Abstract
BackgroundAllatotropin, 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.ResultsThe 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.ConclusionAllatotropin 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.
Highlights
Allatotropin, a neuropeptide found in several invertebrates indirectly regulates vitellogenesis by stimulating juvenile hormone biosynthesis by the corpora allata
A strategy well established in this study is that allatotropin if delivered to the females before mating may lead to accelerated egg deposition much before she encounters the male moths, the population being checked as the eggs deposited by the females are unfertilized
The nucleotide sequence of allatotropin isoform X2 (NCBI Reference Sequence: XM_022974503.1) identified from Spodoptera litura genome was artificially synthesized and ligated into pET32a + vector series fused with the 109 aa Thioredoxin tag
Summary
Allatotropin, a neuropeptide found in several invertebrates indirectly regulates vitellogenesis by stimulating juvenile hormone biosynthesis by the corpora allata. Allatotropin, a member of the family of myoactive neuropeptides found in several invertebrate phyla stimulates juvenile hormone (JH) biosynthesis in corpora allata (CA) (Elekonich & Horodyski, 2003). Lacanobia oleracea, injection of AT 1 peptide into the sixth instar larvae led to increase in mortality rate, reduction in body weight and delay in pre-pupal development as a consequence of JH synthesis (Audsley et al, 2001). Another allatotropin reported as Spofr-AT 2 was identified and characterized by cloning the cDNA encoding Manse-AT in Spodoptera frugiperda (Abdellatief et al, 2004). There are no reports on allatoregulating neuropeptides or their functions associated with egg production in Spodoptera litura
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