Effect Of Both High Temperature And After The Stress Termination On The Bt Insecticidal Protein Of The Reproductive Organ And Correlative Physiological Mechanisms In Bt Cotton

The experiments were conducted at Key Laboratory of Genetics and Physiology, Yangzhou University.Bt cotton conventional cultivar Sikang-1and hybrid cultivar Sikang-3which have the same genetic background were used as the tested materials. During2012cotton growth season, the potted cotton samples at squaring stage and bolling stage resepectively were moved to climax box where the temperatures were38/25℃and39/27℃at day/night for4d,7d and10d resepectively, the squares and bolls were collected to measure the Bt protein concentration and nitrogen metabolic physiology; During2013cotton growth season, the potted cotton samples at squaring stage and bolling stage resepectively were moved to climax box where the temperatures were38℃and39℃respectively for72h,96h repectively, the samples were moved to natural condition after the stresses termination and the squares and bolls were collected to measure the Bt protein concentration and nitrogen metabolic physiology at0,12,24,48,72,96hours after the high temperature termination. The results were as follows:1、In comparison to the corresponding control, the square Bt toxin content for Sikang-1decreased by0.72%,14.18%and31.50%at bud stage under temperature treatment38/25℃for4,7and10days respectively, the bollwall Bt toxin content for Sikang-1decreased by2.82%,19.07%and44.48%, the fiber Bt toxin content decreased by3.18%,20.24%and42.64%at boll stage under temperature treatment39/27℃for4,7and10days respectively. For the cultivar Sikang-3, the square Bt toxin content decreased by0.61%,11.32%and25.21%at bud stage under temperature treatment38/25℃for4,7and10days respectively, the bollwall Bt toxin content decreased by2.26%,15.26%and33.23%respectively, the fiber Bt toxin content decreased by2.67%,16.96%and33.68%at boll stage under temperature treatment39/27℃for4,7and10days respectively. These results showed that the Bt toxin content at squares and bolls decreased slightly within4days of the temperature treatments, however, the contents reduced significantly after7days temperature stress, and the reduced extents of the Bt protein content at the boll were heavier than that at the squares. It came to the conclusion that the Bt protein concentration reduced markedly under high temperature with alternating temperature at day/night for more than7day.The related compounds content and the key enzyme activities of the nitrogen metabolism at the reproductive organs under temperature treatment showed that the free amino acid content increased in bud and boll significantly, the soluble protein content and GPT activities decreased sharply, the activities of the protease increased sharply after the temperature treatments duration for more than4days. The changing range of the related compounds content and the key enzyme activities of the nitrogen metabolism for Sikang-1are larger than that for hybrid Sikang-3. Correlation analysis showed that there were significant positive correlation between Bt toxin content and the content of the soluble protein content, the activity of the glutamate pyruvate transaminase (GPT) respectively (the correlation coefficients were0.895**and0.889**in bud;0.954**and0.988**in bollwall;0.984**and0.979**in fiber); there were significant negative correlation between Bt toxin content and the free amino acids content, the activity of the protease respectively(the correlation coefficients were-0.929**and-0.946**in bud;-0.924**and-0.775**in bollwall;-0.758**and-0.797**in fiber).2. The Bt insecticidal protein contents in reproductive organs were able to recover to the corresponding control level, however, the recovery time of Bt protein content was longer with the longer high temperature temperature period after termination of high temperature treatment38℃at squaring stage,39℃at boll stage for72hours and96hours respectively. Compared to the corresponding control, the square Bt insecticidal protein contents of cultivar Sikang-1were being35.14%.41.11%.51.91%.74.77%.100.42%.100.75%of the corresponding control at Oh,12h,24h,48h,72h,96h respectively after the ending of the high temperature treatment for72h, the result showed that the square Bt insecticidal protein content could recover to the corresponding control level at72h after72h high temperature stress termination. For cultivar Sikang-3, the square Bt insecticidal protein contents of cultivar Sikang-3were being41.90%.59.16%.78.44%,99.50%.100.13%.98.43%of the corresponding control at Oh,12h,24h,48h,72h,96h respectively after the ending of the high temperature treatment for72h, the result showed that the square Bt insecticidal protein content could recover to the corresponding control level at48h after72h high temperature stress termination. There were similar recovery trend for Bt toxin content in boll wall and fiber. However, the Bt toxin content in both boll wall and fiber in cultivar Sikang-1recovered to the corresponding control level at72h after termination of the high temperature stress, and at48h after termination of the high temperature stress for cultivar Sikang-3.Compared to the corresponding control, the square Bt insecticidal protein contents of cultivar Sikang-1were being28.46%,33.15%,41.67%,60.75%.84.80%,101.90%of the corresponding control at Oh,12h,24h,48h,72h,96h respectively after the ending of the high temperature treatment for96h, the result showed that the square Bt insecticidal protein content could recover to the corresponding control level at96h after96h high temperature stress termination. For cultivar Sikang-3, the square Bt insecticidal protein contents of cultivar Sikang-3were being30.18%,39.64%,58.84%,85.93%,100.78%,100.61%of the corresponding control at Oh,12h,24h,48h,72h,96h respectively after the ending of the high temperature treatment for96h, the result showed that the square Bt insecticidal protein content could recover to the corresponding control level at72h after96h high temperature stress termination. There were similar recovery trend for Bt toxin content in boll wall and fiber. However, the Bt toxin content in both boll wall and fiber in cultivar Sikang-1recovered to the corresponding control level at96h after termination of the high temperature stress, and at72h after termination of the high temperature stress for cultivar Sikang-3.Correlation analysis showed that there were significant positive correlation between Bt toxin content and the content of the soluble protein content, the GPT activity, glutamate oxaloacetate transaminase (GOT) activity respectively(the correlation coefficients were were0.964**,0.981**and0.971**respectively in bud;0.965**,0.952**and0.957**respectively in bollwall;0.962**,0.975**and0.956**respectively in fiber); there were significant negative correlation between Bt toxin content and the free amino acids content, the activity of the protease, peptide enzyme respectively(the correlation coefficients were-0.894**,-0.912**and-0.834**respectively in bud;-0.938**,-0.885**and-0.877**respectively in bollwall;-0.906**,-0.902**and-0.841**respectively in fiber).