In order to isolate genes and their promoters in rice,we created a promoter trap system containing the promoterless β-glucuronidase (GUS) reporter gene in the T-DNA region.113^# was further analysisied,in which the GUS reporter gene was expressed constitutively.A single copy of the T-DNA was inserted into the plant genome,and the flanking sequence around T-DNA was isolated by inverse PCR.Sequencing and BLAST analyses suggested the T-DNA was inserted reversely in a candidate gene of rice chromosome 4.The promoter of the candidate gene directed GUS expression constitutively,analogous to the GUS expression pattern observed in 113^#.The results confirmed that the candidate gene was trapped by T-DNA (GUS) structure.