Transgenic Modification of Acetyl CoA Carboxylase and ß-Keto Reductase Levels in Brassica Napus Functional and Regulatory Analysis

Abstract

In plants de novo fatty acid biosynthesis occurs within the plastids. The first committed step in this process is the ATP dependant carboxylation of acetyl CoA to malonyl CoA. This is catalysed by acetyl CoA carboxylase (ACCase, EC 6.4.1.2), which is believed to be a key regulatory enzyme in this process (Post Beittenmiller et al. 1992). Two forms of ACCase have now been identified in dicots. A single large multifunctional polypeptide (ACCase I), and a multipeptide prokaryotic form (ACCase II). Subcellular localisation studies on ACCase II (Alban et al. 1995; Shorrosh et al. 1995; Elborough et al. 1996) indicate a chloroplast localisation. This is suggestive of a role in de novo fatty acid biosynthesis. The extrachloroplastic localisation (Alban et al 1994) of ACCase I suggests a different role. ACCase I is responsive to UV and fungal elicitors possibly indicating a role in cytosolic fatty acid elongation, and wax and flavanoid biosynthesis.