The Functional Expression of the CHS-D and CHS-E Genes of the Common Morning Glory (Ipomoea purpurea) in Escherichia coli and Characterization of Their Gene Products

The genes encoding chalcone synthase (CHS) in the common morning glory (Ipomoea purpurea) comprise a multigene family, and they are divided into two subfamilies. The genes in a subfamily including the CHS-A, CHS-B and CHS-C genes are distantly related to the other known CHS sequences in a phylogenetic tree, whereas the CHS-D and CHS-E genes in another subfamily are more closely related to the well-characterized CHS genes.As an initial step to elucidate biological function of these CHS genes in I. purpurea, the CHS-D and CHS-E cDNAs were expressed in Escherichia coli with different expression systems. The recombinant CHS-D and CHS-E proteins both showed CHS activity to produce naringenin chalcone. These results are discussed with regard to the biological roles of the CHS-D and CHS-E genes in flower pigmentation in I. purpurea. We have also discussed these CHS-D and CHS-E enzyme as members of plant specific polyketide synthases.