| Abstract: | A partial complementary DNA (cDNA) (DSA8) for a P-type ATPase was obtained from the halotolerant alga Dunaliella salina (Dunal) Teod. (Chlorophyceae). The cDNA exhibited greater than 90% homology to the cDNA for a H+-ATPase in D. bioculata Butcher. The expression of the gene that corresponded to DSA8 was decreased strongly by increases in NaCl concentration. The expression of a gene that corresponded to another ATPase (DSA1; possibly for a Ca2+-ATPase) from D. salina did not show the same decrease as did the DSA8. However, increased osmotic pressure due to glycerol resulted in the same decrease in the DSA8 gene. Under salt or osmotic stress, the activity of a H+-ATPase from microsomes of this alga also decreased. We suggest that expression of the gene for the plasma membrane H+-ATPase of D. salina is regulated by osmotic pressure rather than by the concentration of NaCl. |
