High plant density increases seed Bt endotoxin content in Bt transgenic cotton

doi:10.1016/S2095-3119(20)63232-4

摘要/Abstract

摘要：

在棉花生产中，种植密度是用来控制棉铃分布、成铃情况和产量的常用栽培方法。2015年和2016年在大田条件下，研究了5种种植密度（PD1-PD5:15000；30000；45000；60000和75000株·ha^-1）对两个Bt棉品种泗抗1号（常规品种）和泗抗3号（杂交品种）Bt杀虫蛋白含量的影响。单株铃数、铃重、棉铃体积均随密度的增加而减少。当种植密度从15000株/hm2增加到75000株/hm2时，棉子中Bt杀虫蛋白含量增加，2015年花后40天SK-1和SK-3中Bt杀虫蛋白含量分别增加了66.5%和53.4%，2016年SK-1和SK-3分别提高了36.8%和38.6%。氮代谢结果分析表明，随着密度的增加，可溶性蛋白含量、谷氨酸丙酮酸转氨酶（GPT）和谷氨酸草酰乙酸转氨酶（GOT）活性增加，游离氨基酸含量、蛋白酶和肽酶活性降低。花后20天数据分析表明，棉子Bt杀虫蛋白含量与可溶性蛋白水平呈显著正相关，2015年在SK-1和SK-3中的相关系数分别为0.825**和0.926**，2016年在SK-1和SK-3中的相关系数分别为0.955**和0.965**。相比之下，棉子Bt杀虫蛋白水平与游离氨基酸含量呈显著负相关，2015年在SK-1和SK-3中的相关系数分别为-0.983**和-0.974**，2016年在SK-1和SK-3中的相关系数分别为-0.996**和-0.986**。为进一步证实Bt杀虫蛋白含量与氮代谢的关系，分析发现Bt杀虫蛋白含量与GPT和GOT活性呈正相关，与蛋白酶和肽酶活性呈负相关。综上所述，高种植密度增加了棉子Bt杀虫蛋白含量，该增加与单株铃数、铃重和铃体积的减少密切相关。此外，在高种植密度下，氮代谢的变化也有助于Bt杀虫蛋白含量的增加。

Abstract:

Plant density is the cultivation practice usually employed to manipulate boll distribution, boll setting and yield in cotton production. In order to determine the effect of plant density on the insecticidal protein content of Bacillus thuringiensis (Bt) cotton plants, a study was conducted in Yangzhou University of China in 2015 and 2016. Five plant densities (PD1–PD5, representing 15 000, 30 000, 45 000, 60 000, and 75 000 plants ha–1) were imposed on two Bt cotton cultivars, Sikang 1 (the conventional cultivar, SK-1) and Sikang 3 (the hybrid cultivar, SK-3). The boll number per plant, boll weight and boll volume all decreased as plant density increased. As plant density increased from 15 000 to 75 000 plants ha^–1, seed Bt protein content increased, with increases of 66.5% in SK-1 and 53.4% in SK-3 at 40 days after flowering (DAF) in 2015, and 36.8% in SK-1 and 38.6% in SK-3 in 2016. Nitrogen (N) metabolism was investigated to uncover the potential mechanism. The analysis of N metabolism showed enhanced soluble protein content, glutamic-pyruvic transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, but reduced free amino acid content, and protease and peptidase activities with increasing plant density. At 20 DAF, the seed Bt toxin amount was positively correlated with soluble protein level, with correlation coefficients of 0.825** in SK-1 and 0.926** in SK-3 in 2015, and 0.955** in SK-1 and 0.965** in SK-3 in 2016. In contrast, the seed Bt protein level was negatively correlated with free amino acid content, with correlation coefficients of –0.983** in SK-1 and –0.974** in SK-3 in 2015, and –0.996** in SK-1 and –0.986** in SK-3 in 2016. To further confirm the relationship of Bt protein content and N metabolism, the Bt protein content was found to be positively correlated with the activities of GPT and GOT, but negatively correlated with the activities of protease and peptidase. In conclusion, our present study indicated that high plant density elevated the amount of seed Bt protein, and this increase was associated with decreased boll number per plant, boll weight and boll volume. In addition, altered N metabolism also contributed to the increased Bt protein content under high plant density.

Key words: Bt cotton , plant density , Bt insecticidal protein , nitrogen metabolism

. [J]. Journal of Integrative Agriculture, 2021, 20(7): 1796-1806.

CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, CHEN De-hua. High plant density increases seed Bt endotoxin content in Bt transgenic cotton[J]. Journal of Integrative Agriculture, 2021, 20(7): 1796-1806.

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