Acetyl-CoA Carboxylase in Higher Plants: Most Plants Other Than Gramineae Have Both the Prokaryotic and the Eukaryotic Forms of This Enzyme

Abstract

The presence and the absence of a prokaryote type and a eukaryote type of acetyl-CoA carboxylase (EC 6.4.1.2; ACCase) were examined in members of 28 plant families by two distinct methods: the detection of biotinylated subunits of ACCase with a streptavidin probe, and the detection of the accD gene, which encodes a subunit of the prokaryotic ACCase, by Southern hybridization analysis. The protein extracts of all the plants studied contained a biotinylated polypeptide of 220 kDa, which was probably the eukaryotic ACCase. All the plants but those belonging to Gramineae also contained a biotinylated polypeptide of ca. 35 kDa, which is a putative subunit of the prokaryotic ACCase. In all plants but those in Gramineae, the ca. 35 kDa polypeptide was found in the protein extracts of plastids, while the 220 kDa polypeptide was absent from these plastid extracts. The plastid extracts of the plants in Gramineae contained the 220 kDa polypeptide, as did the homogenates of the leaves. Southern hybridization analysis demonstrated that all the plants but those in the Gramineae contained the accD gene. These findings suggest that most higher plants have the prokaryotic ACCase in the plastids and the eukaryotic ACCase in the cytosol. Only Gramineae plants might contain the eukaryotic ACCases both in the plastids and in the cytosol. The origin of the plastid-located eukaryotic ACCase in Gramineae is discussed as the first possible example of substitution of a plastid gene by a nuclear gene for a non-ribosomal component.

Hormonal and Stress Induction of the Gene Encoding Common Bean Acetyl-Coenzyme A Carboxylase

“…Most species have both forms with heteromeric enzymes in plastids and the homodimeric enzyme in the cytosol. In grasses, the homodimeric form is found in both the plastid and cytosol (Konishi and Sasaki, 1994;Konishi et al, 1996) and no heteromeric enzyme exists. Plastids of Brassica napus (Schulte et al, 1997) contain both a homodimeric and the expected heteromeric isoform.…”

“…Indeed, only the cytosolic form of ACCase, but not the chloroplastic isoform, is induced by UV-B irradiation. This response results in higher malonyl-CoA concentrations for flavonoid synthesis in the cytosol (Konishi et al, 1996). Flavonoids have also been implicated as endogenous negative regulators of polar auxin transport and are important phytoalexins in legumes (Dixon and Pavia, 1995).…”

An Isoleucine Residue within the Carboxyl-Transferase Domain of Multidomain Acetyl-Coenzyme A Carboxylase Is a Major Determinant of Sensitivity to Aryloxyphenoxypropionate But Not to Cyclohexanedione Inhibitors

“…This reaction is a two-step process, consisting of the ATP-dependent carboxylation of the biotin group on the carboxyl carrier domain by the biotin-carboxylase activity, followed by the transfer of the carboxyl group from biotin to acetyl-CoA by the carboxyl-transferase (CT) activity. In plants, two ACCase isoforms are found in the cytosol and in the chloroplast, respectively (Sasaki et al, 1995;Konishi et al, 1996). The cytosolic ACCase isoform in all plants studied so far is a multidomain enzyme.…”

Targeting of the Arabidopsis Homomeric Acetyl-Coenzyme A Carboxylase to Plastids of Rapeseeds

“…The heteromeric ACCase type, also referred to as the multisubunit or prokaryotic type, is present in plastids of dicotyledons and of non-Gramineae monocotyledons (Konishi et al, 1996). This ACCase type is composed of biotin carboxylase, biotin carboxyl carrier protein, and carboxyltransferase ci and p subunits.…”