Transgenic plants expressing immunosuppressive dsRNA improve entomopathogen efficacy against Spodoptera littoralis larvae

Ilaria Di Lelio,Silvia Caccia,Giandomenico Corrado,Mariangela Coppola,Eleonora Barra,Rosa Rao

doi:10.1007/s10340-021-01467-z

Ilaria Di Lelio, Silvia Caccia + Show 4 more

Open Access

https://doi.org/10.1007/s10340-021-01467-z

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Abstract

Transgenic plants that express double-stranded RNA (dsRNA) targeting vital insect genes have recently emerged as a valuable new tool for pest control. In this study, tobacco plants were transformed to produce dsRNA targeting Sl 102 gene that is involved in the immune response of Spodoptera littoralis larvae, a serious lepidopteran pest of several crops. Experimental larvae reared on transgenic tobacco lines showed (1) a strongly reduced level of Sl 102 transcripts, which was positively associated with food consumption; (2) a substantial impairment of the encapsulation response mediated by hemocytes; and (3) a marked increase in the susceptibility to Xentari™, a Bacillus thuringiensis-based insecticide. Importantly, this approach may allow a reduction in the doses of B. thuringiensis used for field applications and enhance its killing activity on mature larvae. The results obtained thus support the use of immunosuppressive RNAi plants to enhance the performance of microbial insecticides on lepidopteran larvae.

Highlights

Tobacco plants expressing a double-stranded RNA (dsRNA) targeting Sl 102 immune gene induce its silencing upon ingestion in Spodoptera littoralis larvae, a serious crop pest
For the creation of an expression vector containing the construct to produce a dsRNA hairpin using the Gateway® Cloning System, a sequence of the Sl 102 gene was amplified with Sl102-attB1 Fw and Sl102-attB2 Rv primers using RNA extracted from S. littoralis hemocytes as the template
A number of potential traits have been tested for plant engineering against insect pests, the expression of Bt toxins remains the most widely used (Anderson et al 2019) and RNA interference (RNAi)-plants are the focus of most research efforts and market considerations (Zhang et al 2017; Anderson et al 2019; Fletcher et al 2020; Liu et al 2020)

Summary

Introduction

Tobacco plants expressing a dsRNA targeting Sl 102 immune gene induce its silencing upon ingestion in Spodoptera littoralis larvae, a serious crop pest. Interest in lectins was motivated by their ability to act as vectors for the delivery of insecticidal molecules with hemolymphatic targets, such as GNA-venom fusion proteins (Rao et al 1998; Foissac et al 2000; Sétamou et al 2002; Wang et al 2005; Nagadhara et al 2004; Trung et al 2006; Fitches et al 2012; Mi et al 2017), an approach that has been exploited in plants for the expression of chimeric proteins (Liu et al 2016; Nakasu et al 2014; Rauf et al 2019) It is worth mentioning the exploitation of the antinutritional properties of antivitamins (i.e., compounds that interfere with the biological function of vitamins) to develop insectresistant plants. By altering peritrophic matrix architecture, these enzymes affect the efficiency of macronutrient digestion in the insect midgut (Berini et al 2018)

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