In fruit trees, flowering is a key event followed by fruit development and seed production. Gigentea ( GI ), a clock-associated gene, is known to contribute to photoperiodic flowering and circadian clock control in Arabidopsis thaliana . However, its functions in woody fruit trees remain unclear. In this study, a 2000 bp promoter fragment of the longan ( Dimocarpous longan ) DlGI gene was isolated from the genomic DNA of longan ‘Honghezi’ by polymerase chain reaction amplification. The DlGI promoter contained two main types of potential cis -acting elements: light-responsive and hormone-responsive elements. The promoter was fused with the β-glucuronidase ( GUS ) reporter gene of pBI121 to generate the pDlGI:GUS construct. GUS histochemical staining of transgenic A. thaliana revealed that DlGI might play a role in different developmental phases of longan. Exposure of transgenic A. thaliana to varying light intensities showed that the GUS activity increases with increased light intensity. Transient expression of pDlGI::GUS in Nicotiana benthamiana showed that the GUS activity was higher and reached peak a few hours earlier under short-day (SD) than long-day conditions. Exposure to different hormonal treatments revealed that the transcript level of GUS was activated by gibberellin (GA 3 ) and indoleacetic acid (IAA) but suppressed by abscisic acid and methyl jasmonate treatment. In addition, N. benthamiana transient assay and dual-luciferase assay revealed that the presence of early flowering 4 ( ELF4 ) homologs of longan ( DlELF4-1 and DlELF4-2 ) significantly activated the DlGI promoter. The positive response of DlGI promoter to high light-intensity, SD photoperiod, GA 3 and IAA signals, and DlELF4 transcription factor suggest that DlGI may function as a circadian clock and play a role in responding to SD conditions and other signals in flower initiation of longan.