ABA promotes assimilate transport to cotton bolls by inducing the gene expression of acid invertase and sucrose synthase after mepiquat chloride treatment

Mepiquat chloride (MC) is an indispensable plant growth regulator in cotton cultivation, which can promote the assimilates to transfer to bolls. Nevertheless, the mechanism is still unclear. In this study, the weight of cotton bolls was found to increase significantly from 6 to 15 d after MC treatment, with a higher proportion of the increased dry matter being distributed to fibers compared to other parts of the boll. The ABA content, sucrose synthase and acid invertase activities in fibers increased significantly after MC treatment. The transcriptome, exogenous ABA spraying and VIGS experiments confirmed that the increase of ABA content in fibers was due to the up-regulation of biosynthetic genes GhNCED1A , GhNCED1B , and GhVP14 after MC treatment. The increased ABA induced the expression of genes encoding acid invertase and sucrose synthase, which ultimately accelerated the decomposition and transport of sucrose in the fibers, resulting in more glucose and fructose to enhance the cellulose synthesis and increase the boll weight. • MC treatment upregulated the expression of NCED genes resulting in ABA increase. • ABA positively induced the activity of sucrose synthase and acid invertase. • Accelerated decomposition and transport of sucrose enhanced the cellulose synthesis.