Green Algae Research Articles

Towards sustainable biocontrol: inhibition of soil borne fungi by microalgae from harsh environments.

Using microorganisms as biocontrol agents against soilborne plant pathogens is a promising alternative to chemical pesticides. However, only some biocontrol agents have proven effective under field conditions. This study explores the potential of highly resilient microalgae isolated from harsh environments, such as Biological Soil Crusts and agricultural fields in semi-arid regions, as a novel and sustainable approach to biocontrol. Fifty-nine microalgal strains, including thirteen cyanobacteria and forty-six green algae, were isolated and identified. Dual-culture plate assays and toxicity tests of microalgal growth media were conducted to evaluate the antifungal activity of the isolates against eight representative soilborne pathogens. The results showed that many microalgae strains exhibited significant inhibitory effects on the growth of specific fungal pathogens, although the activity varied among different microalgal strains and pathogen species. Some strains even promoted the growth of certain fungi. The lack of a clear pattern in the antifungal activity highlights the complexity and specificity of the interactions between microalgae and soilborne pathogens. An "Inhibition Effectiveness" metric was developed to quantify biocontrol potential based on fungal growth inhibition. The green algal genus Desmodesmus, particularly Desmodesmus subspicatus isolates, showed higher antifungal efficacy than other genera. While the inhibitory mechanisms remain unclear, the results demonstrate the promising biocontrol capabilities of microalgae from extreme environments like BSCs. Further research could unlock novel opportunities for sustainable disease management by harnessing specific microalgal strains or synergistic strain combinations targeting soilborne pathogens.

Unlocking the potential of Spirulina microalgae: Cultivating in wastewater treatment for sustainable biofuel production

Municipal wastewater, known for its high nitrogen and phosphorus levels, disrupts natural biogeochemical cycles. However, these nutrients are vital for cultivating green algae, which show potential as a sustainable energy source. In this study, Spirulina microalgae biomass was cultivated from diluted municipal wastewater and converted into biofuel to assess its compatibility with conventional diesel applications. Algae growth rate, nutrient removal from wastewater, and proximate and ultimate analyses of the biomass were conducted. Elemental, functional group, and chemical analyses of the biodiesel were also performed using an elemental analyzer, Fourier-transform infrared (FTIR) spectroscopy, and Gas Chromatography-Mass Spectrometry (GC-MS), respectively. Results showed effective removal of calcium, magnesium, potassium, and nitrogen nutrients by 44.7%, 71.7%, 50%, and 55.6%, respectively, through algae cultivation. Proximate and ultimate analyses confirmed the biomass's energy content and efficiency for energy production. Elemental analysis of biodiesel revealed significant contributions of carbon, hydrogen, and oxygen, while FTIR and GC-MS analyses identified carbon-based components and methyl esters as major constituents, respectively. Physicochemical properties of algae biodiesel met ASTM D6751 limits. This comprehensive assessment suggests that Spirulina algae from wastewater treatment holds promise as a viable energy source for diesel applications.

Biotesting of decabromodiphenyl oxide using a multi-component test system

The results of biotesting of decabromodiphenyl oxide using a multicomponent test sys- tem are presented. It has been demonstrated that its aqueous solutions exhibit a reverse dose- dependent effect in stimulating the growth of colonies of the green algae Chlorella vulgaris and show no signs of toxic effects on Daphnia magna. During the thermal decomposition of decabro- modiphenyl oxide at a temperature of 400°C, a mixture of products is formed, one of which is bromine. The decomposition product is released into the air and possesses toxic properties, as evi- denced by stimulation of the growth of colonies of the green algae Chlorella vulgaris, as well as the death and growth abnormalities of Planorbis mollusk embryos. Therefore, water samples con- taining decabromodiphenyl oxide can be assessed for toxicity by biotesting methods, using cul- tures of green algae Chlorella vulgaris and 24-hour-old Planorbis embryos as test subjects. It is noteworthy that in the context of the prevailing perception of the safety of decabromodiphenyl ox- ide, based on its poor water solubility and low toxicity to biological organisms, there arises a need to study embryotoxic effects of the thermal decomposition products on both animals and humans.

