Search

Brown algae are a group of multicellular, heterokont algae that have convergently evolved developmental complexity that rivals that of embryophytes, animals or fungi. Early in development, brown algal zygotes establish a basal and an apical pole, which will become respectively the basal system (holdfast) and the apical system (thallus) of the adult alga. Brown algae are interesting models for understanding the establishment of cell polarity in a broad evolutionary context, because they exhibit a large diversity of life cycles, reproductive strategies and, importantly, their zygotes are produced in large quantities free of parental tissue, with symmetry breaking and asymmetric division taking place in a highly synchronous manner. This review describes the current knowledge about the establishment of the apical-basal axis in the model brown seaweeds Ectocarpus, Dictyota, Fucus and Saccharina, highlighting the advantages and specific interests of each system. Ectocarpus is a genetic model system that allows access to the molecular basis of early development and life-cycle control over apical-basal polarity. The oogamous brown alga Fucus, together with emerging comparative models Dictyota and Saccharina, emphasize the diversity of strategies of symmetry breaking in determining a cell polarity vector in brown algae. A comparison with symmetry-breaking mechanisms in land plants, animals and fungi, reveals that the one-step zygote polarisation of Fucus compares well to Saccharomyces budding and Arabidopsis stomata development, while the two-phased symmetry breaking in the Dictyota zygote compares to Schizosaccharomyces fission, the Caenorhabditis anterior-posterior zygote polarisation and Arabidopsis prolate pollen polarisation. The apical-basal patterning in Saccharina zygotes on the other hand, may be seen as analogous to that of land plants. Overall, brown algae have the potential to bring exciting new information on how a single cell gives rise to an entire complex body plan., Competing Interests: Competing interests statement The authors declare no competing interests., (Copyright © 2022. Published by Elsevier Ltd.)

Although a broad variety of classes of bioactive compounds have already been isolated from seaweeds of the genus Dictyota , most different species are still chemically and biologically unexplored. Dictyota species are well-known brown seaweeds belonging to the Dictyotaceae (Phaeophyta). The phytochemical composition within the genus Dictyota has recently received considerable interest, and a vast array of components, including diterpenes, sesquiterepenes, sterols, amino acids, as well as saturated and polyunsaturated fatty acids, have been characterized. The contribution of these valued metabolites to the biological potential, which includes anti-proliferative, anti-microbial, antiviral, antioxidant, anti-inflammatory, and anti-hyperpigmentation activities, of the genus Dictyota has also been explored. Therefore, this is the most comprehensive review, focusing on the published literature relevant to the chemically and pharmacologically diverse biopharmaceuticals isolated from different species of the genus Dictyota during the period from 1976 to now.

Species of the brown algae of the genus Dictyota are rich sources of bioactive secondary metabolites with diverse structural features. Excellent progress has been made in the discovery of diterpenes possessing broad chemical defensive activities from this genus. Most of these diterpenes exhibit significant biological activities, such as antiviral, cytotoxic and chemical defensive activities. In the present review, we summarized diterpenes isolated from the brown algae of the genus., Competing Interests: The authors declare no conflict of interest.

The laminaran DdL and fucoidan DdF were obtained from the brown alga Dictyota dichotoma. DdF was a sulfated (28.9%) and acetylated heteropolysaccharide containing fucose, galactose, mannose and glucose (57.9, 20.4, 12.4 and 9.2mol%, respectively). DdL was a 1,3;1,6-β-d-glucan with the main chain built from 1,3-linked glucose residues and single glucose residue in branches at C6 (one branch on three glucose residues of the main chain). Sulfated (43.7%) laminaran DdLs was obtained from DdL by sulfation. It was determined that sulfates occur at C2, C4 and C6 of glucose residues. The anticancer effect of DdF, DdL, and DdLs (200μg/mL) was studied in vitro on colon cancer cells HCT-116, HT-29, and DLD-1. The effect of polysaccharides (40μg/mL) on colony formation of DLD-1 cancer cells after irradiation (4Gy) was investigated first. All polysaccharides showed a synergistic effect with X-ray irradiation against cancer cells, decreasing the amount and size of cancer cells colonies., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Previous studies have documented 836 species of marine macroalgae from Viet Nam. In the present study, marine algal samples were collected along the coast of south central Viet Nam. Morphological observations revealed three new records for the South China Sea, including Zellera tawallina and Grateloupia huangiae (Rhodophyta), and Dictyota grossedentata (Phaeophyceae). The results of morphological observations were supported by phylogenetic analyses. Therefore, the seaweed flora of Viet Nam now comprises 838 marine macroalgal species including 418 Rhodophyta, 149 Phaeophyceae, 183 Chlorophyta, and 88 Cyanobacteria. [ABSTRACT FROM AUTHOR]

