Low-CO2-inducible bestrophins outside the pyrenoid sustain high photosynthetic efficacy in diatoms.

Anion transporters sustain a variety of physiological states in cells. Bestrophins (BSTs) belong to a Cl- and/or HCO3- transporter family conserved in bacteria, animals, algae, and plants. Recently, putative BSTs were found in the green alga Chlamydomonas reinhardtii, where they are upregulated under low CO2 (LC) conditions and play an essential role in the CO2-concentrating mechanism (CCM).

Pyrenoid proteomics reveals independent evolution of the CO-concentrating organelle in chlorarachniophytes.

Pyrenoids are microcompartments that are universally found in the photosynthetic plastids of various eukaryotic algae. They contain ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and play a pivotal role in facilitating CO assimilation via CO-concentrating mechanisms (CCMs). Recent investigations involving model algae have revealed that pyrenoid-associated proteins participate in pyrenoid biogenesis and CCMs.

Sperm-specific histone H1 in highly condensed sperm nucleus of Sargassum horneri.

Spermatogenesis is one of the most dramatic changes in cell differentiation. Remarkable chromatin condensation of the nucleus is observed in animal, plant, and algal sperm. Sperm nuclear basic proteins (SNBPs), such as protamine and sperm-specific histone, are involved in chromatin condensation of the sperm nucleus.

The baseless mutant links protein phosphatase 2A with basal cell identity in the brown alga Ectocarpus.

The first mitotic division of the initial cell is a key event in all multicellular organisms and is associated with the establishment of major developmental axes and cell fates. The brown alga Ectocarpus has a haploid-diploid life cycle that involves the development of two multicellular generations: the sporophyte and the gametophyte. Each generation deploys a distinct developmental programme autonomously from an initial cell, the first cell division of which sets up the future body pattern.

Assembly and synthesis of the extracellular matrix in brown algae.

In brown algae, the extracellular matrix (ECM) and its constitutive polymers play crucial roles in specialized functions, including algal growth and development. In this review we offer an integrative view of ECM construction in brown algae. We briefly report the chemical composition of its main constituents, and how these are interlinked in a structural model.

Ultrastructural Observation of Cytokinesis and Plasmodesmata Formation in Brown Algae.

Similar to land plant cells, brown algal cells possess plasmodesmata with minute cytoplasmic tunnels, which enable the direct connection between adjacent cells. Plasmodesmata are distributed depending on the association of their formation with cytokinesis. Primary plasmodesmata are formed during cytokinesis, while secondary plasmodesmata appear on the cell wall septum following cytokinesis.

Ultrastructural observations of mitochondrial morphology through the life cycle of the brown alga, Mutiomo cylindricus (Cutleriaceae, Tilopteridales).

Mitochondrial morphology varies according to development and the physiological conditions of the cell. Here, we performed electron tomography using serial sections to analyze the number, individual volume, and morphological complexity of mitochondria in the cells across two generations in the life cycle of the brown alga Mutimo cylindricus. This species shows a heteromorphic alternation of generations between the macroscopic gametophyte and the crustose sporophyte during its life cycle and displays anisogamous sexual reproduction.

Targeted CRISPR-Cas9-based gene knockouts in the model brown alga Ectocarpus.

Brown algae are an important group of multicellular eukaryotes, phylogenetically distinct from both the animal and land plant lineages. Ectocarpus has emerged as a model organism to study diverse aspects of brown algal biology, but this system currently lacks an effective reverse genetics methodology to analyse the functions of selected target genes. Here, we report that mutations at specific target sites are generated following the introduction of CRISPR-Cas9 ribonucleoproteins into Ectocarpus cells, using either biolistics or microinjection as the delivery method.

Changes in Cell Wall Structure During Rhizoid Formation of Silvetia babingtonii (Fucales, Phaeophyceae) Zygotes.

We examined the ultrastructure of the cell wall and immunolocalization of alginates using specific antibodies against M-rich alginates and MG blocks during rhizoid formation in fucoid zygotes, Silvetia babingtonii. The thallus region of 24-h-old zygotes had a cell wall made of three layers with different fiber distribution. In the 12-h-old zygotes, three layers in the thallus were observed before rhizoid formation, namely the inner, middle, and outer layers.

Cytoplasmic inheritance of mitochondria and chloroplasts in the anisogamous brown alga Mutimo cylindricus (Phaeophyceae).

Based on the morphology of gametes, sexual reproduction in brown algae is usually classified into three types: isogamy, anisogamy, and oogamy. In isogamy, chloroplasts and chloroplast DNA (chlDNA) in the sporophyte cells are inherited biparentally, while mitochondria (or mitochondrial DNA, mtDNA) is inherited maternally. In oogamy, chloroplasts and mitochondria are inherited maternally.

Organelle inheritance and genome architecture variation in isogamous brown algae.

Among the brown algal lineages, Ectocarpales species have isogamous fertilization in which male and female gametes are morphologically similar. In contrast, female gametes are much larger than male gametes in the oogamous species found in many other brown algal lineages. It has been reported that the plastids of isogamous species are biparentally inherited whereas the plastids of oogamous species are maternally inherited.

Unusual Patterns of Mitochondrial Inheritance in the Brown Alga Ectocarpus.

