SSLNPSPIPSYOVSPSSSSYPSPTR），PEST motif（PTAATIPECDESDASTVDSGQ）and a carboxyl- terminal（C）（VKPWIGEKIHEVGLDDLELTLGNGKA）. A phylogenetic analysis of BZR1 genes indicated that MdBZR1 shared high homologous amino acid sequences with apple BZR1 gene annotated in National Center for Biotechnology Information（NCBI）database. The expression pattern of MdBZR1 gene in different tissues of M9 was characterized. Results indicated that MdBZR1 transcript was detected in shoot tip，leaf，root，xylem and phloem of main stem，and the highest level appeared in shoot tip. Exogenous brassinosteroid（BR）and auxin increased primary shoot length of M9as well as Pingyitiancha（Malus hupehensis）and significantly induced the expression of MdBZR1. Primary shoot length was also increased by GA treatment，while MdBZR1 was neither induced nor repressed by GA obviously. In addition，MdBZR1 exhibited higher expression level in Nagafu/MM106 and Nagafu/Nagafu than Nagafu/M9. These results suggest that MdBZR1 may be involved in the regulation of apple tree size.