Although a broad variety of classes of bioactive compounds have already been isolated from seaweeds of the genus Dictyota, most different species are still chemically and biologically unexplored. Dictyota species are well-known brown seaweeds belonging to the Dictyotaceae (Phaeophyta). The phytochemical composition within the genus Dictyota has recently received considerable interest, and a vast array of components, including diterpenes, sesquiterepenes, sterols, amino acids, as well as saturated and polyunsaturated fatty acids, have been characterized. The contribution of these valued metabolites to the biological potential, which includes anti-proliferative, anti-microbial, antiviral, antioxidant, anti-inflammatory, and anti-hyperpigmentation activities, of the genus Dictyota has also been explored. Therefore, this is the most comprehensive review, focusing on the published literature relevant to the chemically and pharmacologically diverse biopharmaceuticals isolated from different species of the genus Dictyota during the period from 1976 to now.

Due to the great genetic diversity of HIV, producing an effective vaccine is extremely difficult. The combined antiretroviral therapy, although not leading to a cure, is capable of preventing opportunistic infections, since it greatly reduces HIV viral load in the blood. Considering a large number of HIV infections occur through sexual intercourse, the use of topical microbicides could be very useful tools to reduce infection rates. Studies by our group showed that the dolabelladienetriol, isolated from the brown seaweed Dictyota friabilis, had a clear effect on replication by inhibiting HIV-1 replication in cell culture. In this study, we have demonstrated that pretreatment with this compound for 2 h or 1 to 5 days, showed an inhibitory effect ranging from 60 to 90 % in peripheral blood cells (PBMC) and macrophages infected with HIV-1, respectively. Following the studies, we found that the dolabelladienetriol after being subjected to the experimental model of ex vivo cervical mucosa did not show toxicities in concentrations that were used for the experiments. Subsequently, we evaluate the protective effect of dolabelladienetriol in explant model in uterine cervix, showing a curve of dose-dependent inhibition in treatment with different concentrations of the compound in the presence of HIV-1 with 20 to 99 % in concentrations of 0.15 and 14.4 μM, respectively. These studies demonstrate the important effect of dolabelladienetriol that can be recognized as a microbicide. [ABSTRACT FROM AUTHOR]

We studied development of the cytokinetic diaphragm (i.e., the membranous septum formed during cytokinesis) in vegetative cells of the brown algae Sphacelaria rigidula, Halopteris congesta and Dictyota dichotoma after cryofixation-freeze-substitution. Cytokinesis began by the gathering of organelles and large vesicles between daughter nuclei following telophase. Subsequently, a thin cytoplasmic strand was formed along this plane, where endoplasmic reticulum (ER), dictyosome vesicles and particular membranous elements, the flat cisternae, were accumulated. Their fusion formed a patchy diaphragm with irregular gaps. Fine tubular channels perforated the diaphragm during all stages of its formation. Following diaphragm completion, cell wall material was deposited in it. The new walls had ER-free plasmodesmata. In D. dichotoma, diaphragm development did not follow a definite pattern, i.e., centripetal or centrifugal, a phenomenon also confirmed in H. congesta. In contrast, in apical cells of S. rigidula the diaphragm started developing from the periphery, growing to some extent centripetally. In these cells, local cell wall deposition was greatest at the division site. In apical cells in which cytokinesis was experimentally inhibited a ring of wall material was usually deposited at the cytokinetic plane. [ABSTRACT FROM AUTHOR]

Abstract: Species of Dictyotales (brown algae) produce a large array of bioactive secondary metabolites possessing a broad defensive action against herbivores in the marine environment. This paper reviews the geographic and structural variations of the diterpenes found in Dictyotaceae species from the Tropical Atlantic American region. This analysis reveals that the geographical distribution of the Dictyotacean diterpenes parallels geographical and chemical differentiation, corroborating The Micromolecular Evolution Theory that states that invasion (=colonization) of new regions results in modification in the relative importance between the characteristic metabolic pathways of a given taxon. [Copyright &y& Elsevier]

Evaluates the ultrastructure of tetrasporogenesis in Dictyota dichotoma. Examination of the outgrowth of certain epidermal cells; Assessment of the large vacuoles and peripheral chloroplasts; Characteristic differentiation process of the stalk cells.