Most eukaryotes inherit their mitochondria from only one of their parents. When there are different sexes, it is almost always the maternal mitochondria that are transmitted. Indeed, maternal uniparental inheritance has been reported for the brown alga Ectocarpus but we show in this study that different strains of Ectocarpus can exhibit different patterns of inheritance: Ectocarpus siliculosus strains showed maternal uniparental inheritance, as expected, but crosses using different Ectocarpus species 7 strains exhibited either paternal uniparental inheritance or an unusual pattern of transmission where progeny inherited either maternal or paternal mitochondria, but not both.

Phylogeographic diversification and postglacial range dynamics shed light on the conservation of the kelp .

Studies of postglacial range shifts could enhance our understanding of seaweed species' responses to climate change and hence facilitate the conservation of natural resources. However, the distribution dynamics and phylogeographic diversification of the commercially and ecologically important kelp in the Northwest Pacific (NWP) are still poorly surveyed. In this study, we analyzed the evolutionary history of using two mitochondrial markers and 24 nuclear microsatellites.

DISTAG/TBCCd1 Is Required for Basal Cell Fate Determination in .

Brown algae are one of the most developmentally complex groups within the eukaryotes. As in many land plants and animals, their main body axis is established early in development, when the initial cell gives rise to two daughter cells that have apical and basal identities, equivalent to shoot and root identities in land plants, respectively. We show here that mutations in the () gene lead to loss of basal structures during both the gametophyte and the sporophyte generations.

Calcium Control of the Sign of Phototaxis in Brown Algal Gametes of Mutimo cylindricus.

Brown algal swarmers usually exhibit positive or negative phototaxis. Such behaviors influence the increasing or decreasing dispersal distance or colonization on the new substratum. We confirmed that the sign of phototaxis (negative or positive) in male gametes of Mutimo cylindricus was affected by extracellular Ca influx through Ca channels.

Phototaxis and chemotaxis of brown algal swarmers.

Brown algae exhibit three patterns of sexual reproduction: isogamy, anisogamy, and oogamy. Unicellular swarmers including gametes and zoospores bear two heterogenous flagella, an anterior flagellum with mastigonemes (fine tripartite hairs) and a posterior one. In seawater, these flagellates usually receive physico-chemical signals for finding partners and good habitats.

Intercellular translocation of molecules via plasmodesmata in the multiseriate filamentous brown alga, Halopteris congesta (Sphacelariales, Phaeophyceae).

Despite the high number of studies on the fine structure of brown algal cells, only limited information is available on the intercelluar transportation of molecules via plasmodesmata in brown algae. In this study, plasmodesmatal permeability of Halopteris congesta was examined by observing the translocation of microinjected fluorescent tracers of different molecular sizes. The tip region of H.

Branch regeneration induced by sever damage in the brown alga Dictyota dichotoma (dictyotales, phaeophyceae).

Tissue wounds are mainly caused by herbivory, which is a serious threat for macro-algae, and brown algae are known to regenerate branches or buds in response to wounding. In the present paper, we describe a branch regeneration system, induced by sever damage, in the brown alga Dictyota dichotoma. Segmentations of juvenile thalli induced branch regenerations unless explants possessed apical cells.

Thylakoid luminal θ-carbonic anhydrase critical for growth and photosynthesis in the marine diatom Phaeodactylum tricornutum.

The algal pyrenoid is a large plastid body, where the majority of the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) resides, and it is proposed to be the hub of the algal CO2-concentrating mechanism (CCM) and CO2 fixation. The thylakoid membrane is often in close proximity to or penetrates the pyrenoid itself, implying there is a functional cooperation between the pyrenoid and thylakoid. Here, GFP tagging and immunolocalization analyses revealed that a previously unidentified protein, Pt43233, is targeted to the lumen of the pyrenoid-penetrating thylakoid in the marine diatom Phaeodactylum tricornutum The recombinant Pt43233 produced in Escherichia coli cells had both carbonic anhydrase (CA) and esterase activities.

Chemotactic movement in sperm of the oogamous brown algae, Saccharina japonica and Fucus distichus.

In oogamous species of brown algae such as Saccharina japonica and Fucus distichus, the sperm possess an unusual long posterior flagellum, which oscillates actively and produces a propulsive force during swimming. In this study, we quantitatively analyzed the effect of chemotactic responses on sperm swimming and flagellar waveforms by high-speed video recordings. We found that the thigmotactic response to the chemo-attractant was not enhanced during chemotactic swimming and that the swimming velocity of sperm did not decrease.

Distribution of alginate and cellulose and regulatory role of calcium in the cell wall of the brown alga Ectocarpus siliculosus (Ectocarpales, Phaeophyceae).

This work investigated a correlation between the three-dimensional architecture and compound-components of the brown algal cell wall. Calcium greatly contributes to the cell wall integrity. Brown algae have a unique cell wall consisting of alginate, cellulose, and sulfated polysaccharides.

Spermatogenesis and auxospore structure in the multipolar centric diatom Hydrosera.

Spermatogenesis and auxospore development were studied in the freshwater centric diatom Hydrosera triquetra. Spermatogenesis was unusual, lacking depauperating cell divisions within the spermatogonangium. Instead, a series of mitoses occurred within an undivided cell to produce a multinucleate plasmodium with peripheral nuclei, which then underwent meiosis.