Resistance of A rabidopsis thaliana to the green peach aphid, M yzus persicae , involves camalexin and is regulated by micro RNA s

Small RNA s play important roles in resistance to plant viruses and the complex responses against pathogens and leaf‐chewing insects. We investigated whether small RNA pathways are involved in A rabidopsis resistance against a phloem‐feeding insect, the green peach aphid ( M yzus persicae ). We used a 2‐wk fecundity assay to assess aphid performance on A rabidopsis RNA silencing and defence pathway mutants. Quantitative real‐time polymerase chain reaction was used to monitor the transcriptional activity of defence‐related genes in plants of varying aphid susceptibility. High‐performance liquid chromatography‐mass spectrometry was employed to measure the accumulation of the antimicrobial compound camalexin. Artificial diet assays allowed the assessment of the effect of camalexin on aphid performance. M yzus persicae produces significantly less progeny on A rabidopsis micro RNA (mi RNA ) pathway mutants. Plants unable to process mi RNA s respond to aphid infestation with increased induction of PHYTOALEXIN DEFICIENT3 ( PAD 3 ) and production of camalexin. Aphids ingest camalexin when feeding on A rabidopsis and are more successful on pad3 and cyp79b2 / cyp79b3 mutants defective in camalexin production. Aphids produce less progeny on artificial diets containing camalexin. Our data indicate that camalexin functions beyond antimicrobial defence to also include hemipteran insects. This work also highlights the extensive role of the mi RNA ‐mediated regulation of secondary metabolic defence pathways with relevance to resistance against a hemipteran pest.