Catalyzes the prenylation of para-hydroxybenzoate (PHB) with an all-trans polyprenyl group. Mediates the second step in the final reaction sequence of coenzyme Q (CoQ) biosynthesis, which is the condensation of the polyisoprenoid side chain with PHB, generating the first membrane-bound Q intermediate. Required for embryo development. 4-hydroxybenzoate + an all-trans-polyprenyl diphosphate = a 4-hydroxy-3-all-trans-polyprenylbenzoate + diphosphate Cofactor biosynthesis; ubiquinone biosynthesis. A number of isoforms are produced. According to EST sequences. Expressed in flowers. Arrest of embryo development at an early stage of zygotic embryogenesis. Belongs to the UbiA prenyltransferase family.