多个调控元件调控萜类合成途径基因表达提高β-胡萝卜素的生产

Modulation of isoprenoid gene expression with multiple regulatory parts for improved β-carotene production

摘要:

强启动子对于获得目标产物最大代谢流量来说并不一定是最优的；相比之下，使用多个具有不同强度的调控元件对基因表达进行调控更有可能获得最优的表达强度。为了对比使用多个调控元件和使用强启动子调控萜类合成途径基因表达对β-胡萝卜素生产的影响，并通过对关键基因的组合调控提高β-胡萝卜素的生产。文中使用6个强度差异很大的人工调控元件，对萜类合成途径的8个基因进行调控。对于不同的基因，其最适的调控元件强度各不相同。对8个基因的调控使β-胡萝卜素产量提高1.2~3.5倍。和以前报道不一样的是，文中发现用适当强度的调控元件对dxr、ispG和ispH基因进行调控后，也能提高β-胡萝卜素的生产。对dxs和idi基因的组合调控将β-胡萝卜素产量提高了8倍，最终β-胡萝卜素产量达17.59 mg/g干重细胞。结果表明使用多个不同强度的调控元件对基因表达进行调控比仅使用强启动子调控更为有效，为提高目标产品合成能力提供了一种新的基因表达调控方案。

关键词:调控元件，基因表达调控，β-胡萝卜素，类异戊二烯，大肠杆菌

Abstract:

Strong promoters might not be optimal to obtain maximum metabolic flux towards desired products, whereas modulating gene expression with multiple regulatory parts is an option to obtain optimal expression strength. Therefore, we assessed the difference of impact on β-carotene production between modulating isoprenoid gene expression with multiple regulatory parts and strong promoter, to improve β-carotene production through combined modulation of essential isoprenoid genes. Eight isoprenoid genes were modulated with six artificial regulatory parts having a wide range of strengths to assess their effects on β-carotene production. Optimal strength for each isoprenoid gene expression was identified, leading to 1.2 to 3.5-fold increase in β-carotene production. In contrast to previous reports, our work suggests that modulating dxr, ispG and ispH genes with appropriate strengths increase β-carotene production. β-carotene yield reached 17.59 mg/g after combined modulation of dxs and idi genes, 8-fold higher than that of the parent strain. Modulating gene expression with multiple regulatory parts was better than strong promoter, providing a new gene modulation strategy for targeted biosynthesis.

Key words:regulatory parts, modulation of gene expression, β-carotene, isoprenoid, Escherichia coli