Isolation and Characterization of a Sex-Specific Lectin in a Marine Red Alga, Aglaothamnion oosumiense Itono

Abstract

In red algae, spermatial binding to female trichogynes is mediated by a lectin-carbohydrate complementary system. Aglaothamnion oosumiense is a microscopic filamentous red alga. The gamete recognition and binding occur at the surface of the hairlike trichogyne on the female carpogonium. Male spermatia are nonmotile. Previous studies suggested the presence of a lectin responsible for gamete recognition on the surface of female trychogynes. A novel N-acetyl-D-galactosamine-specific protein was isolated from female plants of A. oosumiense by affinity chromatography and named AOL1. The lectin was monomeric and did not agglutinate horse blood or human erythrocytes. The N-terminal amino acid sequence of the protein was analyzed, and degenerate primers were designed. A full-length cDNA encoding the lectin was obtained using rapid amplification of cDNA ends-PCR (RACE-PCR). The cDNA was 1,095 bp in length and coded for a protein of 259 amino acids with a deduced molecular mass of 21.4 kDa, which agreed well with the protein data. PCR analysis using genomic DNA showed that both male and female plants have this gene. However, Northern blotting and two-dimensional electrophoresis showed that this protein was expressed 12 to 15 times more in female plants. The lectin inhibited spermatial binding to the trichogynes when preincubated with spermatia, suggesting its involvement in gamete binding.T he precise point of gamete recognition varies along the continuum of reproduction and development, from directional movements that bring the compatible gametes together through many steps of fertilization to the formation of embryonic offspring. Fertilization in red algae, however, begins with direct contact between a male spermatium and a female trichogyne because both male and female gametes are nonmotile (7, 32). As spermatial binding to trichogynes is highly selective, some recognition factors are expected to be present along their surfaces (11,16,17,25). Cell surface glycoconjugates have been reported as important factors for cell-cell recognition in many organisms (24). Such recognition systems depend on complementary binding between carbohydrate moieties on one cell with specific sugar-binding lectins on another cell.Lectin-carbohydrate complementary systems have been reported in gamete recognition of marine algae for a long time (1, 8-10, 17, 22, 31), but most studies used indirect evidence from inhibition experiments using carbohydrates or foreign lectins (mostly from land plants) as blocking agents of gamete binding. Although several studies have reported on the isolation of marine algal lectins, the number of these proteins that have been purified and characterized is still small (4, 33).Our previous cytochemical study on the fertilization of Aglaothamnion oosumiense Itono suggested the presence of N-acetyl-Dgalactosamine (GalNAc) and/or D-methyl mannose-specific lectin(s) on the surface of female trichogynes (11). Here we report the purification and molecular characterization of a novel GalNAc-binding lectin from this spec...

Functional Recombinants Designed from a Fetuin/Asialofetuin-Specific Marine Algal Lectin, Rhodobindin

“…Diploid plants of A. callophyllidicola were collected from Ochungdo, western coast of Korea and maintained in IMR medium [ 13 ]. Plants were grown at 15 °C in 16:8 h light and dark cycles with >20 μmol photons m −2 ·s −1 light provided by cool-white fluorescent bulbs [ 12 ].…”

“…For the investigation of hemagglutinating activity we followed protocols described by Han et al [ 12 ]. Horse blood was purchased from HanilComed (HanilComed, Seongnam, Korea) and washed with PBS.…”

“…Lectin-carbohydrate complementary systems has been proposed for gamete-gamete recognition and binding in red algae [ 10 , 11 , 12 ]. Recently the female-specific lectin involved in this process has been isolated from Aglaothamnion callophyllidicola and named Rhodobindin [ 13 ].…”

Characterization of a Novel Mannose-Binding Lectin with Antiviral Activities from Red Alga, Grateloupia chiangii

“…Among the purified red algal lectins, few have had their pharmacological applications discussed or confirmed (i.e., Griffithsin) [19,20]. Although the role of lectins in red algae remains unclear, several roles have been suggested, including an involvement in spermatia and tricogyne mutual recognition in sexual reproduction [21,22].…”

Sex‐Specific Genes and their Expression in the Life History of the Red Alga Bostrychia moritziana (Ceramiales, Rhodomelaceae)

“…A sex‐specifically expressed lectin which is involved in gamete binding was isolated from this species (Han et al. 2012, Shim et al. 2012).…”