An Evolutionarily Conserved Phosphatidate Phosphatase Maintains Lipid Droplet Number and ER Morphology But Not Nuclear Morphology

Abstract

Phosphatidic acid phosphatases are involved in the biosynthesis of phospholipids and triacylglycerol, and also act as transcriptional regulators. Studies to ascertain its role in lipid metabolism and membrane biogenesis are restricted only to Opisthokonta and Archaeplastida. Herein, we report the role of phosphatidate phosphatase (PAH) in Tetrahymena thermophila, belonging to the distantly related Alveolata clade. We identified two PAH homologs in Tetrahymena, TtPAH1, and TtPAH2. TtPAH1 maintains lipid droplet number and ER morphology but does not regulate nuclear morphology in Tetrahymena. TtPAH1 rescued all the known defects in yeast PAH1 strain and is conserved functionally between Tetrahymena and yeast. The homologous gene derived from Trypanosoma also rescued the defects of yeast PAH1 strain. Our results indicate that PAH1, previously known to be conserved between Opisthokonts, is also present in a set of distant lineages. Thus, a phosphatase cascade is evolutionarily conserved and is functionally interchangeable across eukaryotic lineages.