Arabidopsis thaliana as a model plant for understanding phytoplasma interactions with plant and insect hosts

With increasingly strict restrictions being imposed upon the utilization of environmentally damaging pesticides, research must focus upon the development of phytoplasma-resistant crops as a strategy to control disease outbreak. An enhanced understanding of the mechanisms by which phytoplasmas infect their plant hosts will facilitate achieving this objective. In this study, we report that Aster Yellows phytoplasma strain Witches Broom (AY-WB; ‘Candidatus Phytoplasma asteris’) readily infects the model plant Arabidopsis thaliana as transmitted by the aster leafhopper Macrosteles quadrilineatus. Inoculated plants exhibit symptoms that are characteristic of infection with AY-WB, including witches broom, virescence, phyllody and increased leafhopper fecundity indicating that the AY-WB-Arabidopsis thaliana interaction represents an experimental pathosystem to enable research into phytoplasma virulence. Previously, 56 candidate effectors were identified by mining the fully sequenced AY-WB genome for genes encoding secreted proteins. Studying these effectors resulted in the identification of three AY-WB effectors that induce various phenotypes in A. thaliana, including phyllody and increased leafhopper fecundity. Thus, the model plant A. thaliana has allowed rapid progress with understanding how phytoplasma effectors alter plant development and plant-insect interactions.