The Effect Of High Temperature On The Insecticidal Properties And Nitrogen Metabolism Of Bt Cotton Reproductive Organ

With the different type of Bt cotton varieties that the Bt genes were from China and America respectively as the tested materials, they were the domestic cultivars:sikang1(conventional varieties), sikang3(Hybrid),.America cultivars:99B (conventional varieties), Daiza1(hybrid),.The potted experiment was conducted at agriculture college,yangzhou univericity,4high temperature regiments (34℃,36℃,38℃,40℃) in2011,6high temperature regiments (34℃,36℃,38℃,40℃,42℃,44℃)in2012were applied during the squaring stage and the boll stage at the artificial climate chambers for24hours.,Based on the experimental results of2011. the cotton plants were stressed further under the threshold of the high temperature for3,5and7days during the squaring stage and the boll stage in2012. The content of insecticidal protein at the reproductive organs, the compounds and key enzymes of nitrogen metabolism under above high temperature stresses were measured. The main results were as follows:1. In comparison to the control(32℃),the insecticidal protein concentration of the reproductive organs decreased under34℃,36℃,38℃and40℃for24hours during the squaring stage and the boll stage. For cultivar Sikangl,the insecticidal protein content of the square decreased by3.84%,8.20%,35.36%and47.18%respectively at the squaring stage,, the insecticidal protein content of the boll wall decreased by6.53%,12.71%,53.02%and69.45%, the insecticidal protein content of the fiber decreased by9.12%,18.99%,49.44%and70.03%during boll period. For cultivar Sikang3, the insecticidal protein content in the square decreased by1.71%,4.51%,34.21%and42.74%, in the boll wall, decreased by4.00%,8.14%,14.27%and64.76%respectively. in the fiber decreased by6.81%,12.99%,20.56%and67.18%respectively. Similar rsults were detected for the cultivars from America. The experiment in2012also showed same effects for reduction of insecticidal contents in square and boll under stress of6high temperature levels. From above results, significant reductions of the insecticidal concentration in square were all found above38℃, in boll were detected above38℃for conventional cultivars, above40℃for hybrid cultivars. Therefore, we thought that38℃may be threshold that high temperature resulted in the decrease of Bt insecticidal protein in the square,38-40℃may be the threshold that high temperature resulted in the decrease of Bt insecticidal protein in the boll. The related compounds content and the key enzyme activities of the nitrogen metabolism at the reproductive organs under the high temperature stress showed significant decrease of the soluble protein content, glutamate pyruvate transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, increase sharply of the free amino acid content, the activities of the protease and peptidase.The conventional cultivars had greater change than the hybrid cultivars in nitrogen metabolism. The correlation analysis showed that significant positive correlations were detected between the insecticidal protein content and the content of the soluble protein content, GPT and GOT activity, the correlation coefficients were0.946**,0.940**,0.929**respectively, and significant negative correlations were found between the insecticidal protein content and the content of the drift amino acids and the activity of the protease and peptidase showed (the correlation coefficients were-0.883**,-0.883**,-0.884**respectively). Therefore, high temperature result in the degradation of the insecticidal protein concentration of the reproductive organs significantly,This may be the decrease of protein contont results from reducing protein synthesis under the high temperature.Among the the varieties of Bt cotton in different genes and different types showed that, affected by high temperature, With the different type of Bt cotton varieties that the Bt genes were from China were higher than the America cultivars,the conventional cultivars were higher than the hybrid cultivars.2.Two different types were stressed further under the threshold of the high temperature for3,5and7days at38℃in squaring stage and at40℃in boll stage showed that, the expression of the insecticidal protein in the reproductive organs have been significantly decreased within3days, and then the contents reduced slightly. At the squaring stage,for the domestic hybrid varieties Sikang3, the insecticidal protein content of the square at3,5and7days, In comparison to the control were decreased by18.71%,25.36%and32.67%.For the domestic conventional varieties Sikangl, the insecticidal protein content of the square were decreased by26.54%,33.20%and42.15%.The downward trends of boll wall and fibre was the same with square.The related compounds content and the key enzyme activities of the nitrogen metabolism at the reproductive organs under the sustained temperature stress showed as well that the soluble protein content, GPT and GOT activities decreased significantly, the free amino acid content, the activities of the protease and peptidase increased sharply.such as Sikang3, In comparison to the control,the expression of soluble protein of square decreased by21.00%,28.43%and42.41%, the free amino acid content of square increased by73.50%,96.39%and111.47%. The correlation analysis also showed that significant positive correlations were detected between the insecticidal protein content and the content of the soluble protein content, GPT and GOT activity, the correlation coefficients were0.947**,0.913**,0.950**respectively, and significant negative correlations were found between the insecticidal protein content and the content of the drift amino acids and the activity of the protease and peptidase showed (the correlation coefficients were-0.610**,-0.947**,-0.966**respectively).