Recovery Characteristics of Cry1Ac Endotoxin Expression and Related Physiological Mechanisms in Bt Transgenic Cotton Squares after High-Temperature Stress Termination

Zhenyu Liu,Tianfan Wu,Xiang Zhang,Guixia Wang,Zhongning Zhang,Hanjia Li,Chenxia Zhang,Dehua Chen

doi:10.3390/agronomy12030668

Abstract

High-temperature stress reduces the endotoxin expression of the insecticidal gene (Cry1Ac) in transgenic Bacillus thuringiensis (Bt) cotton and affects nitrogen metabolism. However, its effects on Cry1Ac endotoxin expression after high-temperature stress termination remain unclear. In order to investigate the effect of high-temperature stress on the expression of insecticidal proteins in Bt cotton squares, the conventional Sikang-1 cultivar and hybrid Sikang-3 cultivar were used as the experimental materials. The potted cotton plants in the squaring stage were moved to an artificial climatic chamber at 38 °C for 72 h and 96 h in 2017 and 2018, respectively, and plants were moved to the climate chamber where the control cotton plants were located (at 27 °C). Then, cotton squares were collected to measure the Bt protein concentration and nitrogen metabolism physiology at 0, 12, 24, 48, 72 and 96 h after high-temperature stress termination, respectively. The Cry1Ac endotoxin expression of the squares could be recovered to the corresponding control level and a longer recovery time was required as the high-temperature stress period increased. Therefore, the recovery degree of Cry1Ac endotoxin expression of cotton squares can be predicted according to the duration of high-temperature stress, which may provide a reference for the rational control of Helicoverpa armigera and related pests in cotton production.

Highlights

Since its initial commercialization in the 1990s, Bacillus thuringiensis (Bt) transgenic cotton has been widely grown worldwide [1–4], increasing the economic prosperity of cotton growers, reducing the need for chemical insecticides and, allowing for improved worker safety and environmental pollution [5,6]
Wang et al found that the physiological activity of nitrogen metabolism in the boll shell of transgenic Bt cotton was changed after high-temperature stress at the peak of the boll stage [20]
This further revealed that the time required for Bt protein expression in cotton squares to recover to the control level at the peak of the squaring stage was different after 72 h and 96 h of high-temperature stress at 38 ◦C

Summary

Introduction

Since its initial commercialization in the 1990s, Bacillus thuringiensis (Bt) transgenic cotton has been widely grown worldwide [1–4], increasing the economic prosperity of cotton growers, reducing the need for chemical insecticides and, allowing for improved worker safety and environmental pollution [5,6]. Benedict and Sachs et al studied the insect resistance, Bt protein expression and soluble protein changes of the Bt cotton plants in different regions of the United States They reported that temperature, soil moisture and fertilizer affected the expression of insect resistance genes of the Bt cotton plants [13]. Chen et al studied the recovery characteristics of Bt protein expression in leaves after high- and low-temperature stress termination. They did not consider the recovery of insect resistance of the reproductive organ that cotton bollworm preferred under temperature stress [24]. Further studies on the changes of insecticidal protein expression in Bt cotton squares after high-temperature stress termination are of great theoretical and practical significance in order to characterize the recovery of insect resistance as well as its safe application

Methods

Results

Discussion

Conclusion