Different expression genes in the dedifferentiation progress with Affymetrix chips were analyzed.(1)According to data of the chips,there are 4 222 different expression genes,1 684 of them are up-regulated expression and 2 538 genes are down-regulated.(2)The genes relation to cell dedifferentiation according the data of chip and semi-qualitative RT-PCR were further identified and screened,and SMB (SOMBRERO) gene was firstly isolated.(3)SMB gene expression pattern was analyzed with real-time PCR.The gene expression level of SMB increased gradually with the time undergoing cell dedifferentiation.(4)The function of SMB gene undergoing plant cell dedifferentiation was further demonstrated.Test and verify mutant SMB gene in Arabidopsis can affect the procession of cell dedifferentiation and the ability of forming callus.This research demonstrated that SMB gene involves in cell dedifferentiation of Arabidopsis thaliana.