A <i>trans</i>-long-chain prenyl diphosphate synthase promotes ubiquinone 10 biosynthesis in grape

Prenyl diphosphate synthase (PDS) plays indispensable roles in terpene biosynthesis. However, there is an ongoing debate regarding whether grape (Vitis vinifera) geranyl diphosphate synthase (VvGDS, VIT_15s0024g00850) can generate geranyl diphosphate (GPP), the precursor of monoterpene biosynthesis. Here, we demonstrated that VvGDS localizes in mitochondria and is an authentic trans-long-chain PDS (thus, VvGDS was renamed VvPDS), which is essential for ubiquinone (UQ) biosynthesis. This finding is in contrast to the initial association of VvPDS with GDS activity related to monoterpene biosynthesis. VvPDS not only falls within the subgroup comprising mitochondrial trans-long-chain PDSs, which participate in UQ biosynthesis in other eukaryotes, but also exhibits a positive association with UQ10 content in different grape tissues. VvPDS cannot catalyze GPP biosynthesis using isopentenyl diphosphate and dimethylallyl diphosphate as substrates. Furthermore, VvPDS functionally complements the yeast coq1 mutation lacking mitochondrial hexaprenyl diphosphate synthase activity and catalyzes UQ10 and UQ9 biosynthesis. Transient overexpression of VvPDS in grape leaves increased UQ10 accumulation, whereas silencing VvPDS caused an obvious reduction in UQ10 content. Similarly, the stable overexpression of VvPDS enhanced UQ10 accumulation in tobacco (Nicotiana tabacum), and these UQ10-overproducing plants exhibited improved oxidative stress tolerance, primarily through enhanced reactive oxygen species-scavenging capacity. Taken together, these findings provide biochemical and genetic evidence supporting UQ biosynthesis in grape and encourage future research to reevaluate the enzymatic functions and physiological roles of angiosperm PDSs.