Screening clusters of charged residues in plants’ mitochondrial proteins and biological significance

Protein function is dependent on charge interactions and charge biased regions, which are involved in a wide range of cellular and biochemical processes. We report the development of a new algorithm implemented in Python and its use to identify charge clusters CC (NegativeCC: NCC, PositiveCC: PCC and MixedCC: MCC) and compare their presence in mitochondrial proteins of plant groups. To characterize the resulting CC, statistical, structural and functional analyses were conducted. The screening of 105 399 protein sequences showed that 2.6 %, 0.48 % and 0.03 % of the proteins contain NCC, PCC and MCC, respectively. Mitochondrial proteins encoded by the nuclear genome of green algae have the biggest proportion of both PCC (1.6 %) and MCC (0.4 %) and mitochondrial proteins coded by the nuclear genome of other plants group have the highest portion of NCC (7.5 %). The mapping of the identified CC showed that they are mainly located in the terminal regions of the protein. Annotation showed that proteins with CC are classified as binding proteins, are included in the transmembrane transport processes, and are mainly located in the membrane. The CC scanning revealed the presence of 2373 and 784 sites and 192 and 149 motif profiles within NCC and PCC, respectively. The investigation of CC within pentatricopeptide repeat-containing proteins revealed that they are involved in correct and specific RNA editing. CC were proven to play a key role in providing insightful structural and functional information of complex protein assemblies which could be useful in biotechnological applications.

Photoprotective activities of Capsosiphon fulvescens in UVB-induced SKH-1 mice and human keratinocytes.

Capsosiphon fulvescens (CF) is a green alga widely consumed in East Asian countries, particularly in Korea. It has a rich composition of vitamins, minerals, dietary fibers, and bioactive compounds, which contribute to its multiple therapeutic properties. Its application ranges from acting as an antioxidant and anti-inflammatory agent to supporting the skin system. Despite these benefits of CF, the effects and mechanisms of action related to photoaging of the skin have not yet been elucidated. To investigate the photoprotective effects of CF against photoaging, both animal (SKH-1 mouse) and cell models (HaCaT cell line) were used in this study. As a result, administering the CF extract over a period of 10weeks, which included times of Ultraviolet B (UVB) exposure, significantly reduced erythema and various UVB-induced skin changes, such as wrinkle formation, and the thickening of the epidermis and dermis, as well as alterations in the length and depth of wrinkles. Furthermore, our investigation into CF extract's antiwrinkle properties revealed its efficacy in enhancing skin hydration and collagen content, counteracting the collagen depletion and moisture loss induced by UVB radiation. Also, the fact that the levels of p-ERK, p-p38, and p-JNK proteins went down shows that the CF extract might have a controlling effect on the MAPK signaling pathways. Our findings suggest that CF holds significant potential for preventing photoaging, providing a foundation for the development of functional foods or botanical drugs targeting skin aging and related skin disorders. PRACTICAL APPLICATION: This research proved that Capsosiphon fulvescen, a green alga widely consumed in East Asian countries, provides photoprotective activities against UV-induced skin aging. Therefore, Capsosiphon fulvescen can be utilized as functional foods or botanical drugs targeting skin aging and related skin disorders.

Comparative plastome and mitogenome analyses indicate that the marine prasinophyte green algae Pycnococcus provasolii and Pseudoscourfieldia marina (Pseudoscourfieldiophyceae class nov., Chlorophyta) represent morphotypes of the same species.

The marine prasinophyte green algae Pycnococcus provasolii and Pseudoscourfieldia marina represent the only extant genera and known species of the Pycnococcaceae. However, their taxonomic status needs to be reassessed, owing to the very close relationship inferred from previous sequence comparisons of individual genes. Although Py. provasolii and Ps. marina are morphologically different, their plastid rbcL and nuclear small subunit rRNA genes were observed to be nearly or entirely identical in sequence, thus leading to the hypothesis that they represent distinct growth forms or alternate life-cycle stages of the same organism. To evaluate this hypothesis, we used organelle genomes as molecular markers. The plastome and mitogenome of Ps. marina UIO 007 were sequenced and compared with those available for two isolates of Py. provasolii (CCMP 1203 and CCAP 190/2). The Ps. marina organelle genomes proved to be almost identical in size and had the same gene content and gene order as their Py. provasolii counterparts. Single nucleotide substitutions and insertions/deletions were localized using genome-scale sequence alignments. Over 99.70% sequence identities were observed in all pairwise comparisons of plastomes and mitogenomes. Alignments of both organelle genomes revealed that Ps. marina UIO 007 is closer to Py. provasolii CCAP 190/2 than are the two Py. provasolii strains to one another. Therefore, our results are not consistent with the placement of Ps. marina and Py. provasolii strains into distinct genera. We propose a taxonomic revision of the Pycnococcaceae and the erection of a new class of Chlorophyta, the Pseudoscourfieldiophyceae.

