RNA interference-mediated knockdown of genes involved in sugar transport and metabolism disrupts psyllid Bactericera cockerelli (Order: Hemiptera) gut physiology and results in high mortality

Abstract

IntroductionThe causal agent of zebra chip of potato and vein-greening diseases of tomato is "Candidatus Liberibacter solanacearum" (CLso), a fastidious bacterium transmitted by the potato psyllid. In the absence of disease-resistant cultivars, disease management has relied on minimizing vector population size to reduce CLso transmission, which requires frequent insecticide applications. There is growing interest in the use of RNA interference (RNAi) technology to supplant traditional insecticides with biopesticides. This requires knowledge of genes essential for insect livelihood whose knockdown leads to significant mortality or other phenotypes. Such candidate genes can be evaluated by reverse genetics approaches to further corroborate predicted gene function.MethodsHere, five potato psyllid genes involved in sugar homeostasis in the potato psyllid gut, α-glucosidase1 (AGLU1), aquaporin2 (AQP2), facilitated trehalose transporter1 (TRET1), Trehalase1 (TRE1), and Trehalase2 (TRE2), were investigated as candidates for effective gene silencing. Potato psyllid dsRNAs were designed to optimize knockdown of gene targets. Third instar PoP nymphs were given a 48-hr ingestion-access period (IAP) on individual or groups of dsRNA in 20% sucrose. Mortality was recorded 0, 3, 5, 7, and 9 days post-IAP. Gene knockdown was analyzed 9 days post-IAP by quantitative real-time reverse-transcriptase polymerase chain reaction amplification. ResultsThe individual or stacked dsRNA combinations resulted in 20-60% and 20-40% knockdown, respectively, while subsequent psyllid mortality ranged from 20-40% to >60% for single and stacked dsRNA combinations, respectively. Reverse genetics analysis showed that simultaneous knockdown of the five selected candidate genes with predicted functions in pathways involved in sugar-homeostasis, metabolism, and -transport yielded the highest mortality, when compared with single or combinations of targets. DiscussionResults confirmed the functions afforded by psyllid gut genes responsible for osmotic homeostasis and sugar metabolism/transport are essential for livelihood, identifying them as potentially lucrative RNAi biopesticide targets and highlighted the translational relevance of targeting multiple nodes in a physiological pathway simultaneously.

Unveiling the frontiers of potato disease research through bibliometric analysis

“…Insects were not only mechanically damaging potato plants but also transmitting pathogens such as bacteria and viruses to plant wounds. For example, in the United States, research was mainly focused on potato psyllid, which was the vector of CLso, and ultimately triggered the ZC affecting the commercialization of potatoes (Arad et al, 2023a ), whereas research on pests in India was focused on whiteflies and the spread of viruses such as tolcndv. In other words, national research on pest suppression was also based, in part, on the reduction of alternative hosts for pathogens and thus the incidence of other diseases (Kumar et al, 2021 ).…”

“…For instance, a spray-based delivery method for double-stranded RNA-induced gene silencing (SIGS) to combat potato Y virus infections was developed by Samarskaya et al ( 2023 ). Additionally, Arad et al ( 2023a ) successfully silenced five genes related to sugar homeostasis in the gut of the potato woodlouse using RNAi technology, resulting in over 60% mortality of the potato psyllid, suggesting a potential application of RNAi as a biopesticide target. Although biocontrol was employed in various forms, its essence was still the pursuit of friendly biological products with high control efficiency and long-lasting effects, making it one of the main control strategies for the future.…”