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At least 19 recordsLinked to original sources
PubMed2026

Phylogenomics and female reproductive morphology reframe the classification of the Halymeniales (Rhodophyta).

The red algal order Halymeniales (Rhodophyta) exhibits remarkable morphological and taxonomic diversity but its higher-level relationships remain poorly resolved. Here, we present a comprehensive phylogenomic analysis based on newly generated plastid (170 protein-coding genes), mitochondrial (23 genes), and complete nuclear ribosomal cistron sequences from 56 taxa, complemented with an expanded rbcL dataset encompassing 334 sequences. Our results provide a robust phylogenomic framework for the Halymeniales, offering a taxonomic backbone for future systematic studies. The analyses consistently recover six early-diverging lineages (Acrodiscus, Isabbottia, Norrissia, Pachymenia, Zymurgia, and Tsengia) and two strongly supported larger clades (Halymenia s.l. and Grateloupia s.l.). While most small and recently described genera are monophyletic, several traditional genera (e.g., Halymenia, Cryptonemia, Grateloupia) are poly- or paraphyletic, requiring considerable taxonomic revision. At the family level, the data indicate that reinstatement of the Grateloupiaceae sensu Kim et al. (2021) would entail a revised circumscription of the Halymeniaceae and the recognition of at least five small families to accommodate the early-diverging lineages. Although such a revised classification would result in monophyletic families, it is not supported by morpho-anatomical characters. Instead, we propose a more stable two-family system, recognizing a broadly circumscribed Halymeniaceae that is sister to the Tsengiaceae. Female reproductive characters, particularly the structure of carpogonial and auxiliary cell ampullae, support this two-family system and further characterize many genus-level clades, although substantial convergence across lineages exists.

Phylogeny↗
PubMedDate not supplied

Picosecond fluorescence from photosynthetic systems in vivo.

Picosecond time-resolved fluorescence emission from the pigments of intact photosynthetic systems and isolated pigment-protein fractions has been used to probe the mechanism of energy transfer and the organization of the pigments. The fluorescence kinetics of chlorophyll and the phycobilins of the red alga, Porphyridium cruentum, are governed by time-dependent kinetics, but the observed time dependence of the chlorophyll a fluorescence decay from dark-adapted Chlorella pyrenoidosa and spinach sub-chloroplast fractions is still open to conjecture. In contrast to the green plants containing only chlorophyll and carotenoids, Porphyridium shows distinct emission bands for each the pigments in the transfer sequence. The rate of energy transfer in vivo has the empirical form: dS/dt = -1/2S At-1/2, where S is the excited-state population of the donor pigment and A is the overall rate of energy transfer to the acceptor pigment. The kinetic analysis can describe closely the observed fluorescence risetimes and lifetimes of the photosynthetic pigments of Porphyridium. The extremely rapid rates of energy transfer, determined by this treatment, imply that exciton migration within each pigment bed of the phycobilisome is less extensive than in the chlorophyll-antenna systems. Changes in the fluorescence yield and decay kinetics of chlorophyll a and allophycocyanin in vivo can be induced at high excitation intensities by exciton-exciton annihilation.

Chlorophyll↗
PubMed1979

Quantitative X-ray microanalysis of halogen elements in biological specimens.

Standards were prepared for quantitative X-ray microanalysis of the halogen elements Cl, Br and I in sections of resin embedded biological specimens. Halogenated aromatic compounds were dissolved in resin, which subsequently was polymerized. Homogeneity and stability of the standards were determined and found to be satisfactory. A general procedure of calculation of elemental concentrations according to the continuum method is given for the case that the specimen contains appreciable concentrations of one or more rather heavy elements. It is shown that use of approximations may lead to unacceptable errors, even in the concentration ranges occurring in biological specimens. As a practical application, the concentration of bromine in the chloroplasts of the red alga Chondrus crispus was determined quantitatively. The inner cells contained more bromine than the epidermal cells: in the chloroplasts of the inner cells bromine concentrations of about 6% could be demonstrated.

Bromine↗
PubMed1977

Physico-chemical and immunological properties of allophycocyanins.

Allophycocyanins were purified from diverse cyanobacteria and one rhodophytan alga (Cyanidium caldarium). The native proteins are trimeric molecules with the structure (alpha beta)3. Representative native allophycocyanins and their alpha and beta subunits were characterized with respect to molecular weight, amino acid composition, isoelectric point, absorption and fluorescence spectra and immunological properties. All of the allophycocyanins studied were strikingly similar with respect to each of these properties. Renatured alpha and beta subunits of allophycocyanin were distinct immunologically from each other, and both cross-reacted with the antiserum to the native protein. Trimeric allophycocyanin was readily reconstituted from the purified alpha and beta subunits. Formation of hybrid allophycocyanins was demonstrated by direct isolation and characterization of the hybrid proteins and by immunological techniques. The results support the view that allophycocyanins are a highly conserved group of proteins.

Amino Acids↗
PubMed1978

Excitation energy transfer between pigment system II units in blue-green algae.

Efficiency in excitation energy transfer from closed to open reaction center II in blue-green and red algae was estimated by the method developed by Joliot and Joliot (C.R. Acad. Sci. (1964) 258, 4622--4625) after slight modification; the number of open reaction centers II was counted from the mean O2 yield of repetitive short flashes. The efficiency in energy transfer in Chlorella pyrenoidosa was the same in our measurement as that reported by Joliot and Joliot (0.55 +/- 0.02). However, the values obtained with four blue-green algae and one red alga were very small, in a range of 0.00--0.07. The low efficiency was always obtained independently of the size of the apparent photosynthetic unit which was varied by growth conditions. Results indicated that pigment system II forms a unit in which only one reaction center II is operative.

