Cloning of the DenACS from Dendrobium hybrid cultivar Anna was performed by RT-PCR and nucleotide sequence analysis revealed that the open reading frame of this gene was 1,308 bp in length, encoded for a protein of 435 amino acid residues. The calculated molecular mass of the deduced polypeptide is 48.5 kDa and the predicted isoelectric point is 5.84 The deduced amino acid sequence of the DenACS-encoded protein showed a high degree of identity to those of the ACS from petunia, geranium, carnation and rose. The expression of DenACS was examined by RT-PCR and the results revealed that this gene was highly expressed in flower stage 2 (partially opened flower) and stage 3 (full opened flower) during flower development. It was also expressed in all floral tissues and organs including petal, sepal, pedicel, labellum, stigma, young leaves and roots, but the maximum expression was observed in petal, sepal and pedicel. These results indicated that the orchid DenACS is involved in the flower opening, flower senescence as well as in vegetative cell growth and development. © 2010 Academic Journals.