Gene cloning, recombinant expression, and bioassay of an allatotropin in Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

Abstract

Background Allatotropin, a neuropeptide found in several invertebrates indirectly regulates vitellogenesis by stimulating juvenile hormone biosynthesis by the corpora allata. Here, we cloned and expressed the gene encoding allatotropin of Spodoptera litura (tobacco cutworm), a polyphagous pest in the Asian tropics. This study is aimed at studying the effect of recombinant protein on egg-laying in females of S. litura as it could be used as a method to control the pests from a reproductive perspective. Results The protein encodes a full-length open reading frame consisting of 173 amino acids and was rich in arginine (10%) and glutamic acid (9.3%). The theoretical pI of the protein was 5.47 and a hydrophobic signal peptide of 22 residues was predicted. The recombinant allatotropin was expressed in Escherichia coli BL21 (DE3) and purified by nickel exchange chromatography. The molecular weight of the recombinant protein was about 37 kDa and expression levels up to 5.3 mg/ml were achieved. Injection assay in vitro indicated that allatotropin induces egg-laying during the first scotophase after treatment in females of Spodoptera litura. Conclusion Allatotropin induces egg-laying in female moths and could be a potential molecule for the development of control strategies against Spodoptera litura. In this strategy, the protein if delivered to the females before mating may lead to accelerated egg deposition much before she encounters the male moths, thus the population being checked as the eggs deposited by the females are unfertilized. Thus, the present work could lead to the development of a protein based biopesticide resulting into a species-specific and an eco-friendly way of pest control.

Genome-wide identification and expression analysis of the mating-responsive genes in the male accessory glands of Spodoptera litura (Lepidoptera: Noctuidae)

“…Further on, using 2D gel electrophoresis and mass spectrometry, several potential molecules that modulate the female reproductive physiology and behaviour were characterized [ 33 ]. Subsequently, a recombinant allatotropin was revealed to induce egg-laying in virgin female moths of S. litura [ 34 ]. The genome of S. litura has also been sequenced and published by Cheng et al [ 14 ], thus providing resources for the identification of several mating-responsive genes.…”