Induced activity of pathogenesis related (PR) proteins in aphid galls

The favorable abiotic conditions within aphid galls may provide an optimal microhabitat for pathogenic microorganisms such as fungi and bacteria. Pathogens, especially fungi may be one of the main sources of mortality of the aphid gall-formers. We found high levels of pathogenesis related (PR) proteins in the tissue of galls induced by the aphids Smynthurodes betae (West.), Forda riccobonii (Stephani), and in particular Slavum wertheimae HRL (Homoptera: Pemphigidae: Fordinae) on Pistacia atlantica (Anacardiaceae). Compared with adjacent ungalled leaves, activity levels of chitinase and peroxidase, but not β-1,3-glucanase, were significantly higher in the galls. These PR proteins are an important component of the plant defense mechanisms against pathogens. The local induction of PR proteins in the galls suggests that manipulation of anti-microbial activity in the host tissue by gall-forming aphids may be self-benefiting.