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Abstract:
Background: Plant-mediated RNAi (PMRi) silencing of insect genes has enormous potential for crop protection, but
whether it works robustly under field conditions, particularly with lepidopteran pests, remains controversial. Wild
tobacco Nicotiana attenuata and cultivated tobacco (N. tabacum) (Solanaceae) is attacked by two closely related
specialist herbivores Manduca sexta and M. quinquemaculata (Lepidoptera, Sphingidae). When M. sexta larvae attack
transgenic N. attenuata plants expressing double-stranded RNA(dsRNA) targeting M. sexta’s midgut-expressed genes,
the nicotine-ingestion induced cytochrome P450 monooxygenase (invert repeat (ir)CYP6B46-plants) and the
lyciumoside-IV-ingestion induced β-glucosidase1 (irBG1-plants), these larval genes which are important for the
larvae’s response to ingested host toxins, are strongly silenced.
Results: Here we show that the PMRi procedure also silences the homologous genes in native M. quinquemaculata
larvae feeding on irCYP6B46 and irBG1-transgenic N. attenuata plants in nature. The PMRi lines shared 98 and 96%
sequence similarity with M. quinquemaculata homologous coding sequences, and CYP6B46 and BG1 transcripts were
reduced by ca. 90 and 80%, without reducing the transcripts of the larvae’s most similar, potential off-target genes.
Conclusions: We conclude that the PMRi procedure can robustly and specifically silence genes in native congeneric
insects that share sufficient sequence similarity and with the careful selection of targets, might protect crops from
attack by congeneric-groups of insect pests.
