关键词: 转Bt基因抗虫棉, 棉铃, 杀虫（Bt）蛋白, 种植密度, 氮代谢

Abstract: In order to study the effect of planting density on the expression of insecticidal protein in the fiber of Bt transgenic cotton and corresponding nitrogen metabolism in this process, the Bt transgenic varieties including Sikang1 (conventional variety) and Sikang3 (hybrid) were used as experimental materials, five different of planting densities (1.5×10⁴, 3.0×10⁴, 4.5×10⁴, 6.0×10⁴, 7.5×10⁴ plants·hm^-2) were set  for studying the difference of Br protein expressions and nitrogen metabolism. The results showed that the expression levels of Bt protein in cotton fibers were enhanced as planting density increased. Correlation analysis showed that the boll number per plant, boll volume, and boll dry weight were all negatively correlated with the expression level of Bt protein. The related parameters in nitrogen metabolism were altered with planting density. The content of soluble protein, the activities of glutamic-pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) were increased under high planting density, but the content of free amino acid, the activities of protease and peptidase were all decreased under high planting density. The expression level of Bt protein was positively correlated with the content of  soluble protein and the activities of GPT and GOT, but negatively correlated with the content of free amino acid and the activities of protease and peptidase. In conclusion, with planting density increased, the boll growth was reduced and the expression level of Bt protein was elevated, while the expression level of Bt protein was closely related to nitrogen metabolism. Thus, in order to guarantee the insecticidal resistance, it was important to balance the boll development and the expression level of Bt protein, which should promote protein synthesis ability in cotton production.

Key words: Bt transgenic cotton, cotton boll, insecticidal (Bt) protein, planting density, nitrogen metabolism