关键词: 陆地棉, 红光, 蓝光, 愈伤组织增殖速度, 活性氧

Abstract:

【Objective】Upland cotton (Gossypium hirsutum) genetic transformation faces series of challenges such as a prolonged cycle and low efficiency, with the relatively slow proliferation rate of callus tissue being a critical factor contributing to the extended transformation period. This study aims to investigate the optimal light conditions for upland cotton callus growing. The establishment of this research endeavor is poised to accelerate callus proliferation and ultimately provide a technical foundation for shortening the period of cotton genetic transformation. 【Method】The hypocotyls of the upland cotton line WC were used as explants to induce callus tissues under four different lights: red, blue, red-blue (1:1), and white light (CK). The study aimed to investigate the varied effects of the different lights on callus induction and proliferation, determine the optimal light condition by comparing with the callus proliferation rate, morphological characteristics et al. under different light treatments. 【Result】Different light treatments had a significant impact on the callus induction and growth. The red-blue light treatment exhibited a most positive effect on both callus inducing and proliferation, which observed on the 7th and 15th day. The fresh weight of callus at 7 d under the red-blue light (0.39 g) was the heaviest, followed by the blue light (0.34 g), then the white light (0.24 g) and the red light (0.23 g). The same fresh weight order of the callus was observed at 15 d, with the treatment of the red-blue light (1.15 g) > blue light (0.98 g) > white light (0.69 g) > red light (0.51 g). The callus weight under red-blue light was 1.65 times heavier than the control, increased by 16.5% and 125.5% compared to the treatment of only blue or red light, respectively. In line with this, the callus proliferation rate in the second week under red-blue light was as high as 14.67%, which is twice to that of the red-light treatment (7.17%). The expression level of those genes promoted to cell proliferation and somatic embryo regeneration was consistent with the phenotype, the highest level was under the red-blue light treatment. Furthermore, the activity of the catalase (CAT) was significantly increased under the red-blue light treatment, while the content of reactive oxygen species (ROS) was lower than control. 【Conclusion】Employing different light conditions could result in the varied proliferation rate of cotton callus. The optimal light treatment is by red-blue light in a 1﹕1 ratio, followed by blue light and then white light. However, employing red light only does not favor the callus growth. The treatment of red-blue light (1﹕1) induces the expression of phytochromes and cryptochromes in the callus, increases the expression level of those genes promoted to callus growth. It also enhances the activity of catalase, reduces the content of ROS, and finally promotes the callus proliferation.

Key words: Upland cotton, red light, blue light, callus proliferation rate, active oxygen species