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Between 2023 and 2024, a type of green alga was observed for the first time settling on Oil-tea Camellia leaves and branches in the eastern Oil-tea Camellia planting area of Hainan Island, forming a layer of gray-green moss with a rough surface that seriously interfered with the leaves' normal photosynthesis. To further research the issue, this study used the plant photosynthesis measurement system and the paraffin sectioning technique to compare and analyze the changes in photosynthetic characteristics and anatomical structure of healthy and green algal-covered Oil-tea Camellia leaves. At the same time, the algal strain was effectively separated and purified using the plate delineation method, and its species classification was determined by combining morphological observation and molecular identification based on SSU-ITS sequences. The results of the study demonstrated that the coating of green alga facilitated the lignification of the leaf's epidermal cell walls. After being covered by the green alga, the intercellular CO2 concentration (Ci) increased significantly by 21.5%, while the net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) all significantly decreased by 72.8%, 30.4%, and 24.9%, respectively. More specifically, the green alga that covers the leaves of Oil-tea Camellia was identified as Desmodesmus armatus of Chlorophyta. Notably, the green alga had a long growth cycle, did not undergo a decline phase within one month, had an optimal growth pH of 11.0, and could flourish in excessively alkaline conditions. In conclusion, this study not only reported for the first time the phenomena of D. armatus infesting Oil-tea Camellia leave, but also showed its unique physiological and ecological properties, providing a foundation for future research on relevant prevention and control approaches. [ABSTRACT FROM AUTHOR]

Environmental context: The increasing global demand for platinum and palladium for the development of new technologies will likely enhance their biogeochemical mobility. However, our understanding of the environmental risks of these metals remains incomplete. To help fill this knowledge gap, we determined the toxicity of various forms of platinum and palladium on a green alga. We found that palladium was more toxic than platinum and that platinum toxicity depended on the form tested. Rationale: Chemical equilibrium-based models such as the biotic ligand model (BLM) can be used to predict metal toxicity towards aquatic organisms. However, some metals such as platinum (Pt) and to a lesser extent palladium (Pd) are known to be kinetically hindered, i.e. reactions between these elements and ligands in solution might be slow relative to the biota exposure time. The BLM applicability may thus be limited for these metals and their ecological risk assessment may require consideration of their initial form of entry in aquatic ecosystems. Methodology: This study investigates the relationship between inorganic Pt and Pd initial speciation and their bioavailability and toxicity toward the unicellular green alga Raphidocelis subcapitata. Chloro- or amino-coordinated Pt and Pd complexes such as PtIICl42−, PtIVCl62−, PtII(NH3)42+, PdIICl42− and PdII(NH3)42+ were examined in 96-h algae exposure experiments to determine growth inhibition and metal accumulation. Investigation of the complex stability over time of the tested complexes was carried out using spectrophotometry measurements and kinetic calculations. Results: Similar accumulation and no toxicity (half maximal effective concentration, EC50 > 150 µg L−1) were observed for both in our tested conditions. Nevertheless, evidence of PtIICl42− dissociation was observed whereas PtII(NH3)42+ was stable. Exposure to PtIVCl62− showed stronger algal growth inhibition (EC50 = 142 µg L−1) than exposure to PtIICl42− but similar accumulation. This phenomenon might be partly explained by the generation of free chloride radicals through PtIV reduction in the presence of light. Similar accumulation and toxicity were observed for both PdIICl42− (EC50 = 4.69 µg L−1) and PdII(NH3)42+ (EC50 = 2.40 µg L−1). Discussion: These results were coherent with the relatively rapid speciation changes of the PtII complexes as observed and modelled. We therefore conclude that the initial speciation of the studied chloro- and amino-coordinated PtII and PdII complexes is not a determining parameter of their accumulation and toxicity towards R. subcapitata. Environmental context. The increasing global demand for platinum and palladium for the development of new technologies will likely enhance their biogeochemical mobility. However, our understanding of the environmental risks of these metals remains incomplete. To help fill this knowledge gap, we determined the toxicity of various forms of platinum and palladium on a green alga. We found that palladium was more toxic than platinum and that platinum toxicity depended on the form tested. (Image credit: J. Michaud-Valcourt.) [ABSTRACT FROM AUTHOR]

