The FRIGIDA locus (FRI, AT4G00650) has been extensively studied in Arabidopsis thaliana because of its role creating flowering time diversity. The FRI protein regulates flowering induction by binding partner proteins on its N‐terminus and C‐terminus domains and creating a supercomplex that promotes transcription of the floral repressor FLOWERING LOCUS C (FLC). Despite the knowledge accumulated on FRIGIDA (FRI), the function of the highly conserved central domain of the protein is still unknown. Functional characterization of naturally occurring DNA polymorphisms can provide useful information about the role of a protein and the localization of its operative domains. For FRI, loss‐of‐function mutations are positively selected and widespread in nature, making them a powerful tool to study the function of the different domains of the protein. Here we explore natural sequence variation in the FRI locus in more than 1000 Arabidopsis accessions. We identify 127 mutations that alter the FRI protein, including 60 that had never been described before. We defined 103 different alleles of FRI and study their association with variation in flowering time. We confirmed these associations by cloning 22 different alleles and expressing them in a common null genetic background. Our analysis pinpoints two single amino acid changes in the central domain that render the protein non‐functional. We show that these two mutations determine the stability and cellular localization of the FRI protein. In summary, our work makes use of natural variants at the FRI locus to help understanding the function of the central domain of the FRI protein.

中文翻译：

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使用拟南芥中天然存在的变异对FRIGIDA进行功能分析。

该FRIGIDA轨迹（FRI，AT4G00650）已被广泛研究拟南芥因为它的作用是创造开花时间的多样性。FRI蛋白通过在其N末端和C末端结构域上结合伴侣蛋白来调节开花诱导，并形成促进花型阻遏物FLOWERING LOCUS C（FLC）转录的超复合物。尽管积累了有关FRIGIDA（FRI）的知识，但高度保守的蛋白质中央结构域的功能仍然未知。天然存在的DNA多态性的功能表征可以提供有关蛋白质作用及其有效结构域定位的有用信息。对于FRI，功能缺失突变是经过积极选择并在自然界广泛分布的，因此使其成为研究蛋白质不同结构域功能的有力工具。在这里，我们探索FRI中的自然序列变异超过1000个拟南芥种质中的基因座。我们鉴定出127个可改变FRI蛋白的突变，其中60个以前从未描述过。我们定义了103个不同的FRI等位基因，并研究了它们与开花时间变化的关系。我们通过克隆22个不同的等位基因并在共同的无效遗传背景中表达它们来确认这些关联。我们的分析指出了中央结构域中的两个单个氨基酸变化，这些变化使蛋白质失去功能。我们显示这两个突变确定FRI蛋白的稳定性和细胞定位。总之，我们的工作利用FRI基因座的天然变异体来帮助理解FRI蛋白中央结构域的功能。