Interdisciplinary Center for Crop Plant Research (IZN), Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
Planta. 2010 Jun;232(1):19-35. doi: 10.1007/s00425-010-1168-z. Epub 2010 Apr 29.
Brassicaceous plants are characterized by a pronounced metabolic flux toward sinapate, produced by the shikimate/phenylpropanoid pathway, which is converted into a broad spectrum of O-ester conjugates. The abundant sinapate esters in Brassica napus and Arabidopsis thaliana reflect a well-known metabolic network, including UDP-glucose:sinapate glucosyltransferase (SGT), sinapoylglucose:choline sinapoyltransferase (SCT), sinapoylglucose:L-malate sinapoyltransferase (SMT) and sinapoylcholine (sinapine) esterase (SCE). 1-O-Sinapoylglucose, produced by SGT during seed development, is converted to sinapine by SCT and hydrolyzed by SCE in germinating seeds. The released sinapate feeds via sinapoylglucose into the biosynthesis of sinapoylmalate in the seedlings catalyzed by SMT. Sinapoylmalate is involved in protecting the leaves against the deleterious effects of UV-B radiation. Sinapine might function as storage vehicle for ready supply of choline for phosphatidylcholine biosynthesis in young seedlings. The antinutritive character of sinapine and related sinapate esters hamper the use of the valuable seed protein of the oilseed crop B. napus for animal feed and human nutrition. Due to limited variation in seed sinapine content within the assortment of B. napus cultivars, low sinapine lines cannot be generated by conventional breeding giving rise to genetic engineering of sinapate ester metabolism as a promising means. In this article we review the progress made throughout the last decade in identification of genes involved in sinapate ester metabolism and characterization of the encoded enzymes. Based on gene structures and enzyme recruitment, evolution of sinapate ester metabolism is discussed. Strategies of targeted metabolic engineering, designed to generate low-sinapate ester lines of B. napus, are evaluated.
芸薹属植物的特征是通过莽草酸/苯丙烷途径产生的大量代谢物流向芥子酸，然后转化为广泛的 O-酯缀合物。油菜和拟南芥中丰富的芥子酸酯反映了一个众所周知的代谢网络，包括 UDP-葡萄糖：芥子酰葡萄糖基转移酶（SGT）、芥子酰葡萄糖：胆碱芥子酰转移酶（SCT）、芥子酰葡萄糖：L-苹果酸芥子酰转移酶（SMT）和芥子酰胆碱（芥子碱）酯酶（SCE）。SGT 在种子发育过程中产生 1-O-芥子酰葡萄糖，然后由 SCT 转化为芥子碱，并在发芽种子中由 SCE 水解。释放的芥子酸通过芥子酰葡萄糖进入幼苗中由 SMT 催化的芥子酰苹果酸生物合成。芥子酰苹果酸参与保护叶片免受 UV-B 辐射的有害影响。芥子碱可能作为储存载体，为幼苗中磷酯酰胆碱生物合成提供现成的胆碱。芥子碱和相关芥子酸酯的抗营养特性阻碍了油菜籽宝贵种子蛋白在动物饲料和人类营养中的应用。由于油菜品种中种子芥子碱含量的变异有限，因此无法通过常规育种产生低芥子碱系，这导致了芥子酸酯代谢的遗传工程作为一种有前途的手段。本文综述了过去十年中在鉴定参与芥子酸酯代谢的基因以及表征编码酶方面取得的进展。基于基因结构和酶募集，讨论了芥子酸酯代谢的进化。设计用于生成低芥子酸酯油菜系的靶向代谢工程策略进行了评估。