The main component of microfossils in the bottom sediments of Reindeer Lake from Spitsbergen, documenting the almost 8,000-year history of this water body, are algae representing colonies of a very rare species Pediastrum orientale (Skuja) Jankovská et Komárek 1995 with only a very small (lower than 1%) admixture of other green algae species. It has also been recorded in other lake sediments in Spitsbergen. The specimens belong to the morphotype “b” of the species, known previously from the Scandinavian lakes. Due to its unique nature and scarce information on ecological conditions, this study analysed the palaeoenvironmental factors favouring the occurrence of Pediastrum orientale together with an assessment of its bioindication value. The affinity of the species to oligotrophic lakes, where blooms of this alga are observed, was confirmed. The presence of numerous colonies of Pediastrum orientale in fossil lake sediments can provide a rationale for inferring palaeoecological conditions, including the trophic state of water bodies, thus expanding knowledge of their evolutionary directions and documenting key events in the geological history of the catchment. Further studies of lake gyttjas in Spitsbergen should pay more attention to the taxonomic composition of Pediastrum and other green algae, as well as to the determinants of sediment deposition in different lake catchment environments.

Today, using CO2 in microalgae cultures has been increasing for different purposes. Microalgae have the potential to produce high-value products along with CO2 fixation. Dunaliella is a two- flagellate green microalga. The relatively good quality protein and fatty acid, besides lacking an indigestible cell wall make this alga an exceptional food in aquaculture and poultry fostering. In addition, there are many indigenous strains of algae with the advantage of adaptation to the regional climate condition. The main objective of this study was to evaluate the CO2 effect on the growth pattern and biochemical composition of Dunaliella sp. ABRIINW-I1 is native to Urmia Lake. Results showed that using CO2 in the culture not only affects the biomass concentration (1.06 g/l AFDW vs 0.54 g/l in the control experiment) and growth period (reaching the stationary phase in 7 days rather than 14 days in the control experiment); but also influences the chemical composition. It seems that during the cultivation time, the lipid content increased in the cost of carbohydrates (33.1%DW). Fatty acid analysis revealed an optimal combination of saturated and unsaturated acids with the dominance of C16 and C18 fatty acids. It seems that CO2 injection had no significant effect on the type of FA. The nutritional values of the studied strain were validated in this study, particularly when treated with CO2. The results demonstrated that utilizing CO2 in an algal culture could lead to decreased cost and energy requirements. [ABSTRACT FROM AUTHOR]

The accumulation of information on the geographical distribution range, genetic structure, and host utilization of the symbiont is important for studying how the symbiont spreads its distribution. Pseudocladophora conchopheria is a green alga that grows on the shells of intertidal gastropods distributed in the Japanese Archipelago, the Ryukyu Archipelago, and the southern part of Korean Peninsula. However, we discovered algae similar to P. conchopheria on the shells of gastropods from Vietnam. Therefore, species identification of the algae and the host gastropods was performed based on morphological observations and molecular genetic methods. As a result, the morphological characteristics of the algae were consistent with those of P. conchopheria, and the morphological characteristics of the host gastropods were consistent with those of Lunella granulata. Molecular genetic methods further supported these results of morphological identification. Interestingly, their algae were more closely related to P. conchopheria attached to L. correensis from the Sea of Japan rather than those attached to L. granulata from the Ryukyu Archipelago. These results suggest that P. conchopheria has expanded its distribution by utilizing multiple hosts and are explained on a wider scale than previous findings. [ABSTRACT FROM AUTHOR]

Marine algal lectins specific for high-mannose N-glycans have attracted attention because they strongly inhibit the entry of enveloped viruses, including influenza viruses and SARS-CoV-2, into host cells by binding to high-mannose-type N-glycans on viral surfaces. Here, we report a novel anti-influenza virus lectin (named HBL40), specific for complex-type N-glycans, which was isolated from a marine green alga, Halimeda borneensis. The hemagglutination activity of HBL40 was inhibited with both complex-type N-glycan and O-glycan-linked glycoproteins but not with high-mannose-type N-glycan-linked glycoproteins or any of the monosaccharides examined. In the oligosaccharide-binding experiment using 26 pyridylaminated oligosaccharides, HBL40 only bound to complex-type N-glycans with bi- and triantennary-branched sugar chains. The sialylation, core fucosylation, and the increased number of branched antennae of the N-glycans lowered the binding activity with HBL40. Interestingly, the lectin potently inhibited the infection of influenza virus (A/H3N2/Udorn/72) into NCI-H292 cells at IC50 of 8.02 nM by binding to glycosylated viral hemagglutinin (KD of 1.21 × 10−6 M). HBL40 consisted of two isolectins with slightly different molecular masses to each other that could be separated by reverse-phase HPLC. Both isolectins shared the same 16 N-terminal amino acid sequences. Thus, HBL40 could be useful as an antivirus lectin specific for complex-type N-glycans. [ABSTRACT FROM AUTHOR]

