Nanoparticle-mediated delivery of RNA interference for prolonged virus protection in plants

N Mitter1, EA Worrall1, KE Robinson1, P Li2, RG Jain1, C Taochy1,3, S Fletcher1,3, BJ Carroll3 and ZP Xu2

  1. Queensland Alliance of Agriculture and Food Innovation, The University of Queensland,Brisbane, Queensland 4072, Australia
  2. Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Queensland 4072, Australia
  3. School of Chemistry & Molecular Biosciences,The University of Queensland, Brisbane, Queensland 4072, Australia

Plant pests and pathogens result in yield losses of 20-40% and are a major constraint on global food security. Current approaches to management of pests and diseases rely on plant resistance genes or transgenes, coupled with toxic chemical sprays. RNAi has emerged as a powerful strategy to engineer transgenic disease resistance in plants, but is limited due to community concern about genetically modified (GM) crops. Topical application of double-stranded (ds) RNA is an appealing alternative to GM crops for control of viruses. However, a major limitation in the topical application of dsRNA is a short protection window of 5-7 days post spraying. In this context, we have investigated the use of sheet-like positively charged layered double hydroxide (LDH) clay nanosheets as a dsRNA carrier for prolonged and effective protection against plant viruses. We have demonstrated that LDH nanosheets can load dsRNA to form dsRNA:LDH complexes referred to as BioClay. The dsRNA in BioClay is protected from nuclease activity, and can be detected on the leaf surface even 30 days after topical application. BioClay facilitates degradation of LDH nanosheets and sustained release of dsRNA on the leaf surface. Most importantly, we have shown that topical application of BioClay provides RNAi-based systemic protection against targeted viruses, not only on sprayed leaves, but also on newly emerged unsprayed leaves.