RNAi Targets in Agricultural Pest Insects: Advancements, Knowledge Gaps, and IPM

Abstract

The unprecedented target-specificity of double-stranded RNA (dsRNA), due to its sequence-specific mode of action, puts dsRNA at the forefront of biosafe insecticide technology. Since 2007, sensitive target genes have been identified in numerous crop pest insects, with an end goal of applying RNA interference (RNAi) in pest management. Key RNAi targets identified include genes involved in (1) feeding and digestion, (2) production of dsRNases, (3) resistance to insecticides and plant allelochemicals, (4) reproductive fitness, and (5) transmission of plant viruses. Despite the advances, there remain critical knowledge gaps in each of these areas. Particular emphasis must be placed on ensuring RNAi's compatibility with integrated pest management (IPM), via further identification of molecular targets that reduce crop damage while sustaining pest (host) populations for highly specialized biocontrol agents, the latter representing a core pillar of IPM.

Current Scenario of Exogenously Induced RNAi for Lepidopteran Agricultural Pest Control: From dsRNA Design to Topical Application

“…The precaution of excluding cross-kingdom sRNAs (ck-sRNAs) helps avoid undesirable effects on non-target species. For this purpose, when preparing samples for the sequencing step, it is necessary to treat samples in order to avoid contamination with other organisms (plant cells, endogenous microbiota, parasites) [50], determine the number of biological replicates and calculate the correct amount of reads to achieve sufficient genome coverage (typically three biological replicates with 5-10 million reads each). Sequencing of sRNAs is carried out using a wide variety of high-throughput technologies [51,52], including MiSeq and HiSeq (Illumina Inc., San Diego, California, EUA), SMRT PacBio (Pacific BioSciences, Menlo Park, California, EUA), and Roche 454 technologies (Branford, Connecticut), depending on the output range and total reads per run required [53].…”

Uniting RNAi Technology and Conservation Biocontrol to Promote Global Food Security and Agrobiodiversity

“…As with any pesticide, the development of resistance must be considered; indeed, the potential for dsRNA resistance has recently been demonstrated in two herbivorous beetles, through selective breeding for this trait ( Khajuria et al, 2018 ; Mishra et al, 2021 ). This represents a major hurdle for RNAi technology in crop protection ( Khajuria et al, 2018 ; Yoon et al, 2018 ; Romeis and Widmer, 2020 ; Willow et al, 2021b ; Mishra et al, 2021 ; Willow and Veromann, 2021 ; Christiaens et al, 2022 ; Darlington et al, 2022 ). Pesticide resistance management strategies that are already in use could potentially be adapted for RNAi.…”

“…The elimination of applied dsRNA in the agroecosystem after the relevant period of pest management not only reduces non-target organisms’ exposure to dsRNA, but also limits the target’s duration of exposure (especially in the case of dsRNA spray), thereby reducing the chance of resistance development. Furthermore, limiting the period of exposure can encourage the persistence of specialized biocontrol agents that rely on host pest availability ( Willow et al, 2021b ).…”

Towards dsRNA‐integrated protection of medical Cannabis crops: considering human safety, recent‐ and developing RNAi methods, and research inroads

“…51,52 This sequence-specificity permits the capacity for identifying a wide array of precise molecular targets in a given pest species, allowing triggering of respective phenotypes, including, but not limited to, those potentially most compatible for simultaneously benefiting from biological control services. 53 Although such precise molecular targeting is the cornerstone supporting development of RNA-based pest management practices, the concurrent shaping of a meaningful risk assessment standard for unintended environmental effects of these applications is still in its infancy. The main plausible unintended effects of applied dsRNA include knockdown of important mRNA transcripts in nontarget organisms via direct exposure or other food web associations, and the activation of immunomodulatory responses in nontarget organisms, both of which could result in sublethal or lethal effects in the nontargets.…”