Abstract
Small RNAs 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 Arabidopsis resistance against a phloem-feeding insect, the green peach aphid (Myzus persicae).We used a 2-wk fecundity assay to assess aphid performance on Arabidopsis 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.Myzus persicae produces significantly less progeny on Arabidopsis microRNA (miRNA) pathway mutants. Plants unable to process miRNAs respond to aphid infestation with increased induction of PHYTOALEXIN DEFICIENT3 (PAD3) and production of camalexin. Aphids ingest camalexin when feeding on Arabidopsis 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 miRNA-mediated regulation of secondary metabolic defence pathways with relevance to resistance against a hemipteran pest.
Highlights
The green peach aphid (GPA), Myzus persicae, is one of the most destructive pests on cultivated crops worldwide (Blackman & Eastop, 2000)
Aphid fecundity is reduced on Arabidopsis miRNA mutants
To determine whether sRNAs are involved in Arabidopsis resistance to GPA, aphid performance was assessed on a collection of RNA-dependent RNA polymerase (RDR), DCL and AGO mutants and wild-type Col-0 Arabidopsis
Summary
The green peach aphid (GPA), Myzus persicae, is one of the most destructive pests on cultivated crops worldwide (Blackman & Eastop, 2000). GPA causes feeding damage and, more importantly, is the vector of many different plant viruses (Ng & Perry, 2004; Hogenhout et al, 2008). Insect herbivores, including aphids, have often specialized to colonize one or a few related plant species, whereas only a few herbivores, such as GPA, can colonize diverse plant species. Most plants can defend themselves effectively against the majority of insect herbivores. Insects are probably required to modulate a variety of plant processes to facilitate colonization. The mechanisms by which plants defend themselves against insect colonization and how aphids modulate plant processes are not fully understood
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