Abstract: Protocorm-like bodies（PLBs）is a new protocol of efficient regeneration，and the development of rhizoids is a critical stage of PLB regeneration. Recent researches showed that cytokinin regulated the formation of rhizoids. Here，we isolated the full length cDNA of a gene encoding cytokinin dehydrogenase from rhizoids of Rosa canina，named RcCKX5. Sequence analysis indicated that RcCKX5 consisted of 1 815 bp，with ORF of 1 626 bp，5′ UTR of 104 bp，3′ UTR of 85 bp，encoded 541 amino acids. The deduced amino acids possessed conserved domains of CKX family，FAD-binding domain and cytokinin-bining domain. Multiple sequence alignments and phylogenetic analysis showed that RcCKX5 had the highest similarity with TcCKX5 from Theobroma cacao. Real-time PCR analysis indicated that expression level of RcCKX5 in root was the highest，and expression level in flower and fruit was high.Expression level of RcCKX5 keep increasing all along the formation of rhizoids，reached the highest peak in the twenty-first day，then decreased slightly. This indicated RcCKX5 might be involved in rhizoids formation. RcCKX5 was significantly and rapidly induced by 6-BA，expression level of RcCKX5 reached highest with the concentration of 2.5 mg ? L-1 and time of 120 h.

Key words: Rosa canina, rhizoid, cytokinin dehydrogenase, expression analysis