Isolation and phylogenetic footprinting analysis of the promoter region of the floral homeotic gene OrcPI from Orchis italica (Orchidaceae)

The nucleotide sequences of regulatory elements from homologous genes can be strongly divergent. Phylogenetic footprinting, a comparative analysis of noncoding regions, can detect putative transcription factor binding sites (TFBSs) shared among the regulatory regions of 2 or more homologous genes. These conserved motifs have the potential to serve the same regulatory function in distantly related taxa. We isolated the 5'-noncoding region of the OrcPI gene, a MADS-box transcription factor involved in flower development in Orchis italica, using the thermal asymmetric interlaced polymerase chain reaction technique. This region (comprising 1352 bp) induced transient beta-glucuronidase expression in the petal tissue of white Rosa hybrida flowers and represents the 5'-regulatory sequence of the OrcPI gene. Phylogenetic footprinting analysis detected conserved regions within the 5'-regulatory sequence of OrcPI and the homologous regions of Oryza sativa, Lilium regale, and Arabidopsis thaliana. Some of these sequences are known TFBSs described in databases of plant regulatory elements. Nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the following accession numbers: AF198055 promoter region of the PISTILLATA (PI) gene of A. thaliana; AB094985 cDNA of OrcPI (PI/GLOBOSA [PI/GLO] homologue) of O. italica; AB378089 5'-regulatory region of the OrcPI gene of O. italica; AP008211 putative promoter region of OSMADS2 (PI/GLO homologue) of O. sativa; AP008207 putative promoter region of OSMADS4 (PI/GLO homologue) of O. sativa; and AB158292 putative promoter region of the PI/GLO homologue of L. regale.