| The three varieties of the Bacillus thuringiensis (Bt) transgenic cotton that were popularizing in Jiangsu province even in China, were used as the experimental materials in this study, which were Kemian No. 1 that it was medium hybrid, Xinyang822 that it was conventional medium variety, and CCRI30 that it was pre-maturity variety. Because of unstable in the resistance to bollworm in the field, the study focused on the process of the nitrogen metabolism and the impacts of high temperature climate on the insecticidal protein expression of the Bt-transgenic cottons, which was closely linked with the insect-resistance of Bt-transgenic cotton. The research included two ways: One was to study the characteristic of Bt insecticidal protein expression and the nitrogen metabolism on the two medium-maturity varieties under the field condition with the parents as control. Another was to study the effects of high temperature(37℃) on the Bt insecticidal protein contents, the nitrogen metabolism and the endogenesis hormone at different development period. The aims were to seek the modulating measures for bolstering Bt insecticidal protein expressing in low insect-resistant period with regulating nitrogen metabolism effectively and gain high stable resistance to bollworm and yield together for the Bt -transgenic varieties in the field. The main results were as follows:1 The contents of Bt insecticidal protein in leaves were highest in full-squaring stage, and were lower in full-flowering and boll-open stages. The ten-day bolls had less Bt insecticidal protein between full-flower and boll-forming stage. Furthermore, the contents of Bt insecticidal protein in bolls were lower than in leaves at the same period. Further results showed that the contents of Bt insecticidal protein expressed in the hybrid Kemian No. 1 were more than in Xinyang822. For example, the Bt insecticidal protein content are 288.8ng/gfw in leaf of KemianNo 1 and only 159.2ng/gfw in Xinyang on August 8 .2 . Compared with the parents, the activities of nitrogen metabolism in Bt-transgenic cotton were enhanced and the abilities of protein synthesis were promoted. The activities of NR, which are more important in nitrogen metabolism in Bt- transgenic cottons, were higher than in their parents remarkably at all development stages.especially at full squaring and fully boll developing stages. The activity of NR increased 28.37% for Kemian No.l on June 25. The trends were same in the activities of GPT.. especially in boll-fonning forming period. The activities of GPT increased 39.04% for Kemian No. 1. As a whole, the activity of the proteinase reduced and the contents of soluble protein increased significantly for the Bt-transgenic cottons, (t-test values was 3.698 and 5.053 respectively). The above results indicated that the capacities of protein synthesis enhanced for Bt-transgenic cotton with the introduction of Bt gene. The intensity of nitrogen metabolism was higher for Kemian Nol than that for xingyang822 before full-blooming period, and the situation was on the contrary after the boll retention. .3, The expressing contents of Bt insecticidal protein were positive correlation significantly with the activities of the NR and GPT in the leaves, the coefficients were 0.8656 and 0 6434 respectively. Further studies showed that the dynamics of the endogenesis hormone GA3, in the development bolls were consistent with those of the Bt protein expressing and the relationship between of them was positive significantly(r= 0.8523). The result indicated that the GA3 may induced the synthesis of Bt protein in the bolls.4 The contents of Bt insecticidal protein reduced in all development stages by high-temperature stress for the three different types varieties. The Bt insecticidal protein contents decreased sharply in boll-forming period, reduced at some extent in full flowering stage, but not significant, and little reduction in the fully squaring stage. The results of the nitrogen metabolism assay showed further that the activities of NR and GPT... |
PDF Full Text Request