Biology subjects

Escriche, B.

Publications and source records attributed to Escriche, B..

3 recordsLinked to original sources

bioRxiv2026

Synergism of Cry1Aa protein against Grapholita molesta (Busck) by a cadherin fragment from Spodoptera exigua (Hübner)

Bacillus thuringiensis (Bt) is currently the most commercialized biopesticide worldwide. Despite the success of Bt application in biological control programs, diverse strategies have been developed to enhance the toxicity of Bt toxins and delay the emergence of insect resistance, including the addition of cadherin fragments as a synergistic agent. In this study, the synergistic effect of two different cadherin fragments, one from a lepidopteran species, Spodoptera exigua (rSeCad1bp), and the other from a coleopteran species, Tenebrio molitor (rTmCad1p), was evaluated on the toxicity of Cry1Aa, Cry1Ab, and Cry1Ia against S. exigua and Grapholita molesta. Our results show that while the toxicity of Cry1 proteins to S. exigua was not affected by rSeCad1bp, the toxicity of Cry1Aa against G. molesta increased about 2.6-fold. No other synergistic or antagonist effects were observed. The potential mechanisms for the detected toxicity enhancement in G. molesta were studied, including protection against proteolysis, promotion of oligomerization, and increased binding to receptors on midgut brush border membrane vesicles (BBMV). Results revealed a slight increase in Cry1Aa binding to BBMV. These data highlight the great potential of using rSeCad1bp in combination with Cry1Aa for control of G. molesta. Key ContributionOur results show that the cadherin fragment from Spodoptera exigua synergized Cry1Aa toxicity against Grapholita molesta, but not to S. exigua. The synergistic effect observed might be partly associated with an increase in Cry1Aa binding to the target midgut membrane.

microbiology↗

bioRxiv2025

A Grapholita molesta (Lepidoptera: Tortricidae) cadherin in the 99C cadherin clade binds to Bacillus thuringiensis Cry1A proteins

Bt-cadherins, a particular type of midgut cadherins, act as receptors for Bacillus thuringiensis Cry1A pesticidal proteins. The aim of this work was to identify and validate the Cry1A cadherin receptor in Grapholita molesta (GmCad1). The GmCad1 gene was annotated by Blast genome mining using lepidopteran Bt-related cadherins. The phylogenetic analyses grouped GmCad1 with other Torticidae cadherins, in a different clade than the lepidopteran Bt-related cadherins. The in silico analysis of the GmCad1 showed a structure similar to that of the Bt-related cadherins, with 11 cadherin repeats (CRs), a transmembrane region, and an intracellular domain. The full-length mRNA sequencing confirmed GmCad1 expression in vivo in G. molesta guts. To validate the binding ability of Cry1A proteins to GmCad1, a cadherin fragment (CR7-CR11) was expressed and in vitro binding was studied demonstrating that Cry1Aa, Cry1Ab, and Cry1Ac bind to this region in a dose-dependent manner. In silico molecular docking analysis suggested that the interaction may involve mainly the Domains II of Cry1Ab and Cry1Ac, and the Domain III of Cry1Aa. This study provides the first evidence of a 99-C cadherin serving as a receptor for Cry1A in G. molesta.

molecular biology↗

bioRxiv2025

Lack of tolerance development following sublethal Cry1 proteins exposure in Spodoptera exigua

BACKGROUNDThe insecticidal proteins derived from Bacillus thuringiensis Berliner (Bt) have been effectively employed in controlling lepidopteran pests, notably in transgenic crops targeting Spodoptera species. However, concerns have arisen regarding the long-term efficacy due to the emergence of tolerant and resistant insect populations. Prior research suggested that repeated exposures to Bt may contribute tolerance, but the specific effects of sequential exposure to purified Cry1 proteins remain unclear. This study aimed to assess whether prior exposure of Spodoptera exigua (Huber, 1808) neonate larvae to sublethal concentrations of Cry1Ab and Cry1Ca proteins would heighten their tolerance upon subsequent exposure, and whether such effects would extend to their offspring. RESULTSPre-exposure to Cry1Ab did not affect larval responses to the toxin. For Cry1Ca, a slight increase was observed under one treatment condition, but the effect was not considered biologically relevant in practical terms. Similarly, transgenerational analysis revealed no enhancement of tolerance; rather, there was a negative impact on the offsprings response in some cases. CONCLUSIONThese findings indicate that although previous studies have documented that sublethal contact with bacterial preparations may significantly affect the insect tolerance, exposure to purified Cry proteins is unlikely to lead to the development of tolerance in S. exigua. Therefore, our findings suggest that sublethal exposure to these Cry1 proteins may not significantly affect the long-term efficacy of Bt-based pest management strategies relaying on them.

microbiology↗