IN-SITU HYBRIDIZATION ANALYSES OF NA, K-ATPASE ALPHA-SUBUNIT EXPRESSION DURING EARLY LARVAL DEVELOPMENT OF ARTEMIA-FRANCISCANA

The spatial pattern of expression of the mRNA encoded by the Na,K-ATPa se alpha-subunit cDNA clone pArATNa136 was determined by in situ hybri dization of first, second, and third instar Artemia franciscana larvae . This mRNA was expressed at high levels in the salt gland, the antenn al gland, and the end of the midgut, which are the three main osmoregu latory organs in Artemia at these stages of development. The pattern o f expression was similar at the three stages of development analyzed, although the level of expression increased during development, especia lly in the salt and antennal glands. The expression of the mRNA coding for another Na, K-ATPase alpha-subunit isoform, the proposed alpha 2- isoform, was also determined and was shown to be limited to the salt g land, These results suggest that the clone pArATNa136 codes for the bi ochemicaly defined alpha 1-isoform of the Na,K-ATPase alpha-subunit an d reinforce the importance of this isoform in osmoregulation at the th ree larval stages studied. The alpha 2-isoform may also be involved in osmoregulation during the first stages of larval development.