CHARACTERIZATION OF GENES INVOLVED IN BIOSYNTHESIS OF CORONAFACIC ACID, THE POLYKETIDE COMPONENT OF THE PHYTOTOXIN CORONATINE

Coronafacic acid (CFA) is the polyketide component of coronatine (COR) , a phytotoxin produced by the plant pathogen, Pseudomonas syringae. I n the present study we have determined the nucleotide sequence of a 3. 92-kb DNA fragment involved in CFA biosynthesis. Analysis of the seque nce revealed four complete open reading frames (ORFs) designated cfa1 to cfa4 and one incomplete ORF (cfa5), all transcribed in the same dir ection. The predicted translation products of cfa1, cfa2 and cfa3 show ed relatedness to acyl carrier proteins, fatty acid dehydrases and bet a-ketoacylsynthases, respectively, which are required for polyketide s ynthesis. cfa1 was subcloned, its sequence was confirmed, and it was o verexpressed in E. coli to yield a peptide with an apparent molecular mass of 6 kDa.