The cyanobacterium Nostoc punctiforme can form lipid droplets (LDs), internal inclusions containing triacylglycerols, carotenoids and alkanes. LDs are enriched for a 17 carbon-long alkane in N. punctiforme , and it has been shown that the overexpression of the aar and ado genes results in increased LD and alkane production. To identify transcriptional adaptations associated with increased alkane production, we performed comparative transcriptomic analysis of an alkane overproduction strain. RNA-seq data identified a large number of highly upregulated genes in the overproduction strain, including genes potentially involved in rRNA processing, mycosporine-glycine production and synthesis of non-ribosomal peptides, including nostopeptolide A. Other genes encoding helical carotenoid proteins, stress-induced proteins and those for microviridin synthesis were also upregulated. Construction of N. punctiforme strains with several upregulated genes or operons on multi-copy plasmids resulted in reduced alkane accumulation, indicating possible negative regulators of alkane production. A strain containing four genes for microviridin biosynthesis completely lost the ability to synthesize LDs. This strain exhibited wild-type growth and lag phase recovery under standard conditions, and slightly faster growth under high light. The transcriptional changes associated with increased alkane production identified in this work will provide the basis for future experiments designed to use cyanobacteria as a production platform for biofuel or high-value hydrophobic products.

中文翻译：

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蓝藻烷烃过量生产的转录组学分析揭示了与压力相关的基因和脂滴形成的抑制剂。

蓝细菌Nostoc punctiforme可以形成脂滴 (LDs)，内部包裹体含有三酰甘油、类胡萝卜素和烷烃。N. punctiforme 中LDs 富含 17 个碳长的烷烃，并且已经表明aar和ado的过度表达 基因导致 LD 和烷烃产量增加。为了确定与烷烃产量增加相关的转录适应，我们对烷烃过量生产菌株进行了比较转录组学分析。RNA-seq 数据在过度生产菌株中鉴定了大量高度上调的基因，包括可能参与 rRNA 加工、霉菌孢素-甘氨酸生产和非核糖体肽合成的基因，包括 nostopeptolide A。其他编码螺旋类胡萝卜素蛋白的基因、应激-诱导蛋白和用于微病毒素合成的蛋白也被上调。点状猪笼草的构建 在多拷贝质粒上具有几个上调基因或操纵子的菌株导致烷烃积累减少，表明烷烃产生的可能负调节剂。含有四个微病毒素生物合成基因的菌株完全失去了合成 LDs 的能力。该菌株在标准条件下表现出野生型生长和滞后期恢复，在强光下生长稍快。在这项工作中确定的与增加烷烃产量相关的转录变化将为未来旨在使用蓝藻作为生物燃料或高价值疏水产品生产平台的实验提供基础。