Functional analysis of plant nucleobase and vitamin C transporters

嘌呤和嘧啶在所有细胞的核酸和核苷酸代谢中起关键作用。此外，它们可用作许多微生物和植物中的氮源，例如用于次生化合物如细胞分裂素、某些生物碱或豆类中酰脲的生物合成。另一方面，抗坏血酸（维生素C）代表植物中保护植物细胞免受氧化胁迫的主要抗氧化剂之一。它在细胞质和线粒体中合成，在不同的细胞隔室中积累到毫摩尔浓度。有趣的是，核碱基和抗坏血酸，虽然结构上不相关，是由一个高度同源的转运蛋白家族，核碱基-抗坏血酸转运蛋白（NAT）。拟南芥基因组包含至少12个编码功能未知的NAT蛋白的基因。该项目的目的是阐明NAT蛋白家族的各种成员在发育和对环境（胁迫）条件的响应期间在细胞器和质膜中的转运特异性和生理作用，例如通过蛋白在酵母细胞和子囊菌构巢曲霉中的异源表达，使用Nothing印迹分析，cDNA微阵列，通过（亚）细胞定位研究，以及通过在分子、生物化学和生理水平上分离和表征插入突变体。

Purines and pyrimidines play a key role in nucleic acid and nucleotide metabolism of all cells. In addition, they can be used as nitrogen sources in many microorganisms and plants e.g. for the biosynthesis of secondary compounds such as cytokinins, some alkaloids or of ureides in legumes. On the other hand, ascorbate (vitamin C) represents one of the main antioxidants in plants protecting plant cells against oxidative stress. Synthesized in the cytosol and in mitochondria, it accumulates to millimolar concentrations in different cellular compartments. Interestingly, nucleobases and ascorbate, albeit structurally unrelated, are transported by a family of highly homologous transport proteins, the Nucleobase-Ascorbate Transporters (NATs). The Arabidopsis thaliana genome contains at least 12 genes encoding putative NAT proteins with yet unknown functions. The aim of this project is to elucidate the transport specificities and the physiological roles of the various members of the NAT protein family in organelles and the plasma membrane during development and response to environmental (stress) conditions, e.g. by heterologous expression of the proteins in yeast cells and the ascomycete Aspergillus nidulans, using Nothern blot assays, cDNA microarrays, by (sub)cellular localization studies, and by isolation and characterization of insertion mutants at the molecular, biochemical and physiological levels.