背景:黄色坚果是一种独特的植物物种,可以积累高达35%的块茎干重的油,也许是植物界块茎组织中观察到的最高水平。为了深入了解导致黄色坚果中高油积累的分子机制,产油途径的基因表达谱涉及碳代谢,脂肪酸合成,三酰甘油的合成,块茎发育过程中三酰甘油的储存与紫色的nutsedge进行了比较,黄色坚果的最近亲,油积累较差。
结果:与紫色nutsedge相比,黄色坚果中的高油积累与质体RubisCO旁路的特定关键酶以及苹果酸和丙酮酸代谢的显着上调有关,几乎所有的脂肪酸合成酶,和种子状的油体蛋白。然而,在两个物种中,碳代谢向脂肪酸合成的碳前体的总体转录本具有可比性,而三酰基甘油合成的总体转录本相似。发现两个种子样主转录因子ABI3和WRI1显示相似的转录模式,但在黄色坚果中的表达水平比在紫色坚果中的高6.5倍和14.3倍,分别。加权基因共表达网络分析显示,ABI3与WRI1和其他关键的石油相关基因具有很强的转录协调性。
结论:这些结果暗示质体中丙酮酸的可利用性和脂肪酸的合成,随着三酰甘油在油体中的储存,而不是内质网中的三酰甘油合成,是导致黄色坚果块茎高产油的主要因素,和ABI3最有可能在调节石油积累中起关键作用。该研究对于理解富油块茎中控制碳分配向产油的分子机制具有重要意义,并为通过遗传育种或代谢工程增强作物非种子组织中的油脂积累提供了有价值的参考。
BACKGROUND: Yellow nutsedge is a unique plant species that can accumulate up to 35% oil of tuber dry weight, perhaps the highest level observed in the tuber tissues of plant kingdom. To gain insight into the molecular mechanism that leads to high oil accumulation in yellow nutsedge, gene expression profiles of oil production pathways involved carbon metabolism, fatty acid synthesis, triacylglycerol synthesis, and triacylglycerol storage during tuber development were compared with purple nutsedge, the closest relative of yellow nutsedge that is poor in oil accumulation.
RESULTS: Compared with purple nutsedge, high oil accumulation in yellow nutsedge was associated with significant up-regulation of specific key enzymes of plastidial RubisCO bypass as well as malate and pyruvate metabolism, almost all fatty acid synthesis enzymes, and seed-like oil-body proteins. However, overall transcripts for carbon metabolism toward carbon precursor for fatty acid synthesis were comparable and for triacylglycerol synthesis were similar in both species. Two seed-like master transcription factors ABI3 and WRI1 were found to display similar transcript patterns but were expressed at 6.5- and 14.3-fold higher levels in yellow nutsedge than in purple nutsedge, respectively. A weighted gene co-expression network analysis revealed that ABI3 was in strong transcriptional coordination with WRI1 and other key oil-related genes.
CONCLUSIONS: These results implied that pyruvate availability and fatty acid synthesis in plastid, along with triacylglycerol storage in oil bodies, rather than triacylglycerol synthesis in endoplasmic reticulum, are the major factors responsible for high oil production in tuber of yellow nutsedge, and ABI3 most likely plays a critical role in regulating oil accumulation. This study is of significance with regard to understanding the molecular mechanism controlling carbon partitioning toward oil production in oil-rich tuber and provides a valuable reference for enhancing oil accumulation in non-seed tissues of crops through genetic breeding or metabolic engineering.