Role of Amino Acids in Protecting Pectinophora Gossypiella (Saund.) Against Strong Protein-Denaturing Activity of Phenolic Compounds in Cotton Plants

Abstract

o test if the generality of glycine secretion in the pink bollworm larvae related to the concentration of phenolic compounds (PCs), a feeding experiment with two concentrations of selected two PCs (pyrocatechol; Pyro & resorcinol; Res) was performed. Then, we determined and compared the lysine and glycine contents in the total body homogenate of treated and untreated 4 th instar larvae. Results showed that the lysine and glycine contents recorded were 2.29 & 1.47 mg/100mg of control larval body weight. Lysine content increased at low PCs concentration by 5.68 & 7.42% for Pyro and Res, respectively. On the other hand, its concentration decreased at high PCs concentration by 0.87 & 0.44%, respectively. On the other hand, glycine content generally decreased (except at low concentration of Pyro; 8.84%) by 4.76, 4.08 & 12.24%. Also, it could be noted that the generality of glycine secretion related to the concentration of PCs; whereas the less in glycine content was more notable in high concentration of PCs. And, the loss in glycine content was more than that for lysine. Also, studies extend to other amino acids (AA) and the results indicated that it could be grouped AA in 3 groups: 1. A high AA concentration (more than 3 mg/100mg): GLU and ASP acid. 2. A moderate AA concentration (more than 2 mg/100mg): VAL, LEU, LYS, ARG, ALA and TYR. 3. A low AA concentration (less than 2 mg/100mg): THR, ILE, PHE, HIS, CYS, SER, GLY and PRO. In the control PBW, glutamic acid and aspartic acid were present in high concentration (4.24 & 3.19 mg/100mg, respectively). As same manner with glycine; the losses in GLU and ASP contents were more than that for LYS. So, it could be used by PBW to overcome PCs toxicity. In addition, generally, at low PCs concentration, AA content increased except in the case of VAL and CYS. On contrast, at high PCs concentration, AA content decreased except in the case of MET, PHE, HIS and TYR. Commonly, it could be noted that Val, Cys, Gly and Ala had a higher percent of reduction. So, it means that other free amino acids may be used by some herbivores as counteractive agents against the denaturing activity of PCs.