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

Neda Arad; Jorge R Paredes-Montero; Mosharrof Hossain Mondal; Nathaniel Ponvert; Judith K Brown

doi:10.3389/finsc.2023.1283334

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

Front Insect Sci. 2023 Oct 18:3:1283334. doi: 10.3389/finsc.2023.1283334. eCollection 2023.

Authors

Neda Arad¹, Jorge R Paredes-Montero^{1

2}, Mosharrof Hossain Mondal¹, Nathaniel Ponvert¹, Judith K Brown¹

Affiliations

¹ School of Plant Sciences, The University of Arizona, Tucson, AZ, United States.
² Facultad de Ciencias de la Vida, Escuela Superior Politécnica del Litoral, ESPOL, Guayaquil, Guayas, Ecuador.

Abstract

Introduction: The 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.

Methods: Here, 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.

Results: The 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.

Discussion: Results 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.

Keywords: RNAi; biopesticide; citrus greening; potato psyllid; sugar metabolism; sugar transport.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Support for this research was provided by a grant from the USDA-NIFA CDRE grant 2018-70016-27411. A Teaching Assistantship was provided to NA by the School of Plant Sciences, UA College of Agriculture & Life Sciences.