EFFECTS OF VACUOLAR TRANSPORTER CHAPERONE 1 DISRUPTION ON PRODUCTION OF TRIACYLGLYCEROLS QUALITY AND QUANTITY IN CHLAMYDOMONAS REINHARDTII UNDER PHOSPHORUS DEPRIVATION

Microalgal lipid biosynthesis has been extensively studied under
nitrogen depleted conditions where triacylglycerols (TAGs) rapidly
accumulate while cell growth is arrested. However, less is known about
TAG production under phosphorus depleted conditions. Also, available
knowledge about polyphosphate metabolism in microalgae remains
limited. In this study, the molecular mechanisms of polyphosphate
biosynthesis and its link with the lipid biosynthesis pathway are
investigated in Chlamydomonas reinhardtii using a mutant defective in
the vacuolar transporter chaperone 1 gene (VTC1). The presence of
polyphosphate was abundant in the C. reinhardtii VTC1 rescue strain
when phosphorus was copious, whereas polyphosphate was degraded
when phosphorus was depleted in the medium. In addition, deletion of the
VTC1 gene enhanced TAGs production under phosphorus depleted
conditions, resulting in a 9.6-fold increase in TAGs concentration at day
21. A defect in the VTC1 gene also affected the fatty acid composition of
EFFECTS OF VACUOLAR TRANSPORTER CHAPERONE 1 DISRUPTION112
TAGs, promoting accumulation of mono- and poly-unsaturated fatty acids
at the expense of saturated fatty acids. These data suggest a negative
relationship between polyphosphate biosynthesis and TAG biosynthesis
in microalgae, and provide a new strategy to improve the quality and
yield of algal biofuels through manipulation of polyphosphate
biosynthesis.