Inhibition of acetyl-CoA carboxylase renders phosphatidylcholine redundant in yeast

Phosphatidylcholine (PC) is a very abundant membrane lipid component in most eukaryotes including baker's yeast, serving a multitude of functions in addition to that of building block of the lipid bilayer. Here we show that PC is evolvable essential in yeast by isolating cho2opi3 suppressor mutants devoid of PC that exhibit robust growth. The requirement for PC is suppressed by 2n-1 aneuploidy with monosomy of chromosome XV, or by a point mutation in the ACC1 gene encoding acetyl-CoA carboxylase. Both genetic adaptations decrease Acc1 activity and thereby reduce average acyl chain length.