JPR Advance Access published online on January 19, 2007
Journal of Plankton Research, doi:10.1093/plankt/fbm011
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Presence of the distinct systems responsible for superoxide anion and hydrogen peroxide generation in red tide phytoplankton Chattonella marina and Chattonella ovata
a Division of Biochemistry, Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, Japan b Nagasaki Prefecture Collaboration of Regional Entities for the Advancement of Technological Excellence, JST, 2-1308-8 Ikeda Omura-city, Nagasaki, 856-0026, Japan c National Research Institute of Fisheries and Environment of Inland Sea, Maruishi, Ohno, Saeki, Hiroshima 739-0452, Japan d Sunny Health Co., Ltd. Yaesu Center Bldg. 1-6-6 Yaesu Chuo-ku, Tokyo, Japan 103-0028, Japan
* CORRESPONDING AUTHOR: t-oda{at}net.nagasaki-u.ac.jp
Received on August 24, 2006; revised on November 15, 2006; accepted on January 8, 2007
 |
Abstract |
|---|
Raphidophycean flagellates, Chattonella marina and Chattonella ovata, are harmful red tide phytoplankters; blooms of these phytoplankters often cause severe damage to fish farming. Previous studies have demonstrated that C. marina and C. ovata continuously produce reactive oxygen species (ROS) such as superoxide anion (O2–) hydrogen peroxide (H2O2) under normal growth conditions, and a ROS-mediated toxic mechanism against fish and other marine organisms has been proposed. Although the exact mechanism of ROS generation in these phytoplankters still remains to be clarified, our previous study suggested that NADPH oxidase-like enzyme located on the cell surface of C. marina may be involved in superoxide anion (O2–) generation. To investigate the localization of O2– and H2O2 generation in C. marina and C. ovata, we employed 2-methyl-6(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (MCLA) and 5-(and-6)-carboxy-2',7'-dichlorodihydrodihydrofluorescein dictate, acetyl ester (CM-H2DCFDA), which are specific fluorescent probe for detecting O2– and H2O2, respectively. Observation by fluorescence microscopy of live phytoplankters incubated with each probe revealed that O2– is mainly generated on the cell surface, while H2O2 is generated in the intracellular compartment in these phytoplankters. When the cells were ruptured by ultrasonic treatment, O2– levels of C. marina and C. ovata decreased significantly, whereas a few times higher levels of H2O2 were detected in the ruptured cell suspensions as compared to the levels of the live cell suspension. In immunoblotting analysis, the protein recognized by anti-human gp91 phox was detected in both species. These results suggest that, in both phytoplankters, underlying mechanisms of O2– and H2O2 generation may be distinct, and such systems are independently operating in the cells.
Key Words: Red tide phytoplankter • Harmful algal bloom • Reactive oxygen species (ROS) • Chattonella marina • Chattonella ovata