Two isoforms of sarco/endoplasmic reticulum calcium ATPase (SERCA) are essential in Caenorhabditis elegans

SERCA (Sarco/Endoplasmic Reticulum Calcium ATPase), a membrane bound Ca2+-/Mg2+- dependent ATPase that sequesters Ca2+ into the SR/ER lumen, is one of the essential components for the maintenance of intracellular Ca2+ homeostasis. Here we describe the identification and functional characterization of a C. elegans SERCA gene (ser-1). ser-l is a single gene alternatively spliced at its carboxyl terminus to form two isoforms (SER-1A and SER-1B) and displays a high homology (70% identity, 80% similarity) with mammalian SERCAs. Green fluorescent protein (GFP) and whole-mount immunostaining analyses reveal that SER-1 expresses in neuronal cells, body wall muscles, pharyngeal and vulval muscles, excretory cells, and vulva epithelial cells. Furthermore, SER-1::GFP expresses during embryonic stages and the expression is maintained through the adult stages. Double-stranded RNA injection (also known as RNAi) targeted to each SER-I isoform results in severe phenotypic defects: ser-IA(RNAi) animals show embryonic lethality, whereas ser-IB(RNAi) results in L1 larval arrest phenotype. These findings suggest that both isoforms of C. elegans SERCA, like in mammals, are essential for embryonic development and post-embryonic growth and survival. (C) 2000 Elsevier Science B.V. All rights reserved.