Antisense Expression of 3-Oxoacyl-ACP Reductase Affects Whole Plant Productivity and Causes Collateral Changes in Activity of Fatty Acid Synthase Components

Abstract

Brassica napus cv Westar plants were transformed with 3-oxoacyl-ACP reductase (KR) in antisense orientation, driven by either the cauliflower mosaic virus 35S promoter or a seed-specific acyl carrier protein promoter to determine the effects on plant productivity and on the activity of other fatty acid synthase (FAS) components. In plants with altered KR activity, total seed yield was reduced in all cases. In less severely affected plant lines, seeds had a normal appearance and composition but the yield of seeds was reduced by approximately 50%. In more severely affected lines, reductions in both seed fatty acid content and the number of seeds produced per plant were evident, resulting in a 90% reduction in fatty acid synthesized per plant. These phenotypes were independent of the promoter used. In severely affected lines, a large proportion of seeds showed precocious germination, and these had a reduced oleate content and increased levels of polyunsaturated 18-carbon fatty acids, compared with normal seeds of the same line. This reduction in 18:1 fatty acids was mimicked on imbibition of seeds with a normal appearance, indicating a preferential use of oleate moieties in precocious germination events. The reduction in activity of KR was mirrored for a second fatty acid synthase component, enoyl-ACP reductase, indicating a mechanism to maintain the ratio of fatty acid synthase components throughout embryogenesis.

Metabolic control analysis of developing oilseed rape (Brassica napus cv Westar) embryos shows that lipid assembly exerts significant control over oil accumulation

“…These conditions are typical of previous studies with oilseed rape embryos (e.g. O'Hara et al, 2007).…”

Transcriptome, Biochemical and Growth Responses of the Marine Phytoplankter Phaeodactylum Tricornutum Bohlin (Bacillariophyta) to Copepod Grazer Presence

“…9b), fabG (3-oxoacyl-ACP reductase) catalyzes the NADPH-dependent reduction of beta-ketoacyl-ACP substrates to beta-hydroxyacyl-ACP products, in the elongation cycle of fatty acid biosynthesis [94]. In a previous study, Brassica napus was transformed with fabG in anti-sense orientation, leading to 90% reduction in fatty acid synthesized per plant [95]. In this study, the down-regulation of the fabG gene, EC 1.14.19.2 (stearoyl-[acyl-carrier-protein] 9-desaturase) revealed the reduction of content and content variation of the fatty acids per cell (Fig.…”

Transparent Testa16Plays Multiple Roles in Plant Development and Is Involved in Lipid Synthesis and Embryo Development in Canola

“…The KAR enzyme catalyzes the first reduction step in FA biosynthesis (Harwood, 1988). O'Hara et al (2007) reported that antisense expression of the canola KAR gene results in reduced seed oil content and seed yield. BCCP1 is an essential subunit for a heteromeric acetylCoA carboxylase, which catalyzes the ATP-dependent formation of malonyl-CoA in the first committed step of the FA biosynthetic pathway (Ohlrogge and Browse, 1995).…”

“…The abnormal embryo development may be due, at least partly, to the decreased synthesis of storage oil, although we could not rule out other possibilities. Indeed, other studies have shown that some genes encoding components of FA synthesis play important roles in embryo and seed development in Arabidopsis and canola (O'Hara et al, 2007;Wu and Xue, 2010;Li et al, 2011).…”

“…For lipid metabolism, nine genes were downregulated and 18 genes were up-regulated. For example, 3-Oxoacyl-ACP reductase5 (KAR5) and Chloroplastic acetyl-coenzyme A carboxylase1 (BCCP1), both involved in FA synthesis, were down-regulated in RNAi plants (Table II; Harwood, 1988;O'Hara et al, 2007). For gynoecium and embryo development, 50 genes were down-regulated and 15 genes were up-regulated.…”