Antisense expression and overexpression of biotin carboxylase in tobacco leaves.
The plastid acetyl-coenzyme A carboxylase (ACCase) catalyzes the first committed step of fatty acid synthesis and in most plants is present as a heteromeric complex of at least four different protein subunits: the biotin carboxylase (BC), the biotin carboxyl carrier protein, and the alpha and beta subunits of the carboxyltransferase. To gain insight into the subunit organization of this heteromeric enzyme complex and to further evaluate the role of ACCase in regulating fatty acid synthesis, BC expression was altered in transgenic plants. Tobacco (Nicotiana tabacum) was transformed with antisense-expression and overexpression tobacco BC constructs, which resulted in the generation of plants with BC levels ranging from 20 to 500% of wild-type levels. Tobacco plants containing elevated or moderate decreases in leaf BC were phenotypically indistinguishable from wild-type plants. However, plants with less than 25% of wild-type BC levels showed severely retarded growth when grown under low-light conditions and a 26% lower leaf fatty acid content than wild-type plants. A comparison of leaf BC and biotin carboxyl carrier protein levels in plants with elevated and decreased BC expression revealed that these two subunits of the plastid ACCase are not maintained in a strict stoichiometric ratio.
Shintani
D
D
Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, USA.
Roesler
K
K
Shorrosh
B
B
Savage
L
L
Ohlrogge
J
J
D000103:Acetyl-CoA Carboxylase / Q000096:biosynthesis; D019731:Carbon-Nitrogen Ligases; D002352:Carrier Proteins / Q000096:biosynthesis; D016373:DNA, Antisense; D018076:DNA, Complementary; D054889:Fatty Acid Synthase, Type II; D015870:Gene Expression; D015151:Immunoblotting; D008025:Ligases / Q000096:biosynthesis*; D008027:Light; D046911:Macromolecular Substances; D018515:Plant Leaves; D010947:Plants, Toxic; D018087:Plastids / Q000201:enzymology; D011994:Recombinant Proteins / Q000096:biosynthesis; D014026:Nicotiana / Q000201:enzymology* / Q000254:growth & development
D002352:Carrier Proteins; D016373:DNA, Antisense; D018076:DNA, Complementary; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D054889:Fatty Acid Synthase, Type II; D008025:Ligases; D019731:Carbon-Nitrogen Ligases; C019791:biotin carboxylase; D000103:Acetyl-CoA Carboxylase; C079633:biotin carboxyl carrier protein