Iron-Sulfur Peptides Mimicking Ferredoxin for an Efficient Electron Transfer to Hydrogenase.

In the green alga Chlamydomonas reinhardtii, hydrogenase HydA1 converts protons and electrons to H2 at the H-cluster, which includes a [4Fe-4S] cluster linked to a [2Fe] cluster. The yield of H2 is limited by the electron transfer to HydA1, mediated by the iron-sulfur unit of a photosynthetic electron transfer ferredoxin (PetF). In this study, I have investigated by molecular dynamics and the hybrid quantum mechanics/molecular mechanics method two canonical iron-sulfur peptides (PM1 and FBM) that hold potential as PetF replacements. Using a docking approach, I predict that the distance between the two iron-sulfur clusters in FBM/HydA1 is shorter than in PM1/HydA1, ensuring a greater electron transfer rate. This finding is in line with the reported higher H2 production rates for FBM/HydA1. I also show that the redox potential of these peptides, and therefore their electron transfer properties, can be changed by single-residue mutations in the secondary coordination sphere of their cluster. In particular, I have designed a PM1 variant that disrupts the hydrogen-bonding network between water and the cluster, shifting the redox potential negatively compared to PM1. These results will guide experiments aimed at replacing PetF with peptides that can unlock the biotechnological potential of the alga.

Phytochromobilin Binding and Specific Amino Acid Residues Near The Chromophore Contribute To Orange Light Perception By The Dualchrome Phytochrome Region.

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.

Structural characteristics of sulfated xylogalactomannan isolated from Caulerpa okamurae and its anticoagulant activity

Due to wonderful taste, rich nutrition and biological functions, many marine green algae in the genus Caulerpa have been recently developed as candidates for green caviar. A novel water-soluble sulfated xylogalactomannan CO-0-1 was obtained from the green algae Caulerpa okamurae. CO-0-1 was mainly composed of mannose (Man), galactose (Gal), and xylose (Xyl) at the ratio of 4.4:4.0:1.4 with the molecular weight at 470 kDa and the sulfate content at 12.78 %. The sulfated xylogalactomannan had Man at the backbone with →4)-β-D-Manp-(1→ and →2)-β-D-Manp-(1→ as the main chain and branches at O-3 position. The side chains contained →3)-β-D-Galp-(1→ and minor →2)-β-D-Xylp(1→. The sulfate groups only distributed at the side chains and at O-6 position of →3)-β-D-Galp-(1→ and O-4 position of (1→2)-β-D-Xylp. The anticoagulant activity indicated that CO-0-1 displayed intrinsic anticoagulant and specific anti-thrombin activities. The investigation expanded the utilization and development scene and scope of the green algae Caulerpa okamurae.

Classification of rock types of porous limestone reservoirs: case study of the A oilfield

Rock types with similar lithological components and pore structures form the basic units of porous limestone reservoirs; this influences the reservoir evaluation efficiency and water injection development. As the main oil and gas pay zone in central Iraq, the Cretaceous Khasib Formation reservoirs are influenced by deposition, dissolution, and cementation. There is strong vertical heterogeneity in the most important zone of the Kh2 layer, with diverse rock types and complex pore structures. Based on core observation and casting thin-section identification, the Kh2 layer in the study area was divided into eight lithofacies types as argillaceous bioclastic wackestone, planktic foraminiferium wackestone, lamellar bioclastic wackestone, intraclastic–bioclastic packstone, patchy green algae packstone, green algae and pelletoid packstone, benthic foraminiferium–bioclastic packstone, and intraclastic grainstone. Along with the reservoir void space types of the lithofacies, capillary pressure curves are used to quantitatively analyze the throat and pore features of the different lithofacies. From the porosity–permeability cross-plot characteristics and distribution of pore types, 14 petrophysical facies are obtained. Finally, based on the differences between the lithofacies and petrophysical facies, the Kh2 member is divided into 13 rock types with different geological origins and petrophysical characteristics. Among these, the rock type RT1-8-14 has the best and rock type RT1-1-1 has the worst physical properties among the reservoir rock types. This study provides an optimization method for carbonate reservoir evaluation and is expected to be beneficial for efficient development of similar carbonate reservoirs.