Caulerspiros A (1) and B (2), a new pair of α-tocopheroid isomers, with five known compounds (3-7) were isolated from the green alga Caulerpa racemosa var. turbinata. Their structures were elucidated by the method of comprehensive spectroscopy. The absolute configurations of 1 and 2 were established by the methods of ECD calculation and comparing with the previously reported literature. Compounds 1 and 2 represented the rare examples of α-tocopherol derivatives possessing a core unit of 1-oxaspiro[4.4]non 7-en-6-one. Additionally, the antibacterial activities of these seven compounds were also evaluated. However, none of them showed antibacterial activities with MIC values > 128 μg/ml. [ABSTRACT FROM AUTHOR]

Between 2023 and 2024, a type of green alga was observed for the first time settling on Oil-tea Camellia leaves and branches in the eastern Oil-tea Camellia planting area of Hainan Island, forming a layer of gray-green moss with a rough surface that seriously interfered with the leaves’ normal photosynthesis. To further research the issue, this study used the plant photosynthesis measurement system and the paraffin sectioning technique to compare and analyze the changes in photosynthetic characteristics and anatomical structure of healthy and green algal-covered Oil-tea Camellia leaves. At the same time, the algal strain was effectively separated and purified using the plate delineation method, and its species classification was determined by combining morphological observation and molecular identification based on SSU-ITS sequences. The results of the study demonstrated that the coating of green alga facilitated the lignification of the leaf’s epidermal cell walls. After being covered by the green alga, the intercellular CO2 concentration (Ci) increased significantly by 21.5%, while the net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) all significantly decreased by 72.8%, 30.4%, and 24.9%, respectively. More specifically, the green alga that covers the leaves of Oil-tea Camellia was identified as Desmodesmus armatus of Chlorophyta. Notably, the green alga had a long growth cycle, did not undergo a decline phase within one month, had an optimal growth pH of 11.0, and could flourish in excessively alkaline conditions. In conclusion, this study not only reported for the first time the phenomena of D. armatus infesting Oil-tea Camellia leave, but also showed its unique physiological and ecological properties, providing a foundation for future research on relevant prevention and control approaches.

The main component of microfossils in the bottom sediments of Reindeer Lake from Spitsbergen, documenting the almost 8,000-year history of this water body, are algae representing colonies of a very rare species Pediastrum orientale (Skuja) Jankovská et Komárek 1995 with only a very small (lower than 1%) admixture of other green algae species. It has also been recorded in other lake sediments in Spitsbergen. The specimens belong to the morphotype “b” of the species, known previously from the Scandinavian lakes. Due to its unique nature and scarce information on ecological conditions, this study analysed the palaeoenvironmental factors favouring the occurrence of Pediastrum orientale together with an assessment of its bioindication value. The affinity of the species to oligotrophic lakes, where blooms of this alga are observed, was confirmed. The presence of numerous colonies of Pediastrum orientale in fossil lake sediments can provide a rationale for inferring palaeoecological conditions, including the trophic state of water bodies, thus expanding knowledge of their evolutionary directions and documenting key events in the geological history of the catchment. Further studies of lake gyttjas in Spitsbergen should pay more attention to the taxonomic composition of Pediastrum and other green algae, as well as to the determinants of sediment deposition in different lake catchment environments. [ABSTRACT FROM AUTHOR]

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our research, we have developed novel bioplastics called "cell-plastics", in which a unicellular green algal cell serves as a fundamental resource. The production of the cell-plastics would be expected to reduce environmental impact due to the usage of a natural product. Herein, to overcome the mechanical strength of cell-plastics, we used thermosetting epoxy and urethane resins containing Chlorella sp. as the green algae. We successfully fabricated thermosetting resins with a Chlorella sp. content of approximately 70 wt% or more. IR measurements revealed that the chemical structure of an epoxide or isocyanate monomer mixed with Chlorella sp. was modified, which suggests that the resins were hardened by the chemical reaction. In addition, we investigated the effect of thermosetting conditions such as temperature and compression for curing both resins. It was revealed that the Young's moduli and tensile strengths were controlled by thermosetting temperature and compression, whereas the elongation ratios of the resins were constant at low values regardless of the conditions. [ABSTRACT FROM AUTHOR]

