Feedback regulation of plastidic acetyl-CoA carboxylase by 18:1-acyl carrier protein in Brassica napus
Feedback regulation of plastidic acetyl-CoA carboxylase by 18:1-acyl carrier protein in Brassica napus
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DOI：
10.1073/pnas.1204604109
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发表时间：
2012-06-19
影响因子：
11.1
通讯作者：
Shanklin, John
中科院分区：
文献类型：
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作者：
Andre, Carl;Haslam, Richard P.;Shanklin, John
植物种子油代表了还原碳的主要可再生来源，但对其合成的生化调节知之甚少。本研究的目的是确定潜在的反馈调控的脂肪酸生物合成的甘蓝型油菜胚源细胞培养物和表征的反馈信号和酶的抑制目标。通过吐温酯递送的脂肪酸以剂量依赖性和可逆的方式迅速降低脂肪酸合成速率，表明在油积累组织中存在反馈抑制。吐温喂养不影响脂肪酸在胞质溶胶中的延伸或放射性标记的丙二酸纳入新生脂肪酸，这一起查明质体乙酰辅酶A羧化酶（ACCase）作为反馈抑制的酶靶。为了确定负责反馈的信号，测试了各种吐温酯对脂肪酸合成速率的影响。在喂食油酸（18：1）吐温酯后达到最大抑制，导致18：1游离脂肪酸、18：1-CoA和18：1-酰基载体蛋白（ACP）的细胞内蓄积。在培养物提取物和补充有生理浓度的18：1-ACP的发育中的油菜籽的提取物中观察到ACC酶活性的直接的、可饱和的抑制。提出了一种反馈抑制机制，其中对从头脂肪酸的需求减少导致18：1-ACP的积累，其直接抑制质体ACC酶，导致脂肪酸合成减少。定义这种机制为减轻作物中脂肪酸合成的反馈抑制以增加油产量提供了机会。
Plant seed oil represents a major renewable source of reduced carbon, but little is known about the biochemical regulation of its synthesis. The goal of this research was to identify potential feedback regulation of fatty acid biosynthesis in Brassica napus embryo-derived cell cultures and to characterize both the feedback signals and enzymatic targets of the inhibition. Fatty acids delivered via Tween esters rapidly reduced the rate of fatty acid synthesis in a dose-dependent and reversible manner, demonstrating the existence of feedback inhibition in an oil-accumulating tissue. Tween feeding did not affect fatty acid elongation in the cytosol or the incorporation of radiolabeled malonate into nascent fatty acids, which together pinpoint plastidic acetyl-CoA carboxylase (ACCase) as the enzymatic target of feedback inhibition. To identify the signal responsible for feedback, a variety of Tween esters were tested for their effects on the rate of fatty acid synthesis. Maximum inhibition was achieved upon feeding oleic acid (18:1) Tween esters that resulted in the intracellular accumulation of 18:1 free fatty acid, 18:1-CoA, and 18:1-acyl-carrier protein (ACP). Direct, saturable inhibition of ACCase enzyme activity was observed in culture extracts and in extracts of developing canola seeds supplemented with 18:1-ACP at physiological concentrations. A mechanism for feedback inhibition is proposed in which reduced demand for de novo fatty acids results in the accumulation of 18:1-ACP, which directly inhibits plastidic ACCase, leading to reduced fatty acid synthesis. Defining this mechanism presents an opportunity for mitigating feedback inhibition of fatty acid synthesis in crop plants to increase oil yield.