Tissue-specific differences in metabolites and transcripts contribute to the heterogeneity of ricinoleic acid accumulation in Ricinus communis L. (castor) seeds
Tissue-specific differences in metabolites and transcripts contribute to the heterogeneity of ricinoleic acid accumulation in Ricinus communis L. (castor) seeds
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DOI：
10.1007/s11306-018-1464-3
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发表时间：
2019-01-01
期刊：
影响因子：
3.6
通讯作者：
Chapman, Kent D.
中科院分区：
文献类型：
--
作者：
Sturtevant, Drew;Romsdahl, Trevor B.;Chapman, Kent D.
蓖麻（Ricinus communis L.）种子的价值在于其生产的油可以包含高达90%的羟基脂肪酸（蓖麻油酸）。蓖麻油含有含有三酰甘油（TAGs）的单、二和三蓖麻油酸。虽然蓖麻油酸的酶合成已经被很好地描述，但这些TAG分子种类的差异区室化仍然不明确。目的研究蓖麻种子胚乳和胚组织中羟基脂肪酸的分布。方法采用基质辅助激光解吸/电离质谱法对蓖麻种子组织切片中甘油三酯的分布进行分析。此外，解剖提取胚乳和胚（子叶和胚轴）组织，进行定量脂质组学分析和基于illumina的RNA深度测序。结果本研究揭示了蓖麻种子胚和胚乳组织中单羟基、二羟基和三羟基三酰基甘油的异质分布。基于转录丰度的途径分析表明，蓖麻油酸从磷脂酰胆碱（PC）转运到羟基TAG的产生可能存在不同的胚胎和胚乳特异性机制。胚胎偏向机制似乎有利于通过磷脂酰胆碱：二酰基甘油酰基转移酶从卵磷脂池中去除蓖麻油酸，而胚乳途径似乎通过磷脂酶A（PLA(2)）和/或磷脂酰胆碱：二酰基甘油胆碱磷酸转移酶从卵磷脂池中去除蓖麻油酸。总的来说，脂质组学和转录组学分析的结合揭示了蓖麻籽中羟基脂肪酸代谢的先前未定义的空间方面。这些研究强调了组织特异性研究的必要性，以更好地了解油籽中甘油三酯积累的调节。
IntroductionCastor (Ricinus communis L.) seeds are valued for their production of oils which can comprise up to 90% hydroxy-fatty acids (ricinoleic acid). Castor oil contains mono-, di- and tri- ricinoleic acid containing triacylglycerols (TAGs). Although the enzymatic synthesis of ricinoleic acid is well described, the differential compartmentalization of these TAG molecular species has remained undefined.ObjectivesTo examine the distribution of hydroxy fatty acid accumulation within the endosperm and embryo tissues of castor seeds.MethodsMatrix assisted laser desorption/ionization mass spectrometry imaging was used to map the distribution of triacylglycerols in tissue sections of castor seeds. In addition, the endosperm and embryo (cotyledons and embryonic axis) tissues were dissected and extracted for quantitative lipidomics analysis and Illumina-based RNA deep sequencing.ResultsThis study revealed an unexpected heterogeneous tissue distribution of mono-, di- and tri- hydroxy-triacylglycerols in the embryo and endosperm tissues of castor seeds. Pathway analysis based on transcript abundance suggested that distinct embryo- and endosperm-specific mechanisms may exist for the shuttling of ricinoleic acid away from phosphatidylcholine (PC) and into hydroxy TAG production. The embryo-biased mechanism appears to favor removal of ricinoleic acid from PC through phophatidylcholine: diacylglycerol acyltransferase while the endosperm pathway appears to remove ricinoleic acid from the PC pool by preferences of phospholipase A (PLA(2)) and/or phosphatidylcholine: diacylglycerol cholinephosphotransferase.ConclusionsCollectively, a combination of lipidomics and transcriptomics analyses revealed previously undefined spatial aspects of hydroxy fatty acid metabolism in castor seeds. These studies underscore a need for tissue-specific studies as a means to better understand the regulation of triacylglycerol accumulation in oilseeds.