Pyruvate dehydrogenase kinase (PDK) is a negative regulator of the mitochondrial pyruvate dehydrogenase complex (mtPDC), which plays a key role in intermediary metabolism.In this study, a 1,490-bp PDK in Brassica napus (BnPDK1) was isolated and cloned from Brassica cDNA library.BnPDK1 has an 1 104 open reading frame encoding 367 amino acids.Genomic DNA gel blot analysis result indicated that BnPDK1 is a multi-copy gene.RNA gel blot analysis and RNA in situ hybridization were used to determine the expression of BnPDK1 in different organs.BnPDK1 gene was ubiquitously expressed in almost all the tissues tested, having the highest expression in the stamen and the young silique.Over-expression of BnPDK1 in transgenic Arabidopsis lines would repress the PDC activity, and resulted in the decrease of seed oil content and leaf photosynthesis.These results implied that BnPDK1 was involved in the regulation of fatty acid biosynthesis in developing seeds.