Data_Sheet_1_Semi-Quantitative Targeted Gas Chromatography-Mass Spectrometry Profiling Supports a Late Side-Chain Reductase Cycloartenol-to-Cholesterol Biosynthesis Pathway in Brown Algae.PDF

Sterols are biologically important molecules that serve as membrane fluidity regulators and precursors of signaling molecules, either endogenous or involved in biotic interactions. There is currently no model of their biosynthesis pathways in brown algae. Here, we benefit from the availability of genome data and gas chromatography-mass spectrometry (GC-MS) sterol profiling using a database of internal standards to build such a model. We expand the set of identified sterols in 11 species of red, brown, and green macroalgae and integrate these new data with genomic data. Our analyses suggest that some metabolic reactions may be conserved despite the loss of canonical eukaryotic enzymes, like the sterol side-chain reductase (SSR). Our findings are consistent with the principle of metabolic pathway drift through enzymatic replacement and show that cholesterol synthesis from cycloartenol may be a widespread but variable pathway among chlorophyllian eukaryotes. Among the factors contributing to this variability, one could be the recruitment of cholesterol biosynthetic intermediates to make signaling molecules, such as the mozukulins. These compounds were found in some brown algae belonging to Ectocarpales, and we here provide a first mozukulin biosynthetic model. Our results demonstrate that integrative approaches can already be used to infer experimentally testable models, which will be useful to further investigate the biological roles of those newly identified algal pathways.

甾醇是一类在生物学上至关重要的分子，它们不仅调节细胞膜的流动性，还是内源性信号分子及参与生物间相互作用的物质的前体。目前，关于褐藻中甾醇的生物合成途径尚无模型。在此，得益于基因组数据的可用性和利用内部标准数据库进行的气相色谱-质谱（GC-MS）甾醇分析，我们得以构建此类模型。我们扩展了在11种红藻、褐藻和绿藻中已识别的甾醇集合，并将这些新数据与基因组数据相结合。我们的分析表明，尽管经典真核生物酶（如甾醇侧链还原酶[SSR]）可能丢失，某些代谢反应仍可能得到保留。我们的发现与代谢途径漂移原理相一致，并表明从环阿屯醇合成胆固醇可能是一种在叶绿素真核生物中普遍存在但存在差异的途径。造成这种差异的因素之一可能是将胆固醇生物合成中间体招募为信号分子，例如莫祖库林。这些化合物在一些属于Ectocarpales的褐藻中被发现，我们在此提供了第一个莫祖库林生物合成模型。我们的结果表明，整合方法已经被用来推断实验可验证的模型，这将对进一步研究这些新识别的海藻途径的生物学作用大有裨益。