Gene expression profiling of Cacopsylla pyricola (Hemiptera: Psyllidae) infected with Ca. Phytoplasma pyri (Acholeplasmatales: Acholeplasmataceae) reveals candidate effectors and mechanisms of infection.

This article focuses on the molecular genetic interactions between the pear psylla (Cacopsylla pyricola) and the phytoplasma "Candidatus Phytoplasma pyri," the bacterial pathogen causing pear decline and peach yellow leafroll diseases. Using RNA sequencing and transcriptomic analysis, the study identified 126 differentially expressed genes in infected versus uninfected psylla, including 30 insect genes related to immunity, cytoskeletal function, and insecticide resistance, as well as candidate effector proteins from both the insect vector and the phytoplasma. Two distinct strains of Ca. Phytoplasma pyri, associated with pear decline (PD) and peach yellow leafroll (PYLR), were detected in psylla populations from the Pacific Northwest, with PYLR being more prevalent. The findings provide a foundational genetic resource for understanding host–pathogen interactions in this pathosystem and suggest potential targets for integrated pest and disease management strategies.