Li Teng, Sun Yan, Chen Ying, Gao Yu, Gao Huiling, Liu Baoling, Xue Jinai, Li Runzhi, Jia Xiaoyun
College of Agronomy/Institute of Molecular Agriculture and Bioenergy, Shanxi Agricultural University, Taigu, Shanxi 030801, China.
College of Agronomy/Institute of Molecular Agriculture and Bioenergy, Shanxi Agricultural University, Taigu, Shanxi 030801, China.
Plant Sci. 2022 Jun;319:111243. doi: 10.1016/j.plantsci.2022.111243. Epub 2022 Mar 9.
Cyperus esculentus is considered one of the most promising oil crops due to its oil-rich tuber, wide adaptability and large biomass production. Preferable triacylglycerol (TAG) composition, especially high oleic acid content, makes tuber oil suitable for human consumption and biodiesel production. However, the mechanism underlying oleic acid enrichment in the tuber remains unknown. Plastidial stearoyl-ACP desaturase (SAD) catalyses the formation of monounsaturated fatty acids (MUFAs), which may function crucially for high accumulation of oleic acid in C. esculentus tubers. In this study, two full-length cDNAs encoding SAD were isolated from the developing tubers of C. esculentus, namely, CeSAD1 and CeSAD2, with ORFs of 1194 bp and 1161 bp, respectively. Quantitative RT-PCR analysis showed that CeSAD genes were highly expressed in tubers. The expression pattern during tuber formation was also significantly correlated with fatty acid and oil accumulation dynamics. Overexpression of each CeSAD gene could restore the normal growth of the defective yeast BY4389, indicating that both CeSADs had fatty acid desaturase activity to catalyse MUFA biosynthesis. A tobacco genetic transformation assay demonstrated that both CeSAD enzymes had high enzyme activity. Exogenous addition of exogenous fatty acids to feed yeast revealed that CeSAD1 has a more substantial substrate preference ratio for C18:0 than CeSAD2 did. Moreover, the overexpression of CeSAD1 significantly increased host tolerance against low-temperature stress. Our data add new insights into the deep elucidation of oleic acid-enriched oils in Cyperus esculentus tubers, showing CeSAD, especially CeSAD1, as the target gene in genetic modification to increase oil and oleic yields in oil crops as well as stress tolerance.
由于其富含油脂的块茎、广泛的适应性和大量的生物量生产，油莎豆被认为是最有前途的油料作物之一。其适宜的三酰甘油（TAG）组成，尤其是高油酸含量，使得块茎油适合人类食用和生物柴油生产。然而，块茎中油酸富集的潜在机制仍不清楚。质体硬脂酰-ACP去饱和酶（SAD）催化单不饱和脂肪酸（MUFAs）的形成，这可能对油莎豆块茎中油酸的高积累起着关键作用。在本研究中，从油莎豆发育中的块茎中分离出两个编码SAD的全长cDNA，即CeSAD1和CeSAD2，其开放阅读框分别为1194 bp和1161 bp。定量RT-PCR分析表明，CeSAD基因在块茎中高度表达。块茎形成过程中的表达模式也与脂肪酸和油脂积累动态显著相关。每个CeSAD基因的过表达都能恢复缺陷酵母BY4389的正常生长，表明这两种CeSAD都具有脂肪酸去饱和酶活性，可催化MUFA生物合成。烟草遗传转化试验表明，这两种CeSAD酶都具有较高的酶活性。向酵母中添加外源脂肪酸进行喂养实验表明，与CeSAD2相比，CeSAD1对C18:0具有更高的底物偏好率。此外，CeSAD1的过表达显著提高了宿主对低温胁迫的耐受性。我们的数据为深入阐明油莎豆块茎中富含油酸的油脂提供了新的见解，表明CeSAD，尤其是CeSAD1，作为基因改造的目标基因，可提高油料作物的油脂和油酸产量以及胁迫耐受性。
