College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China.
Gene. 2013 Sep 15;527(1):266-74. doi: 10.1016/j.gene.2013.05.076. Epub 2013 Jun 11.
Xanthoceras sorbifolia is an excellent model system for studying triacylglycerol (TAG) biosynthesis in woody oilseed plants due to the high amount of seed oil, which is important for food and industrial uses. TAG is the major form of stored lipids in seeds and diacylglycerol acyltransferase (DGAT; EC 2. 3. 1. 20) catalyzes the final and critical step of TAG synthesis. Here, two novel DGAT genes, designated XsDGAT1 and XsDGAT2, were cloned from developing X. sorbifolia embryos. Sequence analysis showed that XsDGAT1 had little sequence homology to XsDGAT2. Heterologous expression of XsDGAT1 and XsDGAT2 in TAG-deficient yeast mutants restored TAG synthesis, confirming their biological activity. Expression of the two genes in wild-type Arabidopsis led to TAG synthesis and an increase in total seed oil in transgenic plants, with XsDGAT1 appearing to contribute to TAG synthesis at a greater level. Comparison of the expression patterns revealed that both XsDGAT1 and XsDGAT2 were expressed in the examined tissues and had similar spatiotemporal expression patterns with higher expression in embryos than in leaves and petals. The expression patterns of both XsDGAT1 and XsDGAT2 correlated with oil accumulation in developing X. sorbifolia embryos. These data suggest that XsDGAT1 and XsDGAT2 are both responsible for TAG synthesis in X. sorbifolia seeds.
文冠果是研究木本油料植物三酰基甘油(TAG)生物合成的极好模式系统，因为其种子油含量高，这对于食品和工业用途很重要。TAG 是种子中储存脂质的主要形式，二酰基甘油酰基转移酶(DGAT; EC 2.3.1.20)催化 TAG 合成的最后和关键步骤。在这里，从发育中的文冠果胚胎中克隆了两个新的 DGAT 基因，命名为 XsDGAT1 和 XsDGAT2。序列分析表明，XsDGAT1 与 XsDGAT2 的序列同源性很小。XsDGAT1 和 XsDGAT2 在 TAG 缺陷酵母突变体中的异源表达恢复了 TAG 合成，证实了它们的生物活性。这两个基因在野生型拟南芥中的表达导致了 TAG 合成和转基因植物中总种子油的增加，其中 XsDGAT1 似乎在更大程度上有助于 TAG 合成。表达模式的比较表明，XsDGAT1 和 XsDGAT2 都在检查的组织中表达，并且具有相似的时空表达模式，在胚胎中的表达高于在叶片和花瓣中的表达。XsDGAT1 和 XsDGAT2 的表达模式与发育中文冠果胚胎中的油脂积累相关。这些数据表明，XsDGAT1 和 XsDGAT2 都负责文冠果种子中的 TAG 合成。
