Dirigent Protein-Mediated Lignan and Cyanogenic Glucoside Formation in Flax Seed: Integrated Omics and MALDI Mass Spectrometry Imaging
Dirigent Protein-Mediated Lignan and Cyanogenic Glucoside Formation in Flax Seed: Integrated Omics and MALDI Mass Spectrometry Imaging
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DOI：
10.1021/acs.jnatprod.5b00023
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发表时间：
2015-06-01
影响因子：
5.1
通讯作者：
Lewis, Norman G.
中科院分区：
文献类型：
--
作者：
Dalisay, Doralyn S.;Kim, Kye Won;Lewis, Norman G.
采用基因组学、转录组学、代谢组学（MALDI质谱成像，MSI）和生物信息学的综合组学方法来研究保护健康的聚合木脂素和植物防御氰苷的时空形成和沉积。对不同发育阶段的完整亚麻蒴果和种子组织进行了分析。转录组分析表明，不同的表达模式的dirigent蛋白（DP）基因家族成员编码（-）和（+）-松醇形成的DP及其相关的下游代谢过程，分别与前者在种皮发育早期阶段表达。与此相反，编码（+）-松醇形成DP的基因在发育后期表达。重组DP表达和DP测定也明确确立了其独特的立体选择性生化功能。使用MALDI MSI和离子迁移率分离分析，松醇下游衍生物，开环异落叶松树脂酚二葡萄糖苷（SDG）和SDG羟甲基戊二酸酯，仅在早期种皮发育阶段被定位和检测。然后在种皮成熟期间将SDG衍生物转化为更高分子量的酚类化合物。相比之下，植物防御生氰葡萄糖苷，单葡萄糖苷linamarin/lotaustralin，检测到整个亚麻胶囊，而双葡萄糖苷linustatin/neolinustatin只积累在胚乳和胚组织。根据转录组共表达数据，提出了一个推定的氰生物合成途径。所有代谢产物的定位均在约。20 μ m的分辨率，基于网络的工具OpenMSI不仅能够提高分辨率，而且还可以实时搜索分析组织中的任何离子。
An integrated omics approach using genomics, transcriptomics, metabolomics (MALDI mass spectrometry imaging, MSI), and bioinformatics was employed to study spatiotemporal formation and deposition of health-protecting polymeric lignans and plant defense cyanogenic glucosides. Intact flax (Linum usitatissimum) capsules and seed tissues at different development stages were analyzed. Transcriptome analyses indicated distinct expression patterns of dirigent protein (DP) gene family members encoding (-)- and (+)-pinoresinol-forming DPs and their associated downstream metabolic processes, respectively, with the former expressed at early seed coat development stages. Genes encoding (+)-pinoresinol-forming DPs were, in contrast, expressed at later development stages. Recombinant DP expression and DP assays also unequivocally established their distinct stereoselective biochemical functions. Using MALDI MSI and ion mobility separation analyses, the pinoresinol downstream derivatives, secoisolariciresinol diglucoside (SDG) and SDG hydroxymethylglutaryl ester, were localized and detectable only in early seed coat development stages. SDG derivatives were then converted into higher molecular weight phenolics during seed coat maturation. By contrast, the plant defense cyanogenic glucosides, the monoglucosides linamarin/lotaustralin, were detected throughout the flax capsule, whereas diglucosides linustatin/neolinustatin only accumulated in endosperm and embryo tissues. A putative biosynthetic pathway to the cyanogens is proposed on the basis of transcriptome coexpression data. Localization of all metabolites was at ca. 20 mu m resolution, with the web based tool OpenMSI enabling not only resolution enhancement but also an interactive system for real-time searching for any ion in the tissue under analysis.