Mechanism of the Mixture of Abscisic Acid and Thidiazuron in Regulating Cotton Leaf Abscission

Morphological analysis and RNA-seq were conducted to profile the differentially expressed genes (DEGs) at different time points after treatment with a mixture of ABA and TDZ (AT), a mixture of TDZ and diuron (TD), ABA (A), TDZ (T), or water (W). A total of 2805 DEGs were detected after treatment with A, 18 849 DEGs after treatment with T, 29 822 DEGs after treatment with AT, and 26 446 DEGs after treatment with TD. GO and KEGG analyses revealed the enrichment of functional categories, including plant hormone signal transduction and metabolic pathways, after AT treatment. Ethylene-related genes (ACO3 and ACS) and cytokinin oxidase/dehydrogenase (CKX) were upregulated. Cytokinin response regulatory factors (ARRs) were downregulated, and the cytokinin content was decreased. Gibberellin-related genes (GIDs) were downregulated, and jasmonic-acid-related genes (JAZ10) were upregulated. The results showed that the interaction between ethylene and CTK regulated cotton leaf defoliation after AT treatment. Significantly, gibberellin and jasmonic acid also played a role in cotton leaf defoliation. The results of this study lay a foundation for further exploration of the function of ABA and TDZ in regulating cotton defoliation.