Cyanobacteria↗
PubMed1979

Side chain-hydroxylated sterols of the red alga Asparagopsis armata: significant products or artifacts due to autoxidation?

Sterols characterized by an allylic hydroxyl group in the side chain, such as stigmasta-5,28-diene-3 beta, 24 epsilon-diol (1), cholesta-5,23-diene-3 beta,25-diol (2) and cholesta-5,25-diene-3 beta,24 epsilon-diol (3), have been identified several times in various marine algae. Their origin was considered as doubtful: they could have been bona fide constituents of the alga, or be artifacts caused by autoxidation during the isolation process. We have shown that the dihydroxy steroids 2 and 3 can indeed be produced by the autoxidation of cholesta-5,24-dien-3 beta-ol (desmosterol) (5), but that they are nevertheless present in the taxonomic significance.

Cholestadienols↗
PubMed1979

The mutagenicity of natural products from marine algae.

5 polyhalogenated hydrocarbon natural products isolated from the marine red alga Plocamium spp. were tested for mutagenicity in the Ames reversion assay. All 5 of the compounds induced revertants in Salmonella typhimurium strains TA100 and TA1535, indicating the mutational events involved base substitutions. One of the compounds, designated cross-conjugated ketone, was shown to be almost 200 times more effective as a mutagen than was ethyl methanesulfonate.

Hydrocarbons, Halogenated↗
PubMed2026

Dietary soybean or seaweed (Kappaphycus sp.) modulates taste-related gene (tas1r1 and tas1r2.2) expression in Nile tilapia (Oreochromis niloticus).

Taste perception plays a central role in fish feeding behaviour by influencing feed recognition, intake, and nutrient sensing. As aquaculture increasingly adopts plant-based ingredients to replace fishmeal, understanding how these diets affect gustatory mechanisms is critical. This study evaluated TAS-family taste receptor genes in Nile tilapia (Oreochromis niloticus) fed nutritionally formulated diets containing fishmeal (TFM), soybean meal (TSB), red seaweed (Kappaphycus sp., TSW), alongside a natural meal (TNM) reference. Fish were reared for 62 days under controlled conditions, after which growth performance was evaluated, and tongue transcriptomes were analysed using RNA sequencing to identify diet-associated gene expression changes. Candidate TAS1R and TAS2R receptors were identified through conserved domain screening and phylogenetic validation, and differential expression analysis was performed using DESeq2. Growth performance did not differ significantly among diets, although the soybean group showed the highest weight gain. Under the conditions of this study, most taste-related genes remained transcriptionally stable across formulated diets, indicating limited responsiveness of the gustatory system to ingredient substitution. Transcriptional differences were mainly observed in comparisons involving the TNM (TSB vs TNM and TSW vs TNM), where tas1r1 was upregulated, suggesting altered amino acid sensing relative to the non-formulated diet. Among formulated diets, tas1r2.2 was upregulated in the TSW vs TFM comparison, indicating potential modulation of carbohydrate-related taste pathways associated with seaweed inclusion. No reliable TAS2R transcripts were detected, likely due to low expression or tissue-specific distribution. Overall, taste receptor expression in Nile tilapia appears resilient to dietary variation, with selective modulation of TAS1R genes providing molecular insight into chemosensory adaptation to sustainable feed ingredients.

Animals↗
PubMed2026

Genome-wide insights into the evolutionary and demographic history of the red alga Mazzaella laminarioides: Evidence for speciation with ancient migration along the southeast Pacific coast.

The mechanisms driving lineage divergence in red algae remain unexplored, despite the group's remarkable diversity and ancient evolutionary history. The red alga Mazzaella laminarioides, a Chilean intertidal species complex composed of three parapatric cryptic lineages (North, Center, South), offers a valuable system to evaluate these processes, as its life history combines severe dispersal limitation with a haploid-diploid cycle that may influence the emergence of reproductive barriers. We reconstructed its evolutionary history using whole-genome sequencing and nuclear genome assembly of representative individuals from each lineage. Phylogenomic analyses based on 1,507 single-copy orthologs recovered three deeply divergent lineages with limited nuclear discordance consistent with incomplete lineage sorting. For both splits, demographic modelling was most consistent with an Ancient Migration scenario, although support over strict isolation was moderate, suggesting that divergence may have begun with low asymmetric ancestral gene flow followed by subsequent loss of connectivity, demographic bottlenecks, and later population expansion. Coding sequence analyses revealed lineage-specific dN/dS heterogeneity; only one South-lineage locus passed FDR correction (metaxin-1, mitochondrial protein import), with two further South-lineage candidates in chlorophyll and heme biosynthesis falling below the FDR threshold. Together, these signals suggest that divergent selective pressures on energy acquisition may have contributed to divergence at the southern end of the distribution. These results add to the small but growing body of whole-genome data for red algae and, alongside recent macroalgal studies, suggest that ancestral connectivity could be a recurrent feature of lineage divergence even in marine organisms with extremely restricted dispersal.

Rhodophyta↗
PubMed1979

Paired-ion reversed-phase high-performance liquid chromatography of phenol sulfates in synthetic mixtures, algal extracts and urine.

Phenol sulfate esters have been analyzed by paired-ion reversed-phase high-performance liquid chromatography. The method provided direct, rapid chromatography of phenol sulfates in crude extracts of the red alga (Polysiphonia lanosa (2,3-dibromo-4,5-dihydroxybenzyl alcohol 1',4-disulfate), of the brown alga Ascophyllum nodosum (1,2,3,5-tetrahydroxybenzene 2,5-disulfate), and in rat urine (resorcinol mono- and disulfates). Detector response (254 nm) was linear within the approximate range from 30--125 ng to 5--10 microgram. Semipreparative scale chromatography provided sufficient amounts of purified phenol sulfates for further analysis by paper electrophoresis.

Animals↗