Ab-GALFA, A bioassay for insect gall formation using the model plant Arabidopsis thaliana

Insect galls are abnormal plant organs formed by gall-inducing insects to provide shelter and nutrients for themselves. Although insect galls are spatialized complex structures with unique shapes and functions, the molecular mechanism of the gall formation and the screening system for the gall inducing effectors remains unknown. Here, we demonstrate that an extract of a gall-inducing aphid, Schlechtendalia chinensis, induces an abnormal structure in the root-tip region of Arabidopsis seedlings. The abnormal structure is composed of stem-like cells, vascular, and protective tissues, as observed in typical insect galls. Furthermore, we confirm similarities in the gene expression profiles between the aphid-treated seedlings and the early developmental stages of Rhus javanica galls formed by S. chinensis. Based on the results, we propose a model system for analyzing the molecular mechanisms of gall formation: the Arabidopsis-based Gall-Forming Assay (Ab-GALFA). Ab-GALFA could be used not only as a model to elucidate the mechanisms underlying gall formation, but also as a bioassay system to isolate insect effector molecules of gall-induction.

Automated summary

Insect galls are abnormal plant organs formed by gall-inducing insects to provide shelter and nutrients for themselves, but the molecular mechanism of gall formation and the screening system for gall-inducing effectors are still unknown. In this study, an extract from the gall-inducing aphid Schlechtendalia chinensis was found to induce an abnormal structure in the root-tip region of Arabidopsis seedlings, similar to typical insect galls. Furthermore, gene expression profiles between the aphid-treated seedlings and Rhus javanica galls formed by S. chinensis showed similarities. A model system called Arabidopsis-based Gall-Forming Assay (Ab-GALFA) is proposed to analyze the molecular mechanisms of gall formation and isolate insect effector molecules of gall-induction.