Cloning and characterization of a novel PI-like MADS-box gene in Phalaenopsis orchid.

The specification of floral organ identity during development depends on the function of a limited number of homeotic genes, which are grouped into three classes. Most of these genes belong to the MADS-box gene family. The PISTILLATA (PI) family of MADS-box genes plays important roles in controlling the development of the petal and stamen of flowering plants. In an attempt to understand the molecular mechanisms behind floral development in the orchid, a MADS-box gene, PhPI10 was cloned from Phalaenopsis orchid. We provide phylogenetic evidence that PhPI10 is closely related to PI-like genes of angiosperms, which are required for establishing petal and stamen identity. In addition, there is a PI-motif in the C-terminal of the putative amino acid sequence of PhPI10. Southern analysis showed that a single copy of PhPI10 was present in the Phalaenopsis orchid genome. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that its transcription was only detectable in the top of the floral bud and undetectable in other vegetative organs. In the floral organs its expression was limited to the lip of the Phalaenopsis flower.