (Corallinales, Rhodophyta) in the North Pacific by sequencing type specimens and describing the cryptic C. hakodatensis sp. nov. and C. parva sp. nov.

Partial rbcL sequences from type specimens of three of the earliest described Corallina species showed that C. arbuscula (type locality: Unalaska Island, Alaska, USA) and C. pilulifera (type locality: Okhotsk Sea, Russia) are synonymous, with C. pilulifera as the taxonomically accepted name and that C. vancouveriensis (type locality: Botanical Beach, Vancouver Island, Canada) is a distinct species. To identify molecular species limits and clarify descriptions and distributions of C. pilulifera and C. vancouveriensis, we sequenced and analyzed portions of one mitochondrial and two plastid genes from historical and recent collections. The single-gene phylogenetic reconstructions support the recognition of both species as distinct, as well as two additional species, C. hakodatensis sp. nov. and C. parva sp. nov., which are sister to, and often morphologically indistinguishable from C. pilulifera and C. vancouveriensis, respectively. DNA sequence data currently illustrate that C. pilulifera is found in the cold northern Pacific waters from the Okhotsk Sea of Russia to Hokkaido, Japan, eastward across the Aleutian Islands to Knoll Head, Alaska, and as far south as Nanaimo, British Columbia. Corallina vancouveriensis is distributed as far west as Attu Island in the Aleutian Islands to Sitka, Alaska, and southeasterly at numerous sites from British Columbia to the north of Point Conception, California, USA. The cryptic species C. hakodatensis and C. parva occur sympatrically with their sister species but with narrower ranges. The complex phylogenetic relationships shown by the single gene trees recommend Corallina as a model genus to explore coralline algal biogeography, evolution, and patterns of speciation.

A temporal and spatial study of genetic structure in four species of bladed Bangiales (Rhodophyta) from the southeastern Pacific coast of Chile.

The coastline is a heterogeneous and highly dynamic environment influenced by abiotic and biotic variables affecting the temporal stability of genetic diversity and structure of marine organisms. The aim of this study was to determine how much the genetic structure of four species of marine Bangiales vary in time and space. Partial sequences of the cytochrome oxidase I (COI) gene obtained from two Pyropia (Py. sp. CHJ and Py. orbicularis) and two Porphyra (P. mumfordii and P. sp. FIH) species were used to compare the effect of the 40° S/41° S biogeographic break (spatial-regional scale) and the one of the Valdivia River discharges (spatial-local scale) and determine their temporal stability. Four seasonal samplings were taken during 1 year at five sites, one site located in Melinka (Magallanes province) and four sites along the coast of Valdivia (Intermediate area), on both sides of the river mouth. Results showed a strong genetic spatial structure at regional scale (ΦST > 0.4) in Py. sp. CHJ, Py. orbicularis, and P. mumfordii, congruent with the 41° S/42° S biogeographic break. A potential barrier to gene flow, related to the Valdivia River discharge, was detected only in P. mumfordii. In P. sp. FIH, spatial genetic structure was not detected at any scale. The genetic structure of all four species is stable throughout the year. The potential effect of main currents and river discharge in limiting the transport of Bangiales spores are discussed. We propose that both a restricted propagule dispersal and the formation potential for persistent banks of microscopic stages could lead to a temporally stable spatial partitioning of genetic variation in bladed Bangiales.

Antibacterial Activities and Life Cycle Stages of Asparagopsis armata: Implications of the Metabolome and Microbiome.

The red alga Asparagopsis armata is a species with a haplodiplophasic life cycle alternating between morphologically distinct stages. The species is known for its various biological activities linked to the production of halogenated compounds, which are described as having several roles for the algae such as the control of epiphytic bacterial communities. Several studies have reported differences in targeted halogenated compounds (using gas chromatography-mass spectrometry analysis (GC-MS)) and antibacterial activities between the tetrasporophyte and the gametophyte stages. To enlarge this picture, we analysed the metabolome (using liquid chromatography-mass spectrometry (LC-MS)), the antibacterial activity and the bacterial communities associated with several stages of the life cycle of A. armata: gametophytes, tetrasporophytes and female gametophytes with developed cystocarps. Our results revealed that the relative abundance of several halogenated molecules including dibromoacetic acid and some more halogenated molecules fluctuated depending on the different stages of the algae. The antibacterial activity of the tetrasporophyte extract was significantly higher than that of the extracts of the other two stages. Several highly halogenated compounds, which discriminate algal stages, were identified as candidate molecules responsible for the observed variation in antibacterial activity. The tetrasporophyte also harboured a significantly higher specific bacterial diversity, which is associated with a different bacterial community composition than the other two stages. This study provides elements that could help in understanding the processes that take place throughout the life cycle of A. armata with different potential energy investments between the development of reproductive elements, the production of halogenated molecules and the dynamics of bacterial communities.

Development of a Sequential Fractionation-and-Recovery Method for Multiple Anti-Inflammatory Components Contained in the Dried Red Alga Dulse (Palmaria palmata).

A separation process was established to sequentially fractionate and recover three anti-inflammatory components derived from sugars, phycobiliprotein, and chlorophyll from the hot-air-dried thalli of the red alga dulse (Palmaria palmata). The developed process consisted of three steps, without the use of organic solvents. In Step I, the sugars were separated by disrupting the cell wall of the dried thalli with a polysaccharide-degrading enzyme, and a sugar-rich extract (E1) was obtained by precipitating the other components, which were simultaneously eluted by acid precipitation. In Step II, the residue suspension from Step I was digested with thermolysin to obtain phycobiliprotein-derived peptides (PPs), and a PP-rich extract (E2) was obtained by separating the other extracts using acid precipitation. In Step III, solubilized chlorophyll was obtained by heating the residue, which was acid-precipitated, neutralized, and re-dissolved to concentrate the chlorophyll-related components (Chls)-rich extract (E3). These three extracts suppressed inflammatory-cytokine secretion by lipopolysaccharide (LPS)-stimulated macrophages, confirming that the sequential procedure had no negative effects on the activities of any of the extracts. The E1, E2, and E3 were rich in sugars, PPs, and Chls, respectively, indicating that the anti-inflammatory components were effectively fractionated and recovered through the separation protocol.

Group II intron and repeat-rich red algal mitochondrial genomes demonstrate the dynamic recent history of autocatalytic RNAs.

BACKGROUND: Group II introns are mobile genetic elements that can insert at specific target sequences, however, their origins are often challenging to reconstruct because of rapid sequence decay following invasion and spread into different sites. To advance understanding of group II intron spread, we studied the intron-rich mitochondrial genome (mitogenome) in the unicellular red alga, Porphyridium. RESULTS: Analysis of mitogenomes in three closely related species in this genus revealed they were 3-6-fold larger in size (56-132 kbp) than in other red algae, that have genomes of size 21-43 kbp. This discrepancy is explained by two factors, group II intron invasion and expansion of repeated sequences in large intergenic regions. Phylogenetic analysis demonstrates that many mitogenome group II intron families are specific to Porphyridium, whereas others are closely related to sequences in fungi and in the red alga-derived plastids of stramenopiles. Network analysis of intron-encoded proteins (IEPs) shows a clear link between plastid and mitochondrial IEPs in distantly related species, with both groups associated with prokaryotic sequences. CONCLUSION: Our analysis of group II introns in Porphyridium mitogenomes demonstrates the dynamic nature of group II intron evolution, strongly supports the lateral movement of group II introns among diverse eukaryotes, and reveals their ability to proliferate, once integrated in mitochondrial DNA.