Lectins have the ability to bind specific carbohydrates and they have potential applications as medical and pharmacological agents. The unique structure and usefulness of red algal lectin have been reported, but these lectins are limited to a few marine algal groups. In this study, a novel mannose-binding lectin from Grateloupia chiangii (G. chiangii lectin, GCL) was purified using antiviral screens and affinity chromatography. We characterized the molecular weight, agglutination activity, hemagglutination activity, and heat stability of GCL. To determine the carbohydrate specificity, a glycan microarray was performed. GCL showed strong binding affinity for Maltohexaose-β-Sp1 and Maltoheptaose-β-Sp1 with weak affinity for other monosaccharides and preferred binding to high-mannan structures. The N-terminal sequence and peptide sequence of GCL were determined using an Edman degradation method and LC-MS/MS, and the cDNA and peptide sequences were deduced. GCL was shown to consist of 231 amino acids (24.9 kDa) and the N-terminus methionine was eliminated after translation. GCL possessed a tandem repeat structure of six domains, similar to the other red algal lectins. The mannose binding properties and tandem repeat structure of GCL may confer it the potential to act as an antiviral agent for protection against viral infection.

Dinoflagellates are an important group of phytoplanktons, characterized by two dissimilar flagella and distinctive features of both plants and animals. Dinoflagellate-generated harmful algal blooms (HABs) and associated damage frequently occur in coastal areas, which are concomitant with increasing eutrophication and climate change derived from anthropogenic waste and atmospheric carbon dioxide, respectively. The severe damage and harmful effects of dinoflagellate phycotoxins in the fishing industry have been recognized over the past few decades, and the management and monitoring of HABs have attracted much attention, leaving aside the industrial application of their valuable toxins. Specific modes of action of the organisms’ toxins can effectively be utilized for producing beneficial materials, such as Botox and other therapeutic agents. This review aims to explore the potential industrial applications of marine dinoflagellate phycotoxins; furthermore, this review focuses on their modes of action and summarizes the available knowledge on them.

The discovery of new highly effective anticancer drugs with few side effects is a challenge for drug development research. Natural or synthetic anticancer peptides (ACPs) represent a new generation of anticancer agents with high selectivity and specificity. The rapid emergence of chemoradiation-resistant lung cancer has necessitated the discovery of novel anticancer agents as alternatives to conventional therapeutics. In this study, we synthesized a peptide containing 22 amino acids and characterized it as a novel ACP (MP06) derived from green sea algae, Bryopsis plumosa. Using the ACP database, MP06 was predicted to possess an alpha-helical secondary structure and functionality. The anti-proliferative and apoptotic effects of the MP06, determined using the cytotoxicity assay and Annexin V/propidium iodide staining kit, were significantly higher in non-small-cell lung cancer (NSCLC) cells than in non-cancerous lung cells. We confirmed that MP06 suppressed cellular migration and invasion and inhibited the expression of N-cadherin and vimentin, the markers of epithelial–mesenchymal transition. Moreover, MP06 effectively reduced the metastasis of tumor xenografts in zebrafish embryos. In conclusion, we suggest considering MP06 as a novel candidate for the development of new anticancer drugs functioning via the ERK signaling pathway.

Lectin is a carbohydrate-binding protein that recognizes specific cells by binding to cell-surface polysaccharides. Tumor cells generally show various glycosylation patterns, making them distinguishable from non-cancerous cells. Consequently, lectin has been suggested as a good anticancer agent. Herein, the anticancer activity of Bryopsis plumosa lectins (BPL1, BPL2, and BPL3) was screened and tested against lung cancer cell lines (A549, H460, and H1299). BPL2 showed high anticancer activity compared to BPL1 and BPL3. Cell viability was dependent on BPL2 concentration and incubation time. The IC₅₀ value for lung cancer cells was 50 μg/mL after 24 h of incubation in BPL2 containing medium; however, BPL2 (50 μg/mL) showed weak toxicity in non-cancerous cells (MRC5). BPL2 affected cancer cell growth while non-cancerous cells were less affected. Further, BPL2 (20 μg/mL) inhibited cancer cell invasion and migration (rates were ˂20%). BPL2 induced the downregulation of epithelial-to-mesenchymal transition-related genes (Zeb1, vimentin, and Twist). Co-treatment with BPL2 and gefitinib (10 μg/mL and 10 μM, respectively) showed a synergistic effect compared with monotherapy. BPL2 or gefitinib monotherapy resulted in approximately 90% and 70% cell viability, respectively, with concomitant treatment showing 40% cell viability. Overall, BPL2 can be considered a good candidate for development into an anticancer agent.

The algal cell wall is a potent barrier for delivery of transgenes for genetic engineering. Conventional methods developed for higher plant systems are often unable to penetrate or remove algal cell walls owing to their unique physical and chemical properties. Therefore, we developed a simple transformation method for Chlamydomonas reinhardtii using commercially available enzymes. Out of 7 enzymes screened for cell wall disruption, a commercial form of subtilisin (Alcalase) was the most effective at a low concentration (0.3 Anson units/mL). The efficiency was comparable to that of gamete lytic enzyme, a protease commonly used for the genetic transformation of C. reinhardtii. The transformation efficiency of our noninvasive method was similar to that of previous methods using autolysin as a cell wall-degrading enzyme in conjunction with glass bead transformation. Subtilisin showed approximately 35% sequence identity with sporangin, a hatching enzyme of C. reinhardtii, and shared conserved active domains, which may explain the effective cell wall degradation. Our trans­formation method using commercial subtilisin is more reliable and time saving than the conventional method using autolysin released from gametes for cell wall lysis.

Lectin is an important protein in medical and pharmacological applications. Impurities in lectin derived from natural sources and the generation of inactive proteins by recombinant technology are major obstacles for the use of lectins. Expressing recombinant lectin with a tandem repeat structure can potentially overcome these problems, but few studies have systematically examined this possibility. This was investigated in the present study using three distinct forms of recombinant mannose-binding lectin from Bryopsis plumosa (BPL2)—i.e., the monomer (rD1BPL2), as well as the dimer (rD2BPL2), and tetramer (rD4BPL2) arranged as tandem repeats. The concentration of the inducer molecule isopropyl β-D-1-thiogalactopyranoside and the induction time had no effect on the efficiency of the expression of each construct. Of the tested constructs, only rD4BPL2 showed hemagglutination activity towards horse erythrocytes; the activity of towards the former was 64 times higher than that of native BPL2. Recombinant and native BPL2 showed differences in carbohydrate specificity; the activity of rD4BPL2 was inhibited by the glycoprotein fetuin, whereas that of native BPL2 was also inhibited by d-mannose. Our results indicate that expression as tandem repeat sequences can increase the efficiency of lectin production on a large scale using a bacterial expression system.