Expression and Function of Aromatic PolyketideSynthase Genes in Raspberries (Rubus idaeus sp.)

摘要

The genus Rubus contains a family of type III polyketidesynthases which show differences in structure and function.We have cloned and characterized five aromatic polyketidesynthase genes from raspberries. All five genes contain anintron of varying length and have 1173 bp coding sequences,with the exception of one gene that consists of 1149 bp. Fourof the five genes encode proteins with 391 amino acid residueswith a calculated protein mass of 42 kDa, while one genecoded for a shorter protein consisting of 383 amino acids.Sequence comparison of the five polyketide synthase genesshowed high similarity both at the DNA and protein levels.Differences in the coding region were found mainly in theflanking sequences. Analysis of the reaction products showedthat PKS 1 and PKS5 were chalcone synthases, PKS2 thatdiffers in six amino acids from PKS I is silent, PKS3 is ap-coumarate triacetic acid lactone synthase (CTAS) and PKS4is a benzalacetone synthase (BAS). The structural variationsand the architecture of these PKS genes and enzymes isdiscussed.