Expression of P-type ATPases of marine green microalga Dunaliella maritima under hyperosmotic salt shock

Partial sequences of P-type ATPases were cloned from the marine microalgae Dunaliella maritima: two presumably H+-ATPases (DmHA1 and DmHA2) and two putative Ca2+-ATPases (DmCA1 and DmCA2). The functions of cloned proteins were estimated on the bases of their primary structure similarity with the proteins whose functions have been already characterized. The transcriptional response of cloned ATPase genes to a sharp increase in the NaCl concentration in the culture medium (from 100 to 500 mM) was investigated by quantitative RT-PCR. Hyperosmotic salt shock led to a significant increase in DmHA2 expression and to a slight increase in DmCA2 expression, while the expression of two other ATPases, DmHA1 and DmCA1, was repressed. The obtained data indicate that DmHA2 is involved in maintenance of ion homeostasis in D. maritima cells under hyperosmotic salt shock.