Biophysical and molecular evolutionary analysis reveals evidence of micro-evolution in the seminal fluid protein-Diazepam-binding inhibitor (DBI) of a Heliothine insect Helicoverpa armigera

Several seminal fluid peptides (SFP) are critical for gametogenesis and reproduction related physiological processes in insects. Male seminal fluid induced mating results in post mating physiological responses (PMR) in the female, further impacting the reproductive success of the mating pair. We have previously reported Diazepam-binding inhibitor (DBI) protein in the lepidopteran Helicoverpa armigera with species specific PMR response. In the present study, we study the biophysical properties of the DBI protein with bioinformatics methods, further; we map its origin and diversification in the Heliothine clade using molecular evolutionary methods. Our analysis suggests unique biophysical properties of the protein such as four α helices, high exposed and disordered regions. Further, the Proteins B-Value and ProNA values are indicative of its roles in lipid metabolism. High aliphatic amino-acid composition and conservation of protein domain at unique residues along with the hydrophobicity and transmembrane index are indicative of the relative solubility of amino acid residues conferring adaptability. Evolutionary analysis indicated the gene has undergone selection. Further, several unique evolutionary-constrained domain residues/regions (ECRs) in the protein are suggestive of their roles in reproduction related physiological mechanisms. Our data implicate that the protein DBI has undergone evolutionary variation through the micro-evolution process enabled through adaptive mutation in the proteins conferring flexibility and adaptability, thus ensuring genus and species specific specificity.