The current study included shedding light on one genus of green alga Dunaliella salina spread from the saline brine ponds, Basrah Governorate, southern Iraq. Morphological results showed all algal samples from different brine ponds sites in Basrah governorate were belong to the species D. salina, and the measured enviro-nmental factors are commensurate with the growth of this species especially salinity, due to its increasing growth compatible increasing salinity with significantly P≤0.05 at concentrations 0-15% of sodium chloride salt, which equaled a salinity level more than 4 times the salinity of sea water, which amounted to 150 g/L. finding showed the concentration 5% of sodium chloride is considered it is a suitable concentration for the growth of all alga samples with no significant differences P≤0.05 between the generation time (G) and constant growth (K) for all cultures samples. Finding was proven that all isolates of the different sites showed the ability to produce total carotene in response to an increase or decrease in salinity, as is the case in the salinity-free control group as an effort that requires the alga to produce carotene, and this is an important characteristic for this species as well. From these results, it can be concluded that all isolates of algae from different sites belong to only one species diagnosed in the current study.

The formation of ordered dolomite under Earth's surface conditions remains a challenge, although many researchers have now shown that microbes can facilitate the precipitation of this common mineral. This study provides the first evidence of dolomite biomineralization by the green alga Spirogyra (Zygnematales, Chlorophyta), a globally dispersed lacustrine genus. Microbial mats formed by Spirogyra occur in the hyperalkaline and ephemeral lake Caballo Alba, located in Central Spain and characterized by water solutions with high Mg/Ca ratios. Microscopic, geochemical, mineralogical and cytochemical studies have shown that accumulations of carbonates occur within different cells and locations of the alga. Biominerals mostly consist of single crystals of magnesian calcite and dolomite with variable proportions of Ca2+ and Mg2+. High‐resolution transmission electron microscopy and selected area electron diffraction patterns of the carbonates confirm the pervasive presence of super‐lattice reflections typical of ordered dolomite in compositions with greater than 32 mol% MgCO3. The curved surfaces of some carbonate crystals and their attachment to the organic surfaces represent imprints of a confined growth in compartments that act as a template for crystal nucleation and shape the crystals. Dyes reveal chemical differences in these compartments which explain the polymineral biomineralization and suggest that the alga do not strictly control the precipitation process. Zygnematales algae related with Spirogyra date back possibly to the Early Palaeozoic, thus suggesting that dolomite biomineralization could have been a common process through the Phanerozoic. This discovery provides new insight into the biotic formation of orderly dolomite and aids in the reconstructions of past lacustrine environments of dolomite deposition. [ABSTRACT FROM AUTHOR]

Chlorococcum is a coccoid green algal genus, which contains almost 50 species. The genus is polyphyletic, but in a traditional sense, the cells are coccoid and non-motile with a cup-shape chloroplast in the vegetative stage, while the spores have chlamydomonad appearance. They are distributed worldwide mainly in terrestrial habitats, and the biotechnological potential of several strains has been reported. In this study, three new green algal strains from a shallow, temporary freshwater lake in Hungary are characterized using microscopic (light and transmission electron microscopy) and DNA-based methods (phylogenetic analysis of the ribosomal ITS region, the 18S ribosomal RNA and rbcL genes, and ITS secondary structure comparison). Based on the obtained results, one of the three new isolates is considered to represent a new species, which is described here as Chlorococcum szentendrense sp. nov. [ABSTRACT FROM AUTHOR]

The current study included shedding light on one genus of green alga Dunaliella salina spread from the saline brine ponds, Basrah Governorate, southern Iraq. Morphological results showed all algal samples from different brine ponds sites in Basrah governorate were belong to the species D. salina, and the measured enviro-nmental factors are commensurate with the growth of this species especially salinity, due to its increasing growth compatible increasing salinity with significantly P≤0.05 at concentrations 0-15% of sodium chloride salt, which equaled a salinity level more than 4 times the salinity of sea water, which amounted to 150 g/L. finding showed the concentration 5% of sodium chloride is considered it is a suitable concentration for the growth of all alga samples with no significant differences P≤0.05 between the generation time (G) and constant growth (K) for all cultures samples. Finding was proven that all isolates of the different sites showed the ability to produce total carotene in response to an increase or decrease in salinity, as is the case in the salinity-free control group as an effort that requires the alga to produce carotene, and this is an important characteristic for this species as well. From these results, it can be concluded that all isolates of algae from different sites belong to only one species diagnosed in the current study. [ABSTRACT FROM AUTHOR]

