Molecular response of gall induction by aphid Schlechtendalia chinensis (Bell) attack on Rhus chinensis Mill

Horned gall is named after its shape of irregular diamond, and is induced by the fluid-feeding aphid Schlechtendalia chinensis (Bell) attacks on the leaflets that are located in the branchlets of Rhus chinensis Mill., which is enriched in gallotannin and can be widely used in medicine and the food industry. To explain the molecular mechanism of gall development, we performed transcriptome analysis by Illumina deep sequencing and digital gene expression of four tissues, including galls, leaves that grew on the same branch as the gall taken (GL), leaves from a branch without any gall (LW), and leaves from a tree without any gall (CL). Differentially expressed genes abundantly enriched in the biosynthesis of secondary metabolites, plant–aphid interactions, and plant hormone signal transduction were highly expressed in galls compared with GL and LW. Phytohormone signal transduction, dominated by IAA and ABA, coordinates primary and secondary metabolism and thus induces gall induction and development after attack by aphids. This study provides a theoretical basis for the genetic improvement and processing of gallnut resources.