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

摘要： 为了探讨种植密度对转基因抗虫棉纤维中杀虫(Bt)蛋白表达量的影响及其氮代谢机制，以Bt棉常规种泗抗1号和Bt棉杂交种泗抗3号为试验材料，比较1.5×10⁴、3.0×10⁴、4.5×10⁴、6.0×10⁴、7.5×10⁴ 株·hm^-2五个种植密度下转Bt棉杀虫蛋白表达量及其氮代谢的差异。结果表明，纤维中Bt蛋白表达量随种植密度增大呈上升趋势。相关分析表明，单株铃数、单铃体积、单铃干重与Bt蛋白表达量均呈显著负相关。纤维中氮代谢生理相关指标中，可溶性蛋白含量及谷氨酸丙酮酸转氨酶(GPT)和谷氨酸草酰乙酸转氨酶(GOT)活性随种植密度的增大而升高，但游离氨基酸含量、蛋白酶和肽酶活性随密度增大而下降。纤维中Bt蛋白表达量与可溶性蛋白含量、GPT和GOT活性呈显著正相关，而与游离氨基酸含量、蛋白酶和肽酶活性呈显著负相关。可见，提高种植密度降低了棉铃生长，但提高了纤维中Bt蛋白的表达量，且Bt蛋白表达量的提高与植株氮代谢生理密切相关。因此，在生产中通过协调种植密度既可以保持棉铃适度发育，又有利于提高棉纤维中Bt蛋白的表达量，为提高Bt棉产量器官抗虫性提供栽培基础。

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