Insecticidal Activity of a Vip3Ab1 Chimera Is Conferred by Improved Protein Stability in the Midgut of Spodoptera eridania

Abstract

Vip3A proteins are important for the control of spodopteran pests in crops, including Spodoptera frugiperda (fall armyworm). Native Vip3Ab1 controls S. frugiperda, but it is ineffective against S. eridania (southern armyworm), a major pest of soybean in South America. Recently, a Vip3Ab1 chimera with a modified C-terminus was described, Vip3Ab1-740, which has increased potency against S. eridania while maintaining activity against S. frugiperda. As S. frugiperda and S. eridania are differentially susceptible to Vip3Ab1, experiments were conducted to identify and understand the mechanism by which this expanded potency is conferred. The role of protein stability, processing, and in vivo effects of Vip3Ab1 and Vip3Ab1-740 in both of these species was investigated. Biochemical characterization of the midgut fluids of these two species indicated no obvious differences in the composition and activity of digestive enzymes, which protease inhibitor studies indicated were likely serine proteases. Histological examination demonstrated that both proteins cause midgut disruption in S. frugiperda, while only Vip3Ab1-740 affects S. eridania. Immunolocalization indicated that both proteins were present in the midgut of S. frugiperda, but only Vip3Ab1-740 was detected in the midgut of S. eridania. We conclude that the gain of toxicity of Vip3Ab1-740 to S. eridania is due to an increase in protein stability in the midgut, which was conferred by C-terminal modification.

Biología de Spodoptera eridania (Stoll) en el cultivo de uva (Vitis vinifera L.) en condiciones de laboratorio

“…Sin embargo, dichas condiciones también favorecen la presencia de insectos plagas y enfermedades que amenazan a este cultivo adquiriendo mayor importancia como factores adversos. Entre los insectos plagas tenemos a los lepidópteros y entre ellos a Spodoptera eridania (Stoll, 1782), especie polífaga originaria de los trópicos americanos (Capinera, 2018), que recientemente invadió África (Weinberg et al, 2022;Sampaio et al, 2020), plaga importante de muchos cultivos (Pogue, 2022), en particular de maíz, soja, algodón, camote y tomate y en los últimos años en el cultivo de uva (Bortoli et al, 2012;Bowling et al, 2019, de Sousa et al, 2019Luz et al, 2019;Machado et al, 2020;CABI, 2021;Parra et al, 2022;Scudeler et al, 2023) debido tanto a la tolerancia a la alta densidad de la población así como, por el alto grado de defoliación causada por la alimentación de las larvas (Bortoli et al, 2012;Sardina de Souza et al, 2012). Cuando esta especie se propagó a África occidental fue registrado como invasiva (Goergen, 2018), y ha sido catalogada como plaga cuarentenaria A1 para Europa (Bragard et al 2020).…”