Identification and characterization of highly active promoters from the fall armyworm, Spodoptera frugiperda

The cell lines derived from the fall armyworm (FAW), Spodoptera frugiperda, have been widely used for production of recombinant proteins for applications in both basic research and applications in medicine and agriculture. Promoters from the nucleopolyhedrovirus (NPV) are commonly used in these expression systems. These promoters have some limitations, which may be overcome by using promoters of genes from S. frugiperda. However, information on these promoters is not available. We identified several highly expressed genes from the transcriptomes of S. frugiperda midgut, fat body, epidermis, ovarian cell line (Sf9), and a midgut cell line (Sf17). The activity of potential promoters of 21 highly expressed genes was evaluated in Sf9 and Sf17 cells. Two of these promoters, SfHSC70-P1780 and SfPub-P2009, showed higher activity than commonly used hr5/ie1 (baculovirus enhancer element, hr5 and immediate early gene 1, ie1) promoter. Interestingly, the activity of these two promoters increased after adding hr5 enhancer element. The hr5/SfPub-P2009 promoter performance was evaluated by expressing an exogenous P450 protein in Sf9 cells using a plasmid-based expression system. The activity of this promoter was also evaluated in the FAW by expressing green fluorescence protein using the baculovirus expression system. In both cases, the hr5/SfPub-P2009 promoter performed better than the commonly used hr5/ie1 promoter. These strong endogenous promoters will benefit studies in S. frugiperda and other lepidopteran insects for multiple applications, including protein expression, genome editing, and transgenic insects.

源自秋粘虫（FAW，Spodoptera frugiperda）的细胞系，已被广泛用于生产重组蛋白，这些蛋白在基础研究以及医药和农业领域的应用中均有显著用途。在表达系统中，通常采用核多角体病毒（NPV）的启动子。然而，这些启动子存在一些局限性，通过使用来自S. frugiperda基因的启动子可能克服这些局限性。遗憾的是，关于这些启动子的信息尚不充足。我们已从S. frugiperda中肠、脂肪体、表皮、卵巢细胞系（Sf9）以及中肠细胞系（Sf17）的转录组中鉴定出数个高表达基因。在Sf9和Sf17细胞中评估了21个高表达基因潜在启动子的活性。其中两个启动子，即SfHSC70-P1780和SfPub-P2009，其活性高于常用的hr5/ie1（杆状病毒增强元件，hr5和即刻早期基因1，ie1）启动子。有趣的是，在添加hr5增强元件后，这两个启动子的活性有所提升。通过质粒介导的表达系统在Sf9细胞中表达外源P450蛋白，对hr5/SfPub-P2009启动子的性能进行了评估。此外，通过杆状病毒表达系统表达绿色荧光蛋白，在FAW中对该启动子的活性也进行了评估。在两种情况下，hr5/SfPub-P2009启动子的表现均优于常用的hr5/ie1启动子。这些强大的内源性启动子将为S. frugiperda及其他鳞翅目昆虫的研究带来诸多益处，包括蛋白质表达、基因组编辑和转基因昆虫等多个应用领域。