Exogenous Hormones Affect Bt Protein Content of Two Bt Cotton Cultivars

Abstract

Bacillus thuringiensis (Bt) transgenic cotton (Gossypium hirsutum L.) has been widely planted in Asia. However, efficacy of the Bt protein to kill pests has been inconsistent. Effects of gibberellic acid (GA3) and dimethylpiperidinium chloride (DPC) on boll Bt protein content were investigated on ‘Sikang1’ and ‘Siza3.’ Treatment of DPC increased the Bt protein contents in carpel wall and cotton seed at 10 d after flowering (DAF) and 30 DAF in 2014 and 2015. However, Bt protein contents of the GA3 treatment only at 30 DAF were higher for both cultivars in comparison to the control. To further investigate the mechanism, we found the ability of protein synthesis (indicated by enzyme activities of nitrate reductase [NR], glutamic‐pyruvic transaminase [GPT], and glutamic oxaloacetate transaminase [GOT], as well as contents of total nitrogen, free amino acid, and soluble protein) in bolls increased markedly with the application of DPC for both cultivars. Further analysis showed that there were positive linear correlations between Bt protein content and NR, GPT, and GOT activities and total nitrogen and soluble protein contents (r = 0.925∗∗, r = 0.691∗∗, r = 0.703∗∗, r = 0.682∗, r = 0.693∗∗, respectively) in carpel wall of bolls. Thus, DPC is potentially an effective chemical application to increase boll Bt protein content.Core Ideas Dimethylpiperidinium chloride (DPC) application can bolster boll insect resistance. Significant linear positive correlation between Bt protein content and ability of synthesis the protein was found in boll shell. DPC increases Bt protein content through increasing ability of synthesis the protein.