Identification of tung tree FATB as a promoter of 18:3 fatty acid accumulation through hydrolyzing 18:0-ACP
Identification of tung tree FATB as a promoter of 18:3 fatty acid accumulation through hydrolyzing 18:0-ACP
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通过水解18:0-ACP鉴定油桐FATB作为18:3脂肪酸积累的促进剂
DOI：
10.1007/s11240-020-01998-w
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发表时间：
2021-01-27
影响因子：
3
通讯作者：
Pei, Ying
中科院分区：
文献类型：
--
作者：
Chen, Hao;Zhang, Fuhao;Pei, Ying
关键信息VfFATB在叶绿体中的功能。VfFATB表达水平与桐油含量呈正相关。VfFATB是植物正常发育所必需的。VfFATB是一种18：0-ACP型硫酯酶，从油桐种子中提取的桐油具有良好的干燥特性，具有重要的工业应用价值。先前的比较转录组分析表明，一个假定的油桐脂肪酸B基因（VfFAT B）编码脂肪酰基-ACP（酰基载体蛋白）硫酯酶B（FAT B）在油合成阶段显著不受调控。脂肪酰基-ACP硫酯酶通过从酰基-ACP释放酰基链来决定脂肪酸碳链的长度。为了更好地了解桐酸生物合成的机制，需要进一步研究油桐种子中参与脂肪酸合成途径的VfFATB基因的功能。鉴于此，本研究采用RACE（rapid amplification of cDNA ends）方法克隆了VfFATB基因，以进一步研究其功能。油桐种子中VfFATB的表达谱与含油量呈正相关。VfFATB定位于叶绿体中并恢复拟南芥fatb突变体的异常发育。VfFATB转化的E.大肠杆菌（Escherichia coli）细胞和拟南芥fatb突变体植物显示，VfFATB的存在导致体内18：0和18：3脂肪酸的积累。利用油桐种子组织粗提物和纯化的VfFATB蛋白进行的体外硫酯酶测定进一步表明，18：0-ACP而不是18：3-ACP是VfFATB的主要底物。以上结果表明，VfFATB是一种18：0-ACP偏好型硫酯酶，它通过水解18：0-ACP生成游离18：0脂肪酸作为下游相关酶的底物，促进18：3脂肪酸的积累，是植物正常发育所必需的。
Key message VfFATB functions in chloroplast. VfFATB expression level is positively correlated with tung oil content. VfFATB is essential for plant normal development. VfFATB is an 18:0-ACP-preferring thioesterase.Tung oil extracted from tung tree (Vernicia fordii) seeds is very industrially useful due to its drying quality given by alpha-eleostearic acid (ESA). Previous comparative transcriptome analysis revealed that a putative tung tree FATB gene (VfFATB) encoding fatty acyl-ACP (acyl carrier protein) thioesterase B (FATB) was significantly unregulated during oil synthesis stage. Fatty acyl-ACP thioesterases determine the length of the fatty acid carbon chains through releasing acyl chain from acyl-ACP. For a better understanding of the mechanism of alpha-eleostearic acid biosynthesis, it would be desirable to further characterize the function of VfFATB gene involved in fatty acid synthesis pathways in tung tree seeds. In view of this, VfFATB gene was cloned by RACE (rapid amplification of cDNA ends) method to further characterize its functions. Expression profiles of VfFATB were positively correlated with oil contents in tung tree seeds. VfFATB is localized in chloroplasts and restored the abnormal development of Arabidopsis fatb mutants. Fatty acid profiles in VfFATB-transformed E. coli (Escherichia coli) cells and Arabidopsis fatb mutant plants showed that the presence of VfFATB led to accumulation of 18:0 and 18:3 fatty acids in vivo. In vitro thioesterase assay using crude extract from seed tissue of tung tree and purified VfFATB protein further indicated that 18:0-ACP rather than 18:3-ACP was the main substrate of VfFATB. The above results strongly suggest that VfFATB, an 18:0-ACP-preferring thioesterase, is essential for plant normal development and promotes the accumulation of 18:3 fatty acid through hydrolyzing 18:0-ACP to produce free 18:0 fatty acid as the substrate of downstream related enzymes.