In Tzenkethi culture, Ap-Rej was a title which indicated an individual had been able to speak for the Autarch of the Tzenkethi Coalition. An Ap-Rej was essentially a mouthpiece for the Autarch, an order from an individual with this title carried the same weight as if it had been directly from the Autarch.
In 2385, the Tzenkethi Metiger stated she couldn't comply with a suggestion given by Katherine Pulaski, as it would have gone against an order given by an Ap-Rej. (DS9 novel: The Missing)
Mertikor was an Ap-Rej. (ST - Typhon Pact novel: Brinkmanship)