title: Targeting of the polyhydroxybutyrate biosynthetic pathway to the plastids of Arabidopsis thaliana results in high levels of polymer accumulation.
abstract: In the bacterium Alcaligenes eutrophus, three genes encode the enzymes necessary to catalyze the synthesis of poly[(R)-(-)-3-hydroxybutyrate] (PHB) from acetyl-CoA. In order to target these enzymes into the plastids of higher plants, the genes were modified by addition of DNA fragments encoding a pea chloroplast transit peptide, a constitutive plant promoter, and a poly(A) addition sequence. Each of the modified bacterial genes was introduced into Arabidopsis thaliana by Agrobacterium-mediated transformation, and plants containing all three genes were obtained by sexual crosses. These plants accumulated PHB up to 14% of the dry weight as 0.2- to 0.7-micron granules within plastids. In contrast to earlier experiments in which expression of the PHB biosynthetic pathway in the cytoplasm led to a deleterious effect on growth, expression of the PHB biosynthetic pathway in plastids had no obvious effect on the growth or fertility of the transgenic plants and resulted in a 100-fold increase in the amount of PHB that accumulated. We conclude that there does not appear to be any biological barrier to high-level production of PHB in higher plants. The high level of PHB accumulation also suggests that the synthesis of plastid acetyl-CoA is regulated by a mechanism which responds to metabolic demand.
authors: Department of Plant Biology, Carnegie Institution of Washington, Stanford, CA 94305.
authors: C
authors: C
authors: Nawrath
authors: Y
authors: Y
authors: Poirier
authors: C
authors: C
authors: Somerville
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis; D002451:Cell Compartmentation; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D018087:Plastids / Q000378:metabolism*; D011091:Polyesters / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D011091:Polyesters; D011994:Recombinant Proteins; D000445:Aldehyde Oxidoreductases; C027014:acetaldehyde dehydrogenase (acylating); D000217:Acyltransferases; C060970:poly-beta-hydroxybutyrate polymerase