Manipulate Cell Calmodulin Levels Of Tobacco Antioxidant Capacity And Its Physiological And Biochemical Mechanisms

Transgenic tobaccos expressing CaM/CaMBP genes have been developed by our lab to study the relationship among the CaM, oxidative stress resistance and antioxidant enzymes.This research includes three parts:For the first part, we measured the CaM activity of 22 transgenic tobacco lines expressing nuclear CaMBP by improved quantitative assay of plant calmodulin by phosphodiesterase, and selected three good transgenic tobacco lines(11, 18 and 25).For the second part, we used the T4-18 transgenic tobacco and T1.1 transgenic tobacco expressing cytosolic CaM as experimental material. During exposure to moderate oxidative stress caused by Paraquat and H2O2, Tc-inducible transgenic tobacco leaf disks expressing cytosolic CaM showed increased resistance to oxidative stress than those without Tc induction. Whereas transgenic tobacco leaf disks expressing nuclear CaMBP showed the reverse results, Tc-inducible transgenic tobacco leaf disks expressing nuclear CaMBP demonstrated reduced resistance to oxidative stress than tobacco leaf disks without Tc induction.At last, we measured the activity of superoxide dismutase (SOD), glutathione reductase (GR), guaiacol peroxidase (GPX), catalase (CAT)and ascorbate peroxidase (APX) treated by Tc, PQ and H2O2. The results demonstrated that the antioxidant enzyme activity of transgenic tobacco leaf disks expressing cytosolic CaM with Tc induction is higher than tobaccos without Tc induction. While the antioxidant enzyme activity of transgenic tobacco leaf disks expressing nuclear CaMBP with Tc induction is lower than tobaccos without Tc induction. This implied that CaM might play animportant role in resistance to oxidative stress of transgenic tobacco leaf disks through regulating antioxidant enzymes.