Amphiphilic layered double hydroxides enhance plant-mediated delivery of dsRNAs to phloem‑feeding planthoppers

Abstract

RNA interference (RNAi) is an emerging tool in crop protection by exogenous applications of double-stranded RNAs (dsRNAs) to silence the expression of essential pest genes. Nevertheless, topical delivery of dsRNAs to sap-sucking insects is a major challenge due to the insufficient infiltration and translocation to plant vascular. Foliar sprayed layered double hydroxide (LDH) showed insufficient translocation in plant vascular and the supplement of surfactants caused phytotoxicity to plant. Thus, in the present study, LDH was transformed from hydrophilic to amphiphilic by fatty acids modification to obtain a surfactant-like LDH (LDHS) with good leaf adhesion, translocation and excellent biocompatibility. LDHS was synthesized via a mild hydrothermal method using MgCl2, FeCl3 and palm oil as the precursors, resulting in LDH coated with long-chained carboxylates as hydrophobic tails. LDHS showed good binding affinity with dsRNA and high affinity to rice leaves. Once loaded with dsRNA, LDHS were shown to enhance the uptake of dsRNA to rice brown planthoppers (Nilaparvata lugens) through a direct spray. Moreover, in planta, dsRNA-LDHS exhibited translocation from rice leaves to vascular bundles and finally into the planthoppers, delivered 2.5-fold higher dsRNA and caused higher mortalities of planthoppers than hydrophilic LDH with adjuvants. Herein we generate and validate a platform that can deliver dsRNA through either direct sprays or sprayed living plant to brown planthoppers with high efficiency, low toxicity and adjuvant-free. Consequently, it is a green potential selection using amphiphilic LDHS agents instead of the conventional gene carriers to prepare biopesticide nanoparticles.