Xing Shufan, van Deenen Nicole, Magliano Pasqualina, Frahm Lea, Forestier Edith, Nawrath Christiane, Schaller Hubert, Gronover Christian S, Prüfer Dirk, Poirier Yves
Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH-1015, Lausanne, Switzerland.
Plant J. 2014 Jul;79(2):270-84. doi: 10.1111/tpj.12559. Epub 2014 Jun 19.
Cytosolic acetyl-CoA is involved in the synthesis of a variety of compounds, including waxes, sterols and rubber, and is generated by the ATP citrate lyase (ACL). Plants over-expressing ACL were generated in an effort to understand the contribution of ACL activity to the carbon flux of acetyl-CoA to metabolic pathways occurring in the cytosol. Transgenic Arabidopsis plants synthesizing the polyester polyhydroxybutyrate (PHB) from cytosolic acetyl-CoA have reduced growth and wax content, consistent with a reduction in the availability of cytosolic acetyl-CoA to endogenous pathways. Increasing the ACL activity via the over-expression of the ACLA and ACLB subunits reversed the phenotypes associated with PHB synthesis while maintaining polymer synthesis. PHB production by itself was associated with an increase in ACL activity that occurred in the absence of changes in steady-state mRNA or protein level, indicating a post-translational regulation of ACL activity in response to sink strength. Over-expression of ACL in Arabidopsis was associated with a 30% increase in wax on stems, while over-expression of a chimeric homomeric ACL in the laticifer of roots of dandelion led to a four- and two-fold increase in rubber and triterpene content, respectively. Synthesis of PHB and over-expression of ACL also changed the amount of the cutin monomer octadecadien-1,18-dioic acid, revealing an unsuspected link between cytosolic acetyl-CoA and cutin biosynthesis. Together, these results reveal the complexity of ACL regulation and its central role in influencing the carbon flux to metabolic pathways using cytosolic acetyl-CoA, including wax and polyisoprenoids.
胞质乙酰辅酶A参与多种化合物的合成，包括蜡、甾醇和橡胶，由ATP柠檬酸裂解酶（ACL）产生。为了了解ACL活性对乙酰辅酶A碳通量向胞质中发生的代谢途径的贡献，人们培育了过表达ACL的植物。从胞质乙酰辅酶A合成聚酯聚羟基丁酸酯（PHB）的转基因拟南芥植物生长减缓且蜡含量降低，这与胞质乙酰辅酶A向内源途径的可用性降低一致。通过过表达ACLA和ACLB亚基来增加ACL活性，在维持聚合物合成的同时逆转了与PHB合成相关的表型。PHB自身的产生与ACL活性增加有关，这一增加发生在稳态mRNA或蛋白质水平没有变化的情况下，表明ACL活性存在响应库强度的翻译后调控。在拟南芥中过表达ACL与茎上蜡含量增加30%有关，而在蒲公英根的乳管中过表达嵌合同源ACL分别导致橡胶和三萜含量增加4倍和2倍。PHB的合成和ACL的过表达还改变了角质单体十八碳二烯 - 1,18 - 二酸的含量，揭示了胞质乙酰辅酶A与角质生物合成之间意想不到的联系。总之，这些结果揭示了ACL调控的复杂性及其在影响利用胞质乙酰辅酶A的代谢途径（包括蜡和聚异戊二烯）的碳通量方面的核心作用。
