Abstract: Folylpolyglutamate synthetase (FPGS) catalyzes the addition of glutamate residues to the γ-carboxyl of tetrahydrofolate in different positions, to form folylpolyglutamates. AtDFB is the FPGS that located in plastid of Arabidopsis thaliana. In this study the Arabidopsis T-DNA insertion mutant (Atdfb-3) of AtDFB gene was used to explore the function of AtDFB gene by comparing the phenotype of wild type and atdfb-3 under various nitrogen conditions. The results showed that Atdfb-3 mutant displayed shorter primary root length and decreased folate content, compared with the wild type under the nitrogen-limited condition. The phenotype of AtDFB overexpression line under Atdfb-3 background restored to the wild-type level, and the folate content increased under the nitrogen-limited condition. In conclusion, Arabidopsis AtDFB gene plays an important role in folate biosynthesis pathway, and affects the primary root development under the nitrogen-limited condition.

Key words: folate, AtDFB gene, nitrogen-limited condition, development, Arabidopsis

摘要： 叶酰聚谷氨酸合成酶（folylpolyglutamate synthetase, FPGS）在细胞的不同位置负责将多个谷氨酸残基逐个加在单谷氨酸四氢叶酸（tetrahydrofolate, THF）的γ-羧基上，从而形成有活性的多尾形式四氢叶酸。AtDFB是定位在质体中的FPGS，利用AtDFB基因的T-DNA插入突变体Atdfb-3，通过比较野生型拟南芥及突变体在不同氮源条件下的生长状态以了解AtDFB基因的生物学功能。结果表明，低氮条件下AtDFB基因功能的缺失导致Atdfb-3突变体主根的急剧缩短，叶酸含量的明显下降；而在Atdfb-3突变体中过表达AtDFB基因后，在低氮条件下的表型恢复至野生型拟南芥水平，并且叶酸含量有所提高。综上所述，AtDFB基因在拟南芥叶酸合成代谢途径中发挥着重要作用，可能影响低氮环境下植物主根的发育。

关键词: 叶酸, AtDFB基因, 低氮胁迫, 发育, 拟南芥