In the biosynthesis of phospholipids and triacylglycerol, glycerol phosphate is sequentially acylated at the sn -1 and sn -2 positions by acyltransferases, namely by glycerol-3-phosphate acyltransferase (GPAT) and lysophosphatidic acid acyltransferase (LPAAT). Both GPAT and LPAAT have been reported to contain highly conserved regions consisting of four repetitive blocks of the so-called acyltransferase motif. A human genome database search revealed 15 genes containing the acyltransferase motif, of which physiological functions and substrate specificities are largely unknown. In this study, we identified 14 genes containing the acyltransferase motif in C. elegans genome sequences (
acl-1 ~ 14 ), and focused on
acl-4 , which shows a significant homology with the corresponding human genes. To elucidate the physiological functions of
acl-4 , we isolated the deletion mutants by UV/TMP method. The
acl-4 (
qa3110) allele contains a premature stop mutation predicted to delete acyltransferase motif, suggesting that this allele is likely to eliminate gene function completely. The
acl-4 (
qa3110) grew normally and exhibited no apparent abnormal phenotype. Since acl genes encode the putative acyltransferases, which transfer fatty acyl chain to the lysophospholipid, we analyzed the
acl-4 (
qa3110) in fat mutant backgrounds in which fatty acid compositions are altered (Watts et al ., 2002 PNAS 99 , 5854-5859, Lesa et al ., 2003 J Cell Sci. 116 , 4965-4975). Interestingly, we found that
acl-4;
fat-3 double mutants, which are depleted of long chain polyunsaturated fatty acids(LC-PUFAs), showed severe movement abnormalities. These defects were rescued by application of exogenous LC-PUFAs. Next, we examined the expression pattern of
acl-4 . We generated transgenic worms expressing
acl-4p::GFP and found that
acl-4p::GFP was expressed in ventral nerve cord, some sensory neurons and muscles. We are currently trying to rescue the movement defects of the
acl-4;
fat-3 mutants by the tissue specific
fat-3 expression, and to examine the substrate specificity in vitro .