Therapeutic Efficacy of Spirulina Algae and N-Acetylcysteine in COVID-19 Hospitalized Patients: A Randomized Phase II Clinical Trial

Background: Spirulina algae are widely used in food, cosmetic, and dietary applications, and laboratory and clinical studies have reported their antiviral and immune-enhancing properties. Aim: We aimed to evaluate the prescription of spirulina, a safe food supplement with antiviral properties, and N-acetylcysteine in the treatment of hospitalized patients with Coronavirus Disease 2019 (COVID-19). Materials and Methods: This study was conducted as a multicenter, randomized, single-masked, open-label phase II clinical trial on 66 patients with COVID-19. Patients were randomly assigned to two intervention groups and one control group. The intervention groups were defined as follows: one group received spirulina algae (23 people), and the other group received N-acetylcysteine plus spirulina algae (21 people). In the control group (22 people), the patients only received the national standard treatment for COVID-19. The intervention groups were prescribed 80 mg/kg of spirulina green algae daily. Results: The duration of hospitalization (P = 0.874), Intensive Care Unit (ICU) admission (P = 0.320), and mortality (P = 0.320) of patients between the three groups did not show any significant difference. Side effects, including headache (P = 0.022) and nausea (P = 0.039), were significantly less common in the control group. No statistically significant difference was observed regarding the frequency of symptoms after discharge in the three-month follow-up (P = 0.420). Conclusion: Our study showed that administering spirulina with or without N-acetylcysteine did not affect the length of hospitalization, ICU admission, mortality, and the frequency of symptoms or long COVID.

ROS-mediated thylakoid membrane remodeling and triacylglycerol biosynthesis under nitrogen starvation in the alga Chlorella sorokiniana.

Many microbes accumulate energy storage molecules such as triglycerides (TAG) and starch during nutrient limitation. In eukaryotic green algae grown under nitrogen-limiting conditions, triglyceride accumulation is coupled with chlorosis and growth arrest. In this study, we show that reactive oxygen species (ROS) actively accumulate during nitrogen limitation in the microalga Chlorella sorokiniana. Accumulation of ROS is mediated by the downregulation of genes encoding ROS-quenching enzymes, such as superoxide dismutases, catalase, peroxiredoxin, and glutathione peroxidase-like, and by the upregulation of enzymes involved in generating ROS, such as NADPH oxidase, xanthine oxidase, and amine oxidases. The expression of genes involved in ascorbate and glutathione metabolism is also affected under this condition. ROS accumulation contributes to the degradation of monogalactosyl diacylglycerol (MGDG) and thylakoid membrane remodeling, leading to chlorosis. Quenching ROS under nitrogen limitation reduces the degradation of MGDG and the accumulation of TAG. This work shows that ROS accumulation, membrane remodeling, and TAG accumulation under nitrogen limitation are intricately linked in the microalga C. sorokiniana.

Evolutionary and immune-activating character analyses of NLR genes in algae suggest the ancient origin of plant intracellular immune receptors.

Nucleotide-binding leucine-rich repeat (NLR) proteins are crucial intracellular immune receptors in plants, responsible for detecting invading pathogens and initiating defense responses. While previous studies on the evolution and function of NLR genes were mainly limited to land plants, the evolutionary trajectory and immune-activating character of NLR genes in algae remain less explored. In this study, genome-wide NLR gene analysis was conducted on 44 chlorophyte species across seven classes and seven charophyte species across five classes. A few but variable number of NLR genes, ranging from one to 20, were identified in five chlorophytes and three charophytes, whereas no NLR gene was identified from the remaining algal genomes. Compared with land plants, algal genomes possess fewer or usually no NLR genes, implying that the expansion of NLR genes in land plants can be attributed to their adaptation to the more complex terrestrial pathogen environments. Through phylogenetic analysis, domain composition analysis, and conserved motifs profiling of the NBS domain, we detected shared and lineage-specific features between NLR genes in algae and land plants, supporting the common origin and continuous evolution of green plant NLR genes. Immune-activation assays revealed that both TNL and RNL proteins from green algae can elicit hypersensitive responses in Nicotiana benthamiana, indicating the molecular basis for immune activation has emerged in the early evolutionary stage of different types of NLR proteins. In summary, the results from this study suggest that NLR proteins may have taken a role as intracellular immune receptors in the common ancestor of green plants.