Oligosaccharides offer beneficial effects on immune system and gut health, such as immunomodulatory activity, anticancer activity, and complement activation. Functional oligosaccharides are widely found in plants, algae, bacteria, and higher fungi. The consumption of functional oligosaccharides can reduce the risk of lifestyle-related diseases, such as cardiovascular disease, cancer, obesity and type 2 diabetes. Marine macroalgae possess tremendous nutritional value and have been well-known to cure and prevent the chronic metabolic diseases. An increased interest in various bioactive natural products from marine macroalgae, as a potential source of effective agents, has been observed in recent years. Especially, green algae have attracted attentions for their important functional properties and potential biological applications. The effects of marine green algal oligosaccharides may delay the development of chronic metabolic diseases such as diabetes, and alter the metabolic abnormalities through various mechanisms of actions. Marine green algal oligosaccharides used to prevent and manage diabetes. The excellent performance was based on their chemical structures and glycosidic linkages. Our research is focus on structures, accessible sources, physiological and chemical characteristics, and potential health benefits of green algal functional oligosaccharides. Moreover, the project aims to to carry out research on new key gene mining and regulation mechanism of marine green algal functional oligosaccharides to dietary interventions for glucose metabolism. Our group engages in the nutritional evaluation research of functional components from marine algae and has achieved a series of original results: to firstly report the largest gram scale production of fucosylated oligosaccharide lacto-N-fucopentaose I, to firstly discovered the COL1A1 as one potential new biomarker and therapeutic target for type 2 diabetes, to reveal the new mode of regulation of algal oligosaccharides on glycometabolism network based on microRNAs, and to elucidate systematically molecular mechanisms of marine algal oligosaccharides to regulate glucose metabolism via mediating intestinal flora. These results make the important breakthrough in the theoretical basis of algal food nutrition and successfully realize them transformation and application. [ABSTRACT FROM AUTHOR]

We have previously created and expressed a chimeric polypeptide joining the PsaC subunit of Photosystem I (PSI) to the HydA2 hydrogenase of Chlamydomonas reinhardtii and demonstrated that it assembles into the PSI complex and feeds electrons directly to the hydrogenase domain, allowing for prolonged photobiological hydrogen production. Here we describe a new PSI-hydrogenase chimera using HydA1, the more abundant and physiologically active endogenous hydrogenase of this alga. When the PsaC-HydA1 polypeptide was expressed in a C. reinhardtii strain lacking endogenous hydrogenases, it was assembled into active PSI-HydA1 complexes that were accumulated at a level ∼75% that of PSI, which is ∼5 times higher than the PSI-HydA2 chimera. Hydrogen production by the chimera could be restored after complete inactivation by oxygen without requiring new synthesis of PSI or the PsaC-HydA1 polypeptide, demonstrating that the complex could be repaired in vivo. The PSI-HydA1 chimera reduces ferredoxin in vivo to such an extent that it can drive the Calvin-Benson-Bassham cycle, leading to high O 2 production rates, and eventually resulting in inactivation of the hydrogenase; use of media that drastically diminished CO 2 fixation and an O 2 -scavenging material allowed H 2 production for at least 4 days. • The PsaC-HydA1 fusion is expressed and assembles on photosystem I in vivo. • The chimeric PSI-HydA1 complex is accumulated at levels approaching wild-type PSI. • Light-dependent H 2 evolution switches to H 2 uptake upon CO 2 fixation. • PsaC-HydA1 can be reactivated in vivo after O 2 inactivation. [ABSTRACT FROM AUTHOR]

Mass production of microorganisms, algae among them, for new bioactive compounds and renewable innovative products is a current issue in biotechnology. The greatest challenge of basic research on this topic is to find the best solution for both physiology and scalability. In this study, the main goal was to highlight the contradictions of physiological and technological optimization in the same, relatively small, laboratory scale. The green alga Monoraphidium pusillum (Printz) Komárková-Legnorová was cultured in a conventional Erlenmeyer flask (as air bubbled in a tank-type photobioreactor) and in a hybrid (fermenter type + helical tubular type) photobioreactor of the same volume (2.8 L). Higher cell numbers from 1.7–2.3-fold, 2–2.8-fold higher dry masses, and 1.9–2.6-fold higher total lipid contents (mg·L−1) were measured in the tank reactor than in the hybrid reactor. Cultures in the conventional tank reactor were characterized with better nutrient utilization (42.8–77.7% higher phosphate uptake) and more diverse lipid composition than in the hybrid reactor. The study highlights that well-scalable arrangements and settings could be not optimal (or unsuitable in some cases) from a physiological point of view. The results suggest certain developmental directions for complex, well-scalable devices and highlight the importance of testing the gained physiological optima on these systems. [ABSTRACT FROM AUTHOR]

