Abstract
We have reported the existence of Na-ATPase (Na-pump) on the plasma membrane of marine unicellular alga, Heterosigma akashiwo. We also reported the molecular cloning of the gene of Na-ATPase (HANA) from H. akashiwo. Recently, several studies have suggested the existence of homologue gene of HANA in alga. To investigate the function and mechanism of Na-ATPase in alga, we overexpressed HANA gene in yeast and higher plants. S. cerevisiae mutants lacking endogenous Na-ATPase or vacuolar protease were transformed HANA gene. Although transgenic yeasts express large amount of mRNA, neither of them could not express HANA protein constantly. We could detect few amount of HANA protein in transgenic Arabidopsis but break down of HANA protein seems also very quick. HANA expressing transgenic Arabidopsis showed Li ion tolerance feature compared with vector-transformed control.
