Acts as a specific hypersensitive response (HR) elicitor. Has activity on tobacco (non-host plant) and petunia but is without activity on tomato (host plant); PopA3 seems to be more active than a PopA1-PopA2 mixture. Probably secreted via a type III secretion system (TTSS). PopA2 and PopA3 are produced from PopA1. Mass of PopA1. Mass of PopA3. Remains fully pathogenic on sensitive plants, suggesting the bacteria produces other pathogenicity factors.