Cloning and characterization of a novel chalcone synthase gene from Phalaenopsis hybrida orchid flowers

Abstract

Chalcone synthase (CHS, EC 2.3.1.74) is the key enzyme involved in flavonoid and anthocyanin biosynthesis. A complete DNA sequence of chalcone synthase gene designated Pchs1 was isolated by means of usual and then inverse polymerase chain reactions from genomic DNA of an orchid, Phalaenopsis hybrida , cv. Formosa rose. Nucleotide sequence analysis based on alignment with published Phalaenopsis chs cDNA revealed that Pchs1 contained an intact open reading frame of 1173-bp with one 109-bp intron at the conserved site. The deduced polypeptide (PCHS1) from Pchs1 comprised 390 amino acids with a predicted mol wt of 42.5 kD. PCHS1 showed 61–65% identities with CHS from other plants and retained most of the conserved residues. Some putative cis -regulatory elements were present at the 5′ and 3′ flanking regions of Pchs1 . Southern blot analysis predicted at least four chs -like genes, thus indicating the presence of a small multigene chs family in P. hybrida . Relative quantitative RT-PCR showed that Pchs1 is expressed in petals at early flower development as well as in lip tissue when the flower has just opened.