Plant-Generated Artificial Small RNAs Mediated Aphid Resistance

<div><p>Background</p><p>RNA silencing is an important mechanism for regulation of endogenous gene expression and defense against genomic intruders in plants. This natural defense system was adopted to generate virus-resistant plants even before the mechanism of RNA silencing was unveiled. With the clarification of that mechanism, transgenic antiviral plants were developed that expressed artificial virus-specific hairpin RNAs (hpRNAs) or microRNAs (amiRNAs) in host plants. Previous works also showed that plant-mediated RNA silencing technology could be a practical method for constructing insect-resistant plants by expressing hpRNAs targeting essential genes of insects.</p><p>Methodology/Principal findings</p><p>In this study, we chose aphid <i>Myzus persicae</i> of order Hemiptera as a target insect. To screen for aphid genes vulnerable to attack by plant-mediated RNA silencing to establish plant aphid resistance, we selected nine genes of <i>M. persicae</i> as silencing targets, and constructed their hpRNA-expressing vectors. For the acetylcholinesterase 2 coding gene (<i>MpAChE2</i>), two amiRNA-expressing vectors were also constructed. The vectors were transformed into tobacco plants (<i>Nicotiana tabacum</i> cv. Xanti). Insect challenge assays showed that most of the transgenic plants gained aphid resistance, among which those expressing hpRNAs targeting V-type proton ATPase subunit E-like (V-ATPaseE) or tubulin folding cofactor D (TBCD) genes displayed stronger aphicidal activity. The transgenic plants expressing amiRNAs targeting two different sites in the <i>MpAChE2</i> gene exhibited better aphid resistance than the plants expressing <i>MpAChE2</i>-specific hpRNA.</p><p>Conclusions/Significance</p><p>Our results indicated that plant-mediated insect-RNA silencing might be an effective way to develop plants resistant to insects with piercing-sucking mouthparts, and both the selection of vulnerable target genes and the biogenetic type of the small RNAs were crucial for the effectiveness of aphid control. The expression of insect-specific amiRNA is a promising and preferable approach to engineer plants resistant to aphids and, possibly, to other plant-infesting insects.</p>