Persistence and transgenerational effect of plant-mediated RNAi in aphids.

A D Coleman,S A Hogenhout,S T Mugford,R H M Wouters

doi:10.1093/jxb/eru450

Abstract

Plant-mediated RNA interference (RNAi) has been successfully used as a tool to study gene function in aphids. The persistence and transgenerational effects of plant-mediated RNAi in the green peach aphid (GPA) Myzus persicae were investigated, with a focus on three genes with different functions in the aphid. Rack1 is a key component of various cellular processes inside aphids, while candidate effector genes MpC002 and MpPIntO2 (Mp2) modulate aphid-plant interactions. The gene sequences and functions did not affect RNAi-mediated down-regulation and persistence levels in the aphids. Maximal reduction of gene expression was ~70% and this was achieved at between 4 d and 8 d of exposure of the aphids to double-stranded RNA (dsRNA)-producing transgenic Arabidopsis thaliana. Moreover, gene expression levels returned to wild-type levels within ~6 d after removal of the aphids from the transgenic plants, indicating that a continuous supply of dsRNA is required to maintain the RNAi effect. Target genes were also down-regulated in nymphs born from mothers exposed to dsRNA-producing transgenic plants, and the RNAi effect lasted twice as long (12-14 d) in these nymphs. Investigations of the impact of RNAi over three generations of aphids revealed that aphids reared on dsMpC002 transgenic plants experienced a 60% decline in aphid reproduction levels compared with a 40% decline of aphids reared on dsRack1 and dsMpPIntO2 plants. In a field setting, a reduction of the aphid reproduction by 40-60% would dramatically decrease aphid population growth, contributing to a substantial reduction in agricultural losses.

Highlights

RNA interference (RNAi) is a cellular process used by animals, plants, and fungi as a means of post-transcriptional gene regulation to maintain normal growth and development, and mediates defence responses against viruses or transposable elements (Hannon, 2002)
Gene expression levels returned to wild-type levels within ~6 d after removal of the aphids from the transgenic plants, indicating that a continuous supply of double-stranded RNA (dsRNA) is required to maintain the RNAi effect
Because the first-generation females were transferred to non-transgenic Arabidopsis plants, the second-generation females were born on the non-transgenic plants and were not exposed to the dsRNA source via the plant host

Summary

Introduction

RNA interference (RNAi) is a cellular process used by animals, plants, and fungi as a means of post-transcriptional gene regulation to maintain normal growth and development, and mediates defence responses against viruses or transposable elements (Hannon, 2002). Over the past 15 years, RNAi has been successfully exploited as a reverse-genetics tool to study gene function in various organisms. The green peach aphid (GPA) Myzus persicae is an important agricultural pest and is developing into a valuable model system to investigate aphid gene function using RNAi-based techniques. Vast amounts of genomics data are being generated for aphid systems, increasing the usefulness of RNAi approaches. The pea aphid (Acyrthosiphon pisum) genome has been published (Richards et al, 2010), and GPA clone O and G006 are being sequenced as a collaboration between UK, French, and US research teams Functional genomics tools, such as RNAi, are essential to make use of the increasing availability of aphid genome and transcriptome sequence data

Methods

Results

Conclusion