SUMMARY: Although the green seaweed Ulva is one of the most common seaweeds in the coastal regions with well‐studied ecological characteristics, few reverse genetic technologies have been developed for it. The clustered regularly interspaced short palindromic repeats (CRISPR)‐Cas9 system is a simple genome‐editing technology based on a ribonucleoprotein (RNP) complex composed of an endonuclease and programmable RNA to target particular DNA sequences. Genome editing makes it possible to generate mutations on a target gene in non‐model organisms without established transgenic technologies. In this study, we applied the CRISPR‐Cas9 RNP genome‐editing system to the green seaweed Ulva prolifera, using polyethylene glycol (PEG)‐mediated transfection. Our experimental system disrupts a single gene (UpAPT) encoding adenine phosphoribosyl transferase (APT) and generates a resistant phenotype for gametophytes cultured in a medium with toxic compound 2‐fluoroadenine. The PEG‐mediated transfection used for gametes resulted in 2‐fluoroadenine‐resistant strains containing short indels or substitutions on UpAPT. Our results showed that the CRISPR‐Cas9 system with PEG‐mediated transfection was efficient for genome editing in Ulva. [ABSTRACT FROM AUTHOR]

Several theories for aging are constantly put forth to explain the underlying mechanisms. Oxidative stress, DNA dysfunction, inflammation, and mitochondrial dysfunction, along with the release of cytochrome c are some of these theories. Diseases such as type 2 diabetes mellitus, intestinal dysfunction, cardiovascular diseases, hepatic injury, and even cancer develop with age and eventually cause death. Ulva polysaccharides, owing to their special structures and various functions, have emerged as desirable materials for keeping healthy. These polysaccharide structures are found to be closely related to the extraction methods, seaweed strains, and culture conditions. Ulvan is a promising bioactive substance, a potential functional food, which can regulate immune cells to augment inflammation, control the activity of aging-related genes, promote tumor senescence, enhance mitochondrial function, maintain liver balance, and protect the gut microbiome from inflammatory attacks. Given the desirable physiochemical and gelling properties of ulvan, it would serve to improve the quality and shelf-life of food. • The theories of aging were discussed and summarized following in time. • The unhealthy aging of the body can be a huge damage to human beings. • The structural characteristics and healthy aging effects of ulvan were described. • More attentions and technics were necessary to investigate the healthy aging of ulvan. [ABSTRACT FROM AUTHOR]

Ulva is a green seaweed that is widely distributed in coastal areas around the world, and genomic information has been reported for several species. However, research on reverse genetics methods is still in its early stages. Although our group has recently achieved efficient knockout of Ulva by introducing Cas9 ribonucleoprotein (RNP) through the PEG method, a precise knock-in transformation method is needed to understand gene and protein functions. Here, we report the development of a targeted insertional mutagenesis method by transfection of Cas9 RNP, donor dsDNA, and single-stranded DNAs homologous to the DSB site created by Cas9 and donor dsDNA. The target gene was RbcS , a well-known high-expression gene, and we attempted to knock in the EGFP or 2A peptide- EGFP sequence at the C-terminus region. This method was also applied to the adenine phosphoribosyltransferase (APT) gene, enabling selection by the toxic compound 2-fluoroadenine. A longer DNA fragment (2.6 kb) expressing EGFP under the RbcS promoter was inserted at the DSB site on the APT locus. As a result, EGFP knock-in transformants were obtained, and the transformant progeny exhibited high EGFP expression levels for several generations. Our method greatly advances the genetic engineering and functional analysis of target genes in Ulva. • Genetic transformation in seaweed remains a challenge. • Cas9 RNP, donor dsDNA, and single-stranded DNAs enable a targeted insertional mutagenesis in Ulva. • Knock-in mutants maintain EGFP expression for several generations. • This methodology marks a significant advancement in biotechnological research for seaweeds. [ABSTRACT FROM AUTHOR]

