Abstract: Afull-length 958 bp cDNA of AP1（APETALA1）-like was obtained by RT-PCR and RACE amplification the total RNA extracted from the scapes of Oncidium‘Gower Ramsey’（Orchidaceae）at flowering stage. The gene consisted of 690 bp gene encoding region which encoding a protein of 229 amino acids，was designated as OnAP1-like（accession number：KC426946）. The analysis of secondary structure of protein showed that the protein was hydrophilic，and it contained 48.91% of α-helix，10.92% of β-sheet and 40.17% of random coil. The analysis of protein sequence alignment and cluster showed that the OnAP1-like was close to AP1-like of Cymbidium faberi with an overall sequence similarity. Using RT-qPCR to analysis the expression quantity of OnAP1-like of different organsfrom Oncidium in different stages，the results showed that in different development stages，the expression level of leaves was the highest in flower budding stage，that of root and scapes gradually increased with development and obtained the highest expression level at post-flowering stage. In different organs，the expression level of roots was higher than that of leaves before reproductive growth stage；The expression level of petals was the highest in flower budding stage，and that of scapes was the highest in flowering and post-flowering stage. The results suggest that OnAP1-like gene play a significant role in the development and formation of flowers in Oncidium‘Gower Ramsey’.

Key words: Oncidium, MADS-box gene AP1-like, RT-qPCR, clone, expression analysis