Expression of Syntaxin 18 in Peregrinus maidis and Design of Its dsRNA Fragments towards a Targeted RNAi Biopesticide for Insect Vector Control

Maize mosaic virus (MMV) is a plant virus that is transmitted by the corn planthopper, Peregrinus maidis Ashmead (Hemiptera: Delphacidae) in a persistent and propagative manner. MMV is the causal agent for mosaic disease that can cause significant loss in corn yield. Management is focused on controlling insect vector population. The molecular mechanisms of virus transmission by the insect vector are not fully understood. Previously, we identified a receptor for MMV, the P. maidis syntaxin 18 (PmStx18). PmStx18 interacts with the viral glycoprotein and potentially facilitates MMV recognition and entry into the vector, enabling virus proliferation. Stx18 is a key component of the vesicular trafficking machinery and also plays a critical role in neurotransmitter release in insects. In this work, we investigated the expression of PmStx18 in different developmental stages and major parts of the insect vector. Primers were designed to generate templates for synthesis of double-stranded RNA fragments. A 374-bp amplicon was selected and gene-specific sequences were flanked by T7 promoter sequences for in vitro transcription. Results showed a significant difference in the expression of Stx18 in the different developmental stages of P. maidis but not between male and female adults and major body parts. In vitro transcription products indicated optimal reaction conditions and protocol suitability. The findings establish the initial steps for developing RNAi-based approach in controlling MMV transmission by targeting Syntaxin-18 in P. maidis. Further investigations are needed to evaluate the efficacy of this approach.