New records of two rare species of green algae (Chlorophyta) from snowfields of the Subpolar Urals and the Western Sayan

New records of two rare species of green algae (Chlorophyta) from snowfields of the Subpolar Urals and the Western Sayan

Harnessing the Propulsive Force of Microalgae with Microtrap to Drive Micromachines.

Microorganisms possess remarkable locomotion abilities, making them potential candidates for micromachine propulsion. Here, the use of Chlamydomonas Reinhardtii (CR) is explored, a motile green alga, as a micromotor by harnessing its propulsive force with microtraps. The objectives include developing the microtrap structure, evaluating trapping efficiency, and investigating the movement dynamics of biohybrid micromachines driven by CR. Experimental analysis demonstrates that trap design significantly influences trapping efficiency, with a specific trap configuration (multi-ring structure with diameters of 7µm - 10µm - 13µm) showing the highest effectiveness. The micromachine empowered with two CRs facing the same direction exhibits complex, random-like motion with yaw, pitch, and roll movements, while the micromachine with four CRs in a circular position each facing the tangential direction of the circle demonstrates controlled rotational motion. These findings highlight the degree of freedom and movement potential of biohybrid micromachines.

Environmental fate of phenobarbital in water: Homogeneous and non-homogeneous environment

In aqueous environments, phenobarbital (PB) undergoes degradation mediated by hydroxyl radicals (HO·) and sulfate radicals (SO4·−). In this study, a theoretical approach was used to investigate the oxidation of phenobarbital triggered by HO·/SO4·− in different dissociated forms of PB at different pH values, as well as the adsorption mechanism of phenobarbital on the silica surface and the non-homogeneous reaction with HO·. Our study confirms three primary reaction models for PB degradation: radical addition, hydrogen abstraction, and single electron transfer reactions. Thermodynamic and kinetic calculations show that the reaction of PB with HO· is the main degradation pathway compared to the reaction of SO4−. At the C5 and C6 positions, HO·-addition and H-abstraction from H6 and H7 are competitive mechanisms. However, in non-homogeneous environments, HO·-addition at C5 becomes the dominant pathway. Our work identifies the primary products of these degradation reactions. At a temperature of 298 K, the total rate constants for the degradation reactions of HO· with PB neutral molecules and anions were determined to be 2.06 M−1 s−1 and 4.11 × 107 M−1 s−1, respectively. In a non-homogeneous reaction with HO·, the total rate constant is 4.47 × 1010 M−1 s−1. Despite degradation, the majority of these products retain their potential to impact aquatic organisms. In particular, compounds such as 5-ethyl-5-hydroxypyrimidine-2,4,6(1H,3H,5H)-trione, 5-(1-hydroxyethyl)-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trione, and 5-acetyl-5-phenylpyrimidine-2,4,6(1H,3H,5H)-trione have a greater toxic effect on green algae. The findings underscore the need for future research to consider the environmental implications and ecotoxicity of PB. Such consideration is crucial for a comprehensive understanding of the long-term environmental impact of pharmaceutical residues in aquatic ecosystems.

A comprehensive review of current progress in biofuel production using marine algae biomass

The world's fossil fuel resources are rapidly depleting as the global population grows and energy demands rise. Current fossil fuel supplies are insufficient to meet rising demand and are nearing depletion. Careless exploitation of fossil fuels increases greenhouse gas emissions, environmental pollution, and global warming, resulting in ecological imbalances and health risks. Consequently, contamination, rising temperatures, and high oil costs have fueled the search for renewable and alternative energy sources. This study seeks to explore renewable energy alternatives that are critical to meeting future global energy demands. Marine algae such as red algae, green algae, and brown algae are gaining popularity as economically viable and environmentally friendly sources of renewable biofuel. Several studies are currently underway to assess the ability of marine algae to produce a variety of bioproducts, including biofuels. Macroalgae, in particular, emerges as an ideal resource for biofuel production due to their lipid and carbohydrate content, coupled with low or absent lignin content. The article investigates the potential of marine algal species to promote biofuel production and discusses novel methods for improving biofuel yields. It also emphasizes the economic factors and challenges associated with sustainable biofuel production.

