Properties of soft-coral lectins and their possible roles in symbiosis.

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09460096
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Fisheries chemistry
• Research Institution: Kitasato University
• Principal Investigator: KAMIYA Hisao School of Fisheries Sciences, Kitasato university, Professor, 水産学部, 教授 (80011964)
• Co-Investigator(Kenkyū-buntansha): KOIKE Kazuhiko School of Fisheries Sciences, Kitasato university, Assistant Professor, 水産学部, 助手 (30265722) ; JIMBO Mituru School of Fisheries Sciences, Kitasato University, Assistant Professor, 水産学部, 助手 (10291650) ; MURAMOTO Koji Faculty of Agriculture, Tohoku University, Professor, 農学部, 教授 (90157800)
• Project Period (FY): 1997 – 1998
• Keywords: lectin / soft-coral / Sinularia lochmodes / Symbiodinium / biomineralization / nematocyst / invertebrate

Research Abstract

Soft-coral specimen, which contain a D-galactose-binding lectin, was identified as Sin ularia lochmodes. The symbiont was found to belong to Symbioclinium sp. by its srDNA analysis. A major lectin named SLL was purified from S.lochmodes extract by affinity chromatography on HCl-treated Sepharose 4B and FPLC on a Superdex S-200 column. In FPLC, three protein peaks were obserbed and the most active hemagglutination was detected in the slowest-eluted peak. Although two other protein peaks were also active, these components were the minor components because of the low total activity of these fractions ; less than 2% of the total hemagglutinating activity. SDS-polyacrylamide gel electrophoresis revealed that SLL was composed of a single polypeptide having a molecular weight of 15600. SLL showed a resistance against the heating at 60* for 90 mm. When checked with rabbit erythrocytes, the hemagglutinating activity was unchanged with or without calcium ions. However, an enhanced activity was o bserved at the presence of calcium ions more than 10 mM in the medium when examined with horse eiythrocytes. The sequence of the amino-terminal region of SLL was Arg-Leu-Ile-His-Val-Ser--Arg-Cys-Glu-Met-Gly-. The inhibition of calcium carbonate crystal growth by SLL was observed at a concentration of 41mug/ml.
In immuno-histochemical examination on the materials ejected from S.lochmodes and on the sections prepared with S.lochmodes tissues by immunogold labelling using anti-SLL rabbit antibody, SLL was detected in the surrounding material of the Symbioclinium sp. cell wall, nematocysts, and risosome-Jike organs. The Symbiodinium cells were detected in the gastrodermal cells but not in the mesenchyme. The labelling were also observed in the mesenchyme, though the density was less than half compared to the gastrodermal cells. The trial for the Symbiodinium culture under various conditions was unsuccessful.
The results obtained suggest that the physiological role of S.lochmodes lectin play roles in the hourbaring the symbiotic microalgae as well as biomineralization. The possibility of the lectin production by the symbiotic algae was rule out because of the results obtained in the immunohistochemical study.