PHO4 transcription factor regulates triacylglycerol metabolism under low-phosphate conditions in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, PHM8 encodes a
phosphatase that catalyses the dephosphorylation
of lysophosphatidic acids to monoacylglycerol
and nucleotide monophosphate to nucleoside and
releases free phosphate. In this report, we investigated
the role of PHM8 in triacylglycerol metabolism
and its transcriptional regulation by a phosphate
responsive transcription factor Pho4p under lowphosphate
conditions. We found that the wild-type
(BY4741) cells accumulate triacylglycerol and the
expression of PHM8 was high under low-phosphate
conditions. Overexpression of PHM8 in the wildtype,
phm8Δ and quadruple phosphatase mutant
(pah1Δdpp1Δlpp1Δapp1Δ) caused an increase in the
triacylglycerol levels. However, the introduction of
the PHM8 deletion into the quadruple phosphatase
mutant resulted in a reduction in triacylglycerol
levels and LPA phosphatase activity. The transcriptional
activator Pho4p binds to the PHM8 promoter
under low-phosphate conditions, activating PHM8
expression, which leads to the formation of monoacylglycerol
from LPA. The synthesized monoacylglycerol
is acylated to diacylglycerol by Dga1p, which
is further acylated to triacylglycerol by the same
enzyme.