Utilizing codon degeneracy in the design of donor DNA for CRISPR/Cas9-mediated gene editing to streamline the screening process for single amino acid mutations.

Chlamydomonas reinhardtii, a unicellular green alga, has been widely used as a model organism for studies of algal, plant and ciliary biology. The generation of targeted amino acid mutations is often necessary, and this can be achieved using CRISPR/Cas9 induced homology-directed repair to install genomic modifications from exogenous donor DNA. Due to the low gene editing efficiency, the technical challenge lies in identifying the mutant cells. Direct sequencing is not practical, and pre-screening is required. Here, we report a strategy for generating and screening for amino acid point mutations using the CRISPR/Cas9 gene editing system. The strategy is based on designing donor DNA using codon degeneracy, which enables the design of specific primers to facilitate mutant screening by PCR. An in vitro assembled RNP complex, along with a dsDNA donor and an antibiotic resistance marker, was electroporated into wild-type cells, followed by PCR screening. To demonstrate this principle, we have generated the E102K mutation in centrin and the K40R mutation in α-tubulin. The editing efficiencies at the target sites for Centrin, TUA1, TUA2 were 4, 24 and 8% respectively, based on PCR screening. More than 80% of the mutants with the expected size of PCR products were precisely edited, as revealed by DNA sequencing. Subsequently, the precision-edited mutants were biochemically verified. The introduction of codon degeneracy did not affect the gene expression of centrin and α-tubulins. Thus, this approach can be used to facilitate the identification of point mutations, especially in genes with low editing rates.

Actin cytoskeletal regulation of ciliogenesis in development and disease.

Primary cilia are antenna-like sensory organelles that are evolutionarily conserved in nearly all modern eukaryotes, from the single-celled green alga, Chlamydomonas reinhardtii, to vertebrates and mammals. Cilia are microtubule-based cellular projections that have adapted to perform a broad range of species-specific functions, from cell motility to detection of light and the transduction of extracellular mechanical and chemical signals. These functions render cilia essential for organismal development and survival. The high conservation of cilia has allowed for discoveries in C. reinhardtii to inform our understanding of the basic biology of mammalian primary cilia, and to provide insight into the genetic etiology of ciliopathies. Over the last two decades, a growing number of studies has revealed that multiple aspects of ciliary homeostasis are regulated by the actin cytoskeleton, including centrosome migration and positioning, vesicle transport to the basal body, ectocytosis, and ciliary-mediated signaling. Here, we review actin regulation of ciliary homeostasis, and highlight conserved and divergent mechanisms in C. reinhardtii and mammalian cells. Further, we compare the disease manifestations of patients with ciliopathies to those with mutations in actin and actin-associated genes, and propose that primary cilia defects caused by genetic alteration of the actin cytoskeleton may underlie certain birth defects.

A rapid aureochrome opto-switch enables diatom acclimation to dynamic light

Diatoms often outnumber other eukaryotic algae in the oceans, especially in coastal environments characterized by frequent fluctuations in light intensity. The identities and operational mechanisms of regulatory factors governing diatom acclimation to high light stress remain largely elusive. Here, we identified the AUREO1c protein from the coastal diatom Phaeodactylum tricornutum as a crucial regulator of non-photochemical quenching (NPQ), a photoprotective mechanism that dissipates excess energy as heat. AUREO1c detects light stress using a light-oxygen-voltage (LOV) domain and directly activates the expression of target genes, including LI818 genes that encode NPQ effector proteins, via its bZIP DNA-binding domain. In comparison to a kinase-mediated pathway reported in the freshwater green alga Chlamydomonas reinhardtii, the AUREO1c pathway exhibits a faster response and enables accumulation of LI818 transcript and protein levels to comparable degrees between continuous high-light and fluctuating-light treatments. We propose that the AUREO1c-LI818 pathway contributes to the resilience of diatoms under dynamic light conditions.