THE EFFECT OF NaCl FOR SEVERAL ENZYMES IN A SEAGRASS, ZOSTERA MARINA

• Published in: Journal of Plant Research 2001, Vol.114 (suppl), p.65-66
• Main Authors: Yuki Muramatsu, Akiko Harada, Shingo Takagi, Toshiyuki Fukuhara
• Format: Article
• Language: Japanese
• ISSN: 0918-9440

A seagrass, Zostera marina, which is a monocot plant grows in the sea and has salt tolerance. We expected that the plasma membrane H+-ATPase must play an important role in the survival of seagrass in seawater. In plant cells, plasma membrane H+-ATPase generates a H+ electrochemical gradient and provides a driving force to transport various nutrients and ions across the plasma membrane. The plasma membrane fractions were prepared from Zostera marina, Vallisneria gigantea (a freshwater monocot) and Oryza sativa (rice) by an aqueous-polymer two-phase system. The vanadate-sensitive (plasma membrane) ATPase activities in Z. marina, V. gigantea and O. sativa fractions were assayed in the presence of NaCl at various concentrations. In V. gigantea and O. sativa fractions, the vanadate-sensitive ATPase activities were inhibited by addition of 510 mM NaCl. By contrast, in the Z. marina fraction, the activity was not inhibited. On the other hand, the nitrate-sensitive (tonoplast) and azide-sensitive (mitochondrial) ATFase activities in the crude microsomal fraction from Z. marina were inhibited by 510 mM NaCi. In Z. marina plasma membrane H+ ATPase, the optimal pH of ATPase activity was 6.0. Furthermore, after treatment of the plasma membrane fraction with trypsin, the ATPase activity was increased to 1.5 fold. These properties were similar to those of plasma membrane H+ ATPase of other higher plants. Seagrass may be able to live in the high salt environment by putting out excess Na+ actively across plasma membrane.