Characterization and Activity Analyses of the Promoter in

Flowering transition is a crucial development process in cotton ( L.), and the flowering time is closely correlated with the timing of () expression. However, the mechanism underlying the coordination of various -regulatory elements in the promoter of cotton has not been determined. In this study, a 5.9-kb promoter of was identified from cotton. A bioinformatics analysis showed that multiple insertion-deletion sites existed in the 5.9-kb promoter. Different expression levels of a reporter gene, and the induction by sequential deletions in promoter, demonstrated that 1.8-kb of the promoter was stronger than 4.2-, 4.8-, and 5.9-kb promoter fragments. The binding sites of the CONSTANS (CO) and NUCLEAR FACTOR Y transcription factors were located within the 1.0-kb sequence upstream of the transcription start site. A large number of repeat segments were identified in proximal promoter regions (-1.1 to -1.4 kb). A complementation analysis of deletion constructs between 1.0 and 1.8 kb of , , and promoters revealed that the 1.0-kb fragment significantly rescued the late-flowering phenotype of the loss-of-function mutant , whereas the 1.8-kb promoter only slightly rescued the late-flowering phenotype. Furthermore, the conserved CORE motif in the cotton promoter is an atypical TGTG(N2-3)ATG, but the number of arbitrary bases between TGTG and ATG is uncertain. Thus, the proximal promoter region might play an important role affecting the activity levels of promoters in cotton flowering.