Abstract: Arabidopsis CRY1 (cryptochrome 1) protein initiates blue light signal transduction in a protein interaction manner, consequently causes the photomorphogenesis in plants. To further study the mechanism of CRY1 mediating blue light signal transduction, CRY1 was used as a bait, the methods of yeast two hybrid system, such as preliminary auxotrophy, liquid assays and domain interactions analyses in yeast cells were employed to screen the transcription factor proteins from the Arabidopsis transcription factor yeast library. The results showed that 41 transcription factor proteins were screened out by the preliminary auxotrophy and the liquid assays with ONPG as substrate; the transcription factor proteins which interacted with CRY1 with high blue light dependent or strong enzyme activity were picked out for a further validation using liquid assay with CPRG as substrate, and found that their interactions with CRY1 showed blue light dependent and the activity of interactions would increase with the time of blue light treatment; the interactions analyses results of CRY1 domains and transcription factor protein showed that the transcription factor proteins SPL3 and IDD4 interacted with the N terminus of CRY1 primarily, and relatively weak with the C terminus, however, the blue light dependent existed between the interaction of the C terminus of CRY1 and SPL3, but not so obvious with IDD4

Key words: CRY1, yeast two-hybrid system, transcription factors, Arabidopsis thaliana