A novel photoreceptor dualchrome 1 (DUC1), containing a fused structure of cryptochrome and phytochrome, was discovered in the marine green alga Pycnococcus provasolli. The DUC1 phytochrome region (PpDUC1-N) binds to the bilin (linear tetrapyrrole) chromophores, phytochromobilin (PΦB) or phycocyanobilin (PCB), and reversibly photoconverts between the orange-absorbing dark-adapted state and the far-red-absorbing photoproduct state. This contrasts with typical phytochromes, which photoconvert between the red-absorbing dark-adapted and far-red-absorbing photoproduct states. In this study, we examined the molecular mechanism of PpDUC1-N to sense orange light by identifying the chromophore species synthesized by P. provasolli and the amino acid residues within the PpDUC1-N responsible for sensing orange light in the dark-adapted state. We focused on the PcyA homolog of P. provasolli (PpPcyA). Coexpression with the photoreceptors followed by an enzymatic assay revealed that PpPcyA synthesized PCB. Next, we focused on the PpDUC1-N GAF domain responsible for chromophore binding and light sensing. Ten amino acid residues were selected as the mutagenesis target near the chromophore. Replacement of these residues with those conserved in typical phytochromes revealed that three mutations (F290Y/M304S/L353M) resulted in a 23-nm red-shift in the dark-adapted state. Finally, we combined these constructs to obtain the PΦB-binding F290Y/M304S/L353M mutant and a 38-nm red-shift was observed compared with the PCB-binding wild-type PpDUC1. The binding chromophore species and the key residues near the chromophore contribute to blue-shifted orange light sensing in the dark-adapted state of the PpDUC1-N., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.)

Mass production of microorganisms, algae among them, for new bioactive compounds and renewable innovative products is a current issue in biotechnology. The greatest challenge of basic research on this topic is to find the best solution for both physiology and scalability. In this study, the main goal was to highlight the contradictions of physiological and technological optimization in the same, relatively small, laboratory scale. The green alga Monoraphidium pusillum (Printz) Komárková-Legnorová was cultured in a conventional Erlenmeyer flask (as air bubbled in a tank-type photobioreactor) and in a hybrid (fermenter type + helical tubular type) photobioreactor of the same volume (2.8 L). Higher cell numbers from 1.7–2.3-fold, 2–2.8-fold higher dry masses, and 1.9–2.6-fold higher total lipid contents (mg·L−1) were measured in the tank reactor than in the hybrid reactor. Cultures in the conventional tank reactor were characterized with better nutrient utilization (42.8–77.7% higher phosphate uptake) and more diverse lipid composition than in the hybrid reactor. The study highlights that well-scalable arrangements and settings could be not optimal (or unsuitable in some cases) from a physiological point of view. The results suggest certain developmental directions for complex, well-scalable devices and highlight the importance of testing the gained physiological optima on these systems.

Carnosine, a dipeptide composed of β-alanine and histidine, is predominantly found in animals such as mammals, birds, and fish, with no known presence in plants, microalgae, and other organisms. It can undergo methylation to produce anserine, β-alanyl- N -methyl-L-histidine. These imidazole peptides are known for their antioxidative properties and fatigue recovery effects. The synthesis of carnosine is catalyzed by carnosine synthase, encoded by the ATPGD1 or CARNS1 gene. Recently, homologous proteins to carnosine synthase have been reported from several microalgal genomes, although their biological functions remain unknown. In this study, we investigated the role of carnosine synthase-like protein in the green alga Monoraphidium braunii SAG 48.87. Initially, we examined the accumulation of carnosine and anserine in M. braunii cells cultivated under various conditions. Interestingly, salt stress induced the accumulation of anserine. The cells treated with 420 mM NaCl accumulated 38.3 μg g−1 dry weight (DW) of anserine. Expression of ATPGD1a , putatively annotated as a carnosine synthase gene, was induced under salt stress conditions, while expression of ATPGD1b was downregulated. The Escherichia coli cells expressing the recombinant ATPGD1a primarily accumulated anserine (269.9 μg g−1 DW) and a small amount of carnosine, although we could not confirm any carnosine or anserine synthesis by the purified recombinant protein. These findings suggest that the carnosine synthase homolog in microalgae may play a role in synthesizing imidazole dipeptides, and anserine could serve as a salt protective agent and help stabilize cellular functions, particularly under salt conditions. This is the first observation of the synthesis of the imidazole dipeptide from any organism except animals and anserine protecting from salt stress. • We found anserine in the cells of a green alga Monoraphidium braunii. • Salt stress induced the accumulation of anserine in M. braunii. • Applying anserine or carnosine relieved from the salt stress. • A gene for carnosine synthase-like protein, ATPGD1a , induced under salt. • Expression of ATPGD1a in Escherichia coli produced anserine. [ABSTRACT FROM AUTHOR]

Genome sequence of an ulvan-degrading bacterium, Vibrio sp. strain 10N, is presented. The genome is 5,358,550 bp with a G + C content of 46.5%. A total of 4,712 coding sequences, including two novel ulvan lyase genes encoding a BNR4 and a glycoside hydrolase (GH88) motif, are known to be involved in the degradation of green algae., Competing Interests: The authors declare no conflict of interest.

