Oral Presentation Science Protecting Plant Health 2017

Genome editing for Plant Defence (5019)

F Niam 1 , J Bally 1 , H Jung 1 , R P Hellens 1 , Peter M Waterhouse 1 2
  1. Centre for Tropical Crops and Biocommodities, QUT, Australia
  2. ARC Laureate Fellowship on Gene Harmony, QUT, Australia

A single lineage of Nicotiana benthamiana is widely used as a model plant and has been instrumental in making revolutionary discoveries about RNA interference (RNAi), viral defence and vaccine production. It is peerless in its susceptibility to viruses and in its amenability in transiently expressing transgene. We have been engineering the nuclear and chloroplast genomes of N.benthamiana by conventional breeding, RNAi, CRISPR and homologous recombination. Using these techniques and technologies we have conferred wide spectrum virus resistance, enhanced insect resistance, altered fatty acid metabolism and expressed sentinel reporter genes that measure recombination frequencies.

Trans-kingdom RNAi, which is based on making plants express double-stranded or hairpin (hp) RNA for ingestion by herbivorous pests. This RNA triggers silencing of specific genes within the pest leading to death or impaired growth. However, the efficacy of the approach appears to depend on the means of delivering the duplexed RNA. In our study, we introduced a hpRNA construct, targeting the acetylcholinesterase (ACE) gene of H. armigera, into the chloroplast genome of Nicotiana benthamiana. As the chloroplast, unlike the rest of the plant cell, lacks RNA interference machinery, the hpRNAs ingested from feeding on this plant are not pre-processed and are therefore more effective at triggering RNAi in the pest. Our transplastomic (chloroplast-transformed) lines, showed stronger protection against H. armigera herbivory than transgenic lines with hpRNA constructs integrated into the plant’s nuclear genome. These findings suggest that chloroplast expression of hpRNA is an attractive way of providing pest resistance in crops. The successes and challenges of these technologies will be discussed.