Functional expression of a peritrophin A-like SfPER protein is required for larval development in Spodoptera frugiperda (Lepidoptera: Noctuidae)

Claudia Rodríguez-De La Noval,Siliang Huang,Denis J Wright,Lianet Rodríguez-Cabrera,Daily Hernandez,Luis A Espinosa,Camilo Ayra-Pardo,Yunchao Kan,Orlando Borras-Hidalgo,Laurent Izquierdo,Pilar Tellez-Rodríguez,Milagro Ponce,Ivis Moran-Bertot

doi:10.1038/s41598-019-38734-0

Abstract

Peritrophins are associated with structural and functional integrity of peritrophic membranes (PM), structures composed of chitin and proteins. PM lines the insect midgut and has roles in digestion and protection from toxins. We report the full-length cDNA cloning, molecular characterization and functional analysis of SfPER, a novel PM peritrophin A protein, in Spodoptera frugiperda. The predicted amino acid sequence indicated SfPER’s domain structure as a CMCMC-type, consisting of a signal peptide and three chitin-binding (C) domains with two intervening mucin-like (M) domains. Phylogenetic analysis determined a close relationship between SfPER and another S. frugiperda PM peritrophin partial sequence. SfPER transcripts were found in larvae and adults but were absent from eggs and pupae. Chitin affinity studies with a recombinant SfPER-C1 peritrophin A-type domain fused to SUMO/His-tag confirmed that SfPER binds to chitin. Western blots of S. frugiperda larval proteins detected different sized variants of SfPER along the PM, with larger variants found towards the posterior PM. In vivo suppression of SfPER expression did not affect susceptibility of larvae to Bacillus thuringiensis toxin, but significantly decreased pupal weight and adult emergence, possibly due to PM structural alterations impairing digestion. Our results suggest SfPER could be a novel target for insect control.

Highlights

Peritrophins are associated with structural and functional integrity of peritrophic membranes (PM), structures composed of chitin and proteins
PMs can be classified into two types depending on whether they are secreted by the whole midgut epithelium (Type I) or by the cardia (Type II), an organ near the foregut-midgut junction[2,9,10]
Phylogenetic analysis found SfPER to be related to the 38 S. frugiperda PM polypeptides (SfPMP) previously identified in S. frugiperda, of which only 15 have a complete sequence verified with domains structure elucidated[41]

Summary

Introduction

Peritrophins are associated with structural and functional integrity of peritrophic membranes (PM), structures composed of chitin and proteins. PM lines the insect midgut and has roles in digestion and protection from toxins. We report the full-length cDNA cloning, molecular characterization and functional analysis of SfPER, a novel PM peritrophin A protein, in Spodoptera frugiperda. In vivo suppression of SfPER expression did not affect susceptibility of larvae to Bacillus thuringiensis toxin, but significantly decreased pupal weight and adult emergence, possibly due to PM structural alterations impairing digestion. Peritrophins are integral, strongly-bound PM proteins that directly interact with the chitin fibrils scaffold through chitin-bnding domains (CBDs) and can only be released from the PM by strong denaturants[13,14]. CBDs carry multiple cysteine residues that form intra-domain and inter-molecular disulfide bridges[13,14]. PM peritrophins may possess one or more highly glycosylated mucin-like (MD) domains[15,16,17]

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Conclusion