DEAE-52 and Sephadex G-100 columns were used to isolate Enteromorpha prolifera polysaccharide (EPP), which contains α-L-Rha p -(1 → 4)-α-L-Ara p -(1 → 2)-α-L-Rha p -(1 → 3)-β-D-Gal p -(1 → structural fragment, along with α-L-Rha p -(1 → and →2)-α-L-Rha p -(1 → 3)-β-D-Glc p A-(1 → side bonds that connect to →3,6)-β-D-Gal p -(1→. The anti-ageing and hypoglycemic activities of EPP were assessed using an ageing diabetic mice model, and the revealed that EPP could improve glucose metabolism-associated parameters and inhibit the expression of ageing associated genes, including p16INK4a, p38 MAPK, NOX-1, VEGF, and AGER, thus preventing liver damage. Moreover, gut microbiota profiling revealed that EPP significantly increased the abundances of o_Lactobacillaceae , c_Bacilli , f_Lactobacillaceae , g_Lactobacillus , and p_Firmicutes, showing that EPP has a probiotic effect on enhancing the beneficial microbiota in ageing diabetic mice. In summary, EPP might serve as a potential bioactive compound to alleviate hyperglycaemia and ageing in diabetic in mice and further clinical studies are required to verify these effects. [ABSTRACT FROM AUTHOR]

Fluorescence-spectral microscope observations of photosynthetic organisms at cryogenic temperatures have the ability to spectrally resolve the two photosystems (PSs) and thus provide a powerful tool to elucidate the functional analysis of photosynthesis in vivo. In the present study, a measurement channel of the fluorescence lifetime at 680 nm was added to the cryo-microscope system previously developed by the authors. This provides access to information on the functional state of the light-harvesting system in living cells during regulation by a mechanism called state transitions. The observations of state1-locked and state2-locked Chlamydomonas cells at 80 K enabled us to identify a component showing rapidly decaying fluorescence with a lifetime of ca. 3 ps and emitting at around 676 nm. The component was assigned to the light-harvesting complex II (LHCII) that is isolated from both PSs and in a quenched state, probably due to the formation of aggregates. Simultaneous spectral observations revealed the accumulation of this free LHCII in the photosystem I (PSI)–enriched region within each state2-locked cell. To the best of our knowledge, this is the first in-vivo observation which suggests the localization of the quenched LHCII aggregates. • Fluorescence lifetime imaging technique was combined with the custom-built cryo-microscope technique. • Simultaneous detection of local fluorescence spectra at low temperature enabled to visualize the segregation of PSs. • The developed system was used to analyze the activity of LHC at various subdomains of chloroplast during state transitions. • The observations revealed that highly quenched LHCs are accumulated in PSI-rich region in state2. [ABSTRACT FROM AUTHOR]

As algae are extremely sensitive to heavy-metal ions and can be critical biological indicators in the heavy-metal toxicity analyses conducted by environmental health researchers, this paper explores the sensitivity to temporal toxicity of three species of green algae: Scenedesmus obliquus , Chlorella pyrenoidosa , and Selenastrum capricornutum . The method of time-dependent microplate toxicity analysis was used to systematically investigate the changes in the toxicities of the three green-algae species induced by different concentrations of cadmium (Cd). The chlorophyll a content, antioxidant enzyme activity, and malondialdehyde (MDA) content in the algae were analyzed to explore the mechanism of Cd toxicity after 96 h of exposure. The results showed that the toxic effects of Cd on the three algae species were time-dependent. By comparing the toxic effect of Cd, indicated by pEC 50 (the negative logarithm of EC 50 ), on the algae species at four durations of exposure (24, 48, 72, and 96 h), this study found that the indicator organisms had different sensitivities to Cd. The order of sensitivity was C. pyrenoidosa > S. obliquus > S. capricornutum . Cd exposure had significant effects on the chlorophyll a and MDA content and on the enzyme activity of superoxide dismutase (SOD) and catalase (CAT) in the algae species. The chlorophyll a content in the cells of the algae decreased with increasing Cd concentration. The enzyme activity of CAT and content of MDA increased with increasing Cd concentration, which indicated that Cd had an oxidative stress effect on the three algae species.