Free amino acids composition and its changes at developmental stages of pink bollworm, Pectinophora gossypiella

Abstract

Free amino acid has an important role in physiological functions. Pink bollworm (PBW), Pectinophora gossypiella, was investigated for the free amino acid (FAAs) composition at immature stages (i.e., egg, larvae and pupae). Seventeen AAs were distinguished in the hole body of the different immature PBW stages. Essential AAs of tested stages of PBW consisted of threonine (THR), valine (VAL), methionine (MET), isoleucine (ILE), leucine (LEU), phenylalanine (PHE), lysine (LYS). Semi-essential AAs were histidine (HIS), arginine (ARG), cysteine (CYS), while non-essential AAs were aspartic acid (ASP), serine (SER), glutamic acid (GLU), glycine (GLY), alanine (ALA), tyrosine (TYR), and proline (PRO). The most prevailing FAAs, which exceeded 2 mg/100 mg, were LEU, LYS, ARG, ASP, GLU, ALA and TYR in all stages. Another AAs joined this group: VAL in larval stage, whereas its concentration was 2.28 mg/100 mg and exceeded that in egg by 16.92% and PHE & PRO in pupal stage, where it increased to 2.19 and 2.07 mg/100 mg, respectively. Also, in other words GLU was the most abundant FAAs in the egg stage (4.46%), while ASP and GLU were the most abundant FAAs in the larval and pupal stages 3.19 & 3.35% for ASP and 4.24 and 4.14% for GLU, respectively. On the other hand, CYS is the lowest abundant one recorded 0.68, 0.55 and 0.64% for egg, larvae and pupae, respectively). Furthermore, no qualitative changes in the FAAs composition of different immature stages of PBW, but there were quantitative changes. All FAAs increased from stage to other except for MET, CYS, SER, GLU and GLY, and the decreasing continued until pupal stage in the case of GLU, where it recorded 4.46, 4.24 and 4.14 mg/100mg in egg, larval and pupal stage, respectively. FAAs concentrations in egg were 1.21, 0.68, 1.78 and 1.82 mg/100mg for MET, CYS, SER, and GLY, respectively. These values decreased when PBW morphing from egg to larvae by 14.88, 19.12, 23.03 and 19.23%, respectively. After that, the change in FAAs concentration switch to increasing but still low from that recorded in egg in the case of CYS, SER & GLY represented 0.64, 1.52 & 1.50 mg/100mg, respectively. While, in MET the increasing in FAAs concentration when PBW morphing from egg to larvae continues until pupal stage and exceeded the value recorded in egg by 5.79% and 24.27% in larvae.