A heteromeric plastidic pyruvate kinase complex involved in seed oil biosynthesis in Arabidopsis
A heteromeric plastidic pyruvate kinase complex involved in seed oil biosynthesis in Arabidopsis
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DOI：
10.1105/tpc.106.048629
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发表时间：
2007-06-01
期刊：
影响因子：
11.6
通讯作者：
Benning, Christoph
中科院分区：
文献类型：
--
作者：
Andre, Carl;Froehlich, John E.;Benning, Christoph
糖酵解是一种普遍存在的途径，被认为是拟南芥种子和油料作物发育中产油所必需的。胚胎发育中初级代谢的区隔对检验这一假说和种子生物量生产的工程提出了重大挑战。这也引发了这样一个问题：在胚胎中，是否存在从进口光合作用到种子油的碳的首选途径。胞浆型丙酮酸激酶催化糖酵解的高度调节的、产生ATP的反应。拟南芥基因组编码14种可能的丙酮酸激酶亚型。有三个基因编码可塑性丙酮酸激酶的a、β(1)和β(2)亚单位。在发育中的种子中普遍存在的叶绿体酶可能含有4α4β(1)的亚基组成，在pH 8.0时最活跃，并被Glu抑制。破坏编码b1亚基的基因会导致可塑性丙酮酸激酶活性降低，种子含油量减少60%。通过b1亚基编码基因的表达和b2亚基编码基因的部分表达，可以完全恢复种子油的表型。因此，已鉴定的丙酮酸激酶催化了光合作用产物转化为石油的关键步骤，暗示了从底物磷酸烯醇式丙酮酸到脂肪酸的一条首选的质体途径。
Glycolysis is a ubiquitous pathway thought to be essential for the production of oil in developing seeds of Arabidopsis thaliana and oil crops. Compartmentation of primary metabolism in developing embryos poses a significant challenge for testing this hypothesis and for the engineering of seed biomass production. It also raises the question whether there is a preferred route of carbon from imported photosynthate to seed oil in the embryo. Plastidic pyruvate kinase catalyzes a highly regulated, ATP-producing reaction of glycolysis. The Arabidopsis genome encodes 14 putative isoforms of pyruvate kinases. Three genes encode subunits a, beta(1), and beta(2) of plastidic pyruvate kinase. The plastid enzyme prevalent in developing seeds likely has a subunit composition of 4 alpha 4 beta(1), is most active at pH 8.0, and is inhibited by Glu. Disruption of the gene encoding the b1 subunit causes a reduction in plastidic pyruvate kinase activity and 60% reduction in seed oil content. The seed oil phenotype is fully restored by expression of the b1 subunit-encoding cDNA and partially by the b2 subunit-encoding cDNA. Therefore, the identified pyruvate kinase catalyzes a crucial step in the conversion of photosynthate into oil, suggesting a preferred plastid route from its substrate phosphoenolpyruvate to fatty acids.