Ribosomal RNA-specific antisense DNA and double-stranded DNA trigger rRNA biogenesis and insecticidal effect on insect pest Coccus hesperidum

Invented in 2008, contact unmodified antisense DNA biotechnology (CUADb) is built on the use of short antisense DNA oligonucleotides (oligos) for insect pest control. Being a novel class of insecticides, oligonucleotide insecticides target pest rRNAs and/or pre-rRNAs and recently showed high insecticidal potential against sap-feeding insect pests, main vectors of plant DNA viruses and one of the most economically-damaging groups of herbivorous insects. In order to use all possible opportunities of CUADb, in this article insecticidal potential of short 11-mer antisense DNA oligos was investigated for Coccus hesperidum control in comparison with long 56-mer single-stranded and double-stranded DNA sequences and lower efficiency of the latter was found. At the end of the experiment, on the 9 th day, the highest mortality rate among antisense oligos was reached for Coccus-11 group (97.66 ± 4.04 %), while for long sequences the highest mortality rate was obtained for double-stranded DNA fragment in dsCoccus-56 group (77.09 ± 6.24 %). Also in this article architecture of DNA containment (DNAc) mechanism is described representing interesting and important for insect cell life interplay between rRNAs and different types of DNA oligos. During DNAc, Coccus-11 caused increased ribosome biogenesis and ATP production through metabolic switch in energy synthesis from carbohydrates to lipids but eventually caused ‘kinase disaster’ through downregulation of most kinases due to insufficient level of ATP produced. In the course of DNAc, hypercompensation of target rRNA is triggered by all highly and all somewhat complementary DNA oligos but more pronounced later degradation of target rRNA and significant insect pest mortality is seen only in the case of perfect complementarity of oligonucleotides to target rRNA. For both short and long oligonucleotide insecticides substantial decrease in rRNA concentration after rRNA hypercompensation in average by 3.75-4.25 fold, is explained by the work of DNA-guided rRNase, like RNase H1. We detected significant upregulation of RNase H1 after application of Coccus-11 in this study. On the contrary, for short and long random DNA oligos concentration of rRNA decreased in average by 2-3 fold after rRNA hypercompensation due to normal half-life of rRNAs in insect cells provided by ribonucleases. Fundamentally important, obtained results show completely new principle of regulation of rRNA expression in the cell via complementary interaction between rRNAs and unmodified antisense sequences of exogenous DNA. Practically important, this minimalist approach of using short antisense DNA dissolved in water is potent and eco-friendly innovation against sternorrhynchans and other pests, and reveals entirely new dimension to plant protection – DNA-programmable insect pest control.