Phosphoenolpyruvate carboxylase (PEPC) is a carbon-fixing enzyme with critical roles in seed development. Previously we observed a positive correlation between PEPC activity and protein content in mature seeds among soybean cultivars and varietal differences of PEPC activity in immature seeds, which is concordant with seed protein accumulation. Here, we report a PEPC isoform (Gmppc2) which is preferentially expressed in immature soybean seeds at the late maturation stage. Gmppc2 was co-expressed with enzyme genes involved in starch degradation: α-amylase, hexokinase, and α-glucan phosphorylase. Gmppc2 was developmentally induced in the external seed coats, internal seed coats, hypocotyls, and cotyledons at the late maturation stage. The expression of Gmppc2 protein was negatively regulated by the application of a nitrogen fertilizer, which suppressed nodule formation. These results imply that Gmppc2 is involved in the metabolism of nitrogen originated from nodules into seeds, and Gmppc2 might be applicable as a biomarker of seed protein content.Abbreviations: PEP: phosphoenolpyruvate; PEPC: phosphoenolpyruvate carboxylase; RNA-Seq: RNA sequencing; PCA: principal component analysis; SE: standard error.

中文翻译：

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植物型磷酸烯醇丙酮酸羧化酶 Gmppc2 在成熟后期的未成熟大豆种子中被诱导发育：种子化学成分的潜在蛋白质生物标志物。


磷酸烯醇丙酮酸羧化酶 (PEPC) 是一种固碳酶，在种子发育中发挥着关键作用。此前我们观察到大豆品种成熟种子中PEPC活性与蛋白质含量呈正相关，且未成熟种子中PEPC活性存在品种差异，这与种子蛋白质积累一致。在这里，我们报道了一种 PEPC 同工型 (Gmppc2)，它优先在成熟后期的未成熟大豆种子中表达。 Gmppc2 与参与淀粉降解的酶基因共表达：α-淀粉酶、己糖激酶和 α-葡聚糖磷酸化酶。 Gmppc2 在成熟后期在外部种皮、内部种皮、下胚轴和子叶中被诱导发育。 Gmppc2 蛋白的表达受到氮肥施用的负调节，从而抑制了根瘤的形成。这些结果表明Gmppc2参与来自根瘤的氮代谢进入种子，并且Gmppc2可能适用于种子蛋白质含量的生物标志物。 PEPC：磷酸烯醇丙酮酸羧化酶； RNA-Seq：RNA测序； PCA：主成分分析； SE：标准错误。