Fusarium graminearum is an important plant-pathogenic fungus that causes Fusarium head blight on wheat and barley, and ear rot on maize worldwide. This fungus has been widely used as a model organism to study various biological processes of plant-pathogenic fungi because of its amenability to genetic manipulation and well-established outcross system. Gene deletion and overexpression/constitutive expression of target genes are tools widely used to investigate the molecular mechanism underlying fungal development, virulence, and secondary metabolite production. However, for fine-tuning gene expression and studying essential genes, a conditional gene expression system is necessary that enables repression or induction of gene expression by modifying external conditions. Until now, only a few conditional expression systems have been developed in plant-pathogenic fungi. This study proposes a new and versatile conditional gene expression system in F. graminearum using the promoter of a copper-responsive gene, designated F. graminearum copper-responsive 1 (FCR1). Transcript levels of FCR1 were found to be greatly affected by copper availability conditions. Moreover, the promoter (P_FCR1), 1 kb upstream of the FCR1 open reading frame, was sufficient to confer copper-dependent gene expression. Replacement of a green fluorescent protein gene and FgENA5 promoter with a P_FCR1 promoter clearly showed that P_FCR1 could be used for fine-tuning gene expression in this fungus. We also demonstrated the applicability of this conditional gene expression system to an essential gene study by replacing the promoter of FgIRE1, an essential gene of F. graminearum. This enabled the generation of FgIRE1 suppression mutants, which allowed functional characterization of the gene. This study reported the first conditional gene expression system in F. graminearum using both repression and induction. This system would be a convenient way to precisely control gene expression and will be used to determine the biological functions of various genes, including essential ones.

中文翻译：

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植物病原真菌禾谷镰刀菌通用铜响应基因表达系统的开发

禾谷镰刀菌是一种重要的植物病原真菌，在世界范围内引起小麦和大麦的镰刀菌头枯病和玉米的穗腐病。这种真菌已被广泛用作模式生物来研究植物病原真菌的各种生物学过程，因为它易于遗传操作和完善的异交系统。靶基因的基因缺失和过表达/组成型表达是广泛用于研究真菌发育、毒力和次级代谢产物产生的分子机制的工具。然而，为了微调基因表达和研究必需基因，有条件的基因表达系统是必要的，它可以通过改变外部条件来抑制或诱导基因表达。到目前为止，仅在植物病原真菌中开发了少数条件表达系统。F。 _ 禾谷镰刀菌使用铜响应基因的启动子，命名为禾谷镰刀菌铜响应 1 ( FCR1 )。发现FCR1的转录水平受铜可用性条件的影响很大。此外，在FCR1开放阅读框上游 1 kb的启动子 ( P _FCR1 )足以赋予铜依赖性基因表达。用P _FCR1启动子替换绿色荧光蛋白基因和FgENA5启动子清楚地表明P _FCR1可用于微调这种真菌中的基因表达。我们还通过替换FgIRE1的启动子（ F的必需基因）证明了这种条件基因表达系统对必需基因研究的适用性。 禾本科植物。这使得FgIRE1抑制突变体的产生成为可能，从而可以对基因进行功能表征。该研究报告了F中的第一个条件基因表达系统。 禾谷植物同时使用抑制和诱导。该系统将是一种精确控制基因表达的便捷方式，并将用于确定各种基因的生物学功能，包括基本基因。