Induced Expression Of Cell Cambp Effect On The Regulation Of The Tobacco Heat Resistance And Its Physiological And Biochemical Mechanisms

Tc-inducible cytoplasmic CaMBP transgenic tobacco system was used as experimental material,which is firstly constructed by our laboratory ,to study the effects of lowering the the activity of cytoplasm CaM on the heat resistance,and their physiological and the biochemical mechanisms.The present research results included two parts:For the first part, we measured the CaM activity of 11 transgenic tobacco lines expressing cytosolic CaMBP by improved quantitative assay of plant calmodulin by phosphodiesterase. We selected 3 good transgenic tobacco lines(2.1, 4 and 19) whose CaM activity declined to 15-30% in seedlings or leaf disks after Tc-induced treatment .We found that 12 hours is the optimum Tc-inducible time from the curve of CaM activity during Tc-inducible 24 and 48 hours.For the second part, we used the three transgenic tobacco lines asexperimental material. Under 43# heat stress after 37# heat-shock treatment or non-heat-shock treatment, the heat resistance of Tc-inducible CaMBP transgenic tobacco leaf disks is weaker than without Tc-inducible leaf disks by electrolyte leakage and tissue vitality.The heat resistance of tobacco leaf disks without Tc-induced treatment was strengthened after heat-shock treatment,but the one with Tc-induced treatment has no significant change.These results confirmed that Ca-CaM messenger system is involved in the regulation of tobacco heat resistance.In addition, we used the leaf disks of line 2.1 as the experimental material to measure the activity of superoxide dismutase (SOD), glutathione reductase (GR), guaiacol peroxidase (GPX), catalase (CAT)and ascorbateperoxidase (APX). Whether under the heat-shock or non-heat-shock induction condition,the activity of the antioxidant enzyme with Tc-induction is higher than that without Tc-induction. At the same time ,the activity of the enzymes with Tc-inductin is more lower than that with Tc-induction after the heat stress with the heat-shock treatment.We also found that the activity of the antioxidant enzyme of tobacco expressing CaMBP has no significant change after heat stress,whether in heat-shock or non-haet- shock condition. So we might conclude that Tc-inducible CaMBP expression weakened the heat resistence and eliminated the heat-shock-induced heat risistance. And the decline of heat resistance is mediated by the regulation of CaM on the activity of antioxidant enzymes.