Fatty acid, phospholipid, and sphingolipid synthesis and the mevalonate pathway in C. elegans. (A) A schematic diagram shows the enzymes and substrates that are involved in processing acetyl-CoA (derived from glucose/mitochondrial citrate) to provide fatty acyl-CoA (red dashed box) for the phospholipid (magenta bracket) and sphingolipid (blue bracket) synthesis pathways. For reactions catalyzed by multiple enzymes with redundant functions (SMS-1, 2, 3, CGT-1, 2, 3, and PSSY-1, 2), the enzyme with expression in the AC as determined by AC-specific RNA-Seq was examined in the RNAi screen (Table S2, see Materials and methods). The enzymes whose RNAi mediated reduction led to a significant invasion defect are marked by asterisks (refer to Table S2). ACS, Acyl-CoA synthetase, represents 23 C. elegans homologs with predicted roles in Acyl-CoA synthesis; ACL, Acyl-CoA ligase, represents 14 C. elegans homologs with predicted activity as acyl-transferases; ATP, adenosine triphosphate; CTP, cytidine triphosphate; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PS, phosphatidylserine. (B) A schematic diagram showing the enzymes and substrates of the mevalonate pathway (green bracket) that promote Rab and CAAX geranylgeranylation, CAAX farnesylation, coenzyme Q synthesis, and protein glycosylation. The enzymes whose RNAi mediated depletion led to a significant invasion defect are marked by asterisks (refer to Table S2). COQ-1 and FDPS-1 in green dashed circle are the closest known homologs to the human geranylgeranyl diphosphate synthase. Schematics were adapted from Watts and Ristow (2017).