Characterization of Coq9 in the CoQ Biosynthetic Pathway.

Coenzyme Q, also known as ubiquinone, is a fat-soluble isoprene quinone that serves as a cofactor for numerous enzymes across all domains of life. However, the biosynthetic pathway for this important molecule in plants has been examined in only a limited number of studies. In yeast and mammals, Coq9, an isoprenoid-lipid-binding protein, is essential for CoQ biosynthesis. Previous studies showed that failed to complement the fission yeast null mutant, and its function in plants remains unknown. In this study, we demonstrated that expression of rescued the growth of a yeast temperature-sensitive mutant and increased CoQ content. Phylogenetic analysis revealed that Coq9 is widely present in green plants. Green fluorescent protein (GFP) fusion experiments showed that Coq9 is targeted to mitochondria. Disruption of the gene in results in lower amounts of CoQ. Our work suggests that plant Coq9 is required for efficient CoQ biosynthesis. These findings provide new insights into the evolution of CoQ biosynthesis in plants. The identification of Coq9 as a key player in CoQ biosynthesis in plants opens up new avenues for understanding the regulation of this important metabolic pathway.