Ji Hongying, Liu Dantong, Yang Zhenle
Key Lab of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Biotechnol Biofuels. 2021 Mar 2;14(1):54. doi: 10.1186/s13068-021-01909-x.
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.
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.
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.
黄菖蒲是一种独特的植物物种，其块茎干重中可积累高达35%的油脂，这可能是植物界块茎组织中观察到的最高水平。为深入了解导致黄菖蒲油脂高积累的分子机制，将黄菖蒲块茎发育过程中涉及碳代谢、脂肪酸合成、三酰甘油合成和三酰甘油储存的油脂生成途径的基因表达谱，与油积累较少的黄菖蒲最近亲缘种紫菖蒲进行了比较。
与紫菖蒲相比，黄菖蒲中的高油脂积累与质体RubisCO旁路以及苹果酸和丙酮酸代谢的特定关键酶、几乎所有脂肪酸合成酶和种子样油体蛋白的显著上调有关。然而，两种植物中脂肪酸合成碳前体的碳代谢总体转录本相当，三酰甘油合成的转录本相似。发现两个种子样主转录因子ABI3和WRI1表现出相似的转录模式，但在黄菖蒲中的表达水平分别比紫菖蒲高6.5倍和14.3倍。加权基因共表达网络分析表明，ABI3与WRI1和其他关键油脂相关基因存在强烈的转录协同作用。
这些结果表明，丙酮酸的可用性和质体中的脂肪酸合成，以及油体中的三酰甘油储存，而非内质网中的三酰甘油合成，是黄菖蒲块茎油脂高产的主要因素，ABI3很可能在调节油脂积累中起关键作用。本研究对于理解富含油脂块茎中控制碳向油脂生成分配的分子机制具有重要意义，并为通过遗传育种或代谢工程提高作物非种子组织中的油脂积累提供了有价值的参考。
