MgAl-layered double hydroxide nanoparticles mediated oral delivery of dsRNA silencing jhp and chi genes with sublethal effects in Phthorimaea absoluta

BACKGROUNDThe use of RNA interference (RNAi)-based technology for the management of agricultural insect pests is gaining momentum worldwide. A prerequisite for successful control by RNAi is the formulation of a highly efficient and stable double-stranded RNA (dsRNA). Here, we investigated the use of magnesium aluminum-layered double hydroxide (MgAl-LDH or LDH) nanoparticles complexed with dsRNA, termed BioClayTM, to target the juvenile hormone inducible protein (jhp) and the chitin synthase A (chi) genes of the South American tomato pinworm Phthorimaea (=Tuta) absoluta, a key pest of tomato crop. RESULTSDegradation assays showed that higher amounts of RNase A degraded dsRNA complexed with the LDH nanoparticles while lower RNase A amounts did not degrade the dsRNA. Furthermore, our findings revealed that dsRNA is stable after 60 min of incubation when in buffer solutions at pH 5 and pH 9, while naked dsRNA showed slight degradation at pH 11. Also, BioClayTM and naked dsRNAs targeting jhp and chi genes did not significantly increase larval mortality in P. absoluta, but induced sublethal phenotypes through reduced pupal weight and adult emergence. Gene expression analysis revealed significant reduction of 73% and 48% in transcript abundance of chi gene in larvae that fed on chi-dsRNA and BioClayTM chi-dsRNA after 72 h, respectively, while a 39% reduction in transcript of jhp gene was recorded only in larvae fed on BioClayTM jhp-dsRNA. CONCLUSIONOur findings provide critical insights into the significant impact of the use of dsRNA technology for targeted gene disruptions affecting important traits in P. absoluta and highlight the potential and opportunities that remain to be explored in the formulation and successful delivery of dsRNA-based active substances in pest management. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/683103v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@b4574forg.highwire.dtl.DTLVardef@1d0113borg.highwire.dtl.DTLVardef@11b5416org.highwire.dtl.DTLVardef@12da956_HPS_FORMAT_FIGEXP M_FIG C_FIG MgAl-LDH nanoparticles used as carrier to deliver dsRNA-based active substances hold potential to target jhp and chi candidate genes in Phthorimaea absoluta for the sustainable management of the pest.