Key Laboratory of Horticultural Plant Biology, MOE, and Key Laboratory of Horticultural Crop Biology and Genetic Improvement (Central Region), MOA, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
College of Horticulture, Henan Agricultural University, Zhengzhou, Henan, 450002, China.
Plant J. 2023 Mar;113(5):969-985. doi: 10.1111/tpj.16093. Epub 2023 Jan 31.
Folate (vitamin B9) is important for plant root development, but the mechanism is largely unknown. Here we characterized a root defective mutant, folb2, in Arabidopsis, which has severe developmental defects in the primary root. The root apical meristem of the folb2 mutant is impaired, and adventitious roots are frequently found at the root-hypocotyl junction. Positional cloning revealed that a 61-bp deletion is present in the predicted junction region of the promoter and the 5' untranslated region of AtFolB2, a gene encoding a dihydroneopterin aldolase that functions in folate biosynthesis. This mutation leads to a significant reduction in the transcript level of AtFolB2. Liquid chromatography-mass spectrometry analysis showed that the contents of the selected folate compounds were decreased in folb2. Arabidopsis AtFolB2 knockdown lines phenocopy the folb2 mutant. On the other hand, the application of exogenous 5-formyltetrahydrofolic acid could rescue the root phenotype of folb2, indicating that the root phenotype is indeed related to the folate level. Further analysis revealed that folate could promote rootward auxin transport through auxin transporters and that folate may affect particular auxin/indole-3-acetic acid proteins and auxin response factors. Our findings provide new insights into the important role of folic acid in shaping root structure.
叶酸（维生素 B9）对植物根的发育很重要，但机制在很大程度上尚不清楚。在这里，我们对拟南芥中的一个根缺陷突变体 folb2 进行了描述，该突变体的主根发育严重缺陷。folb2 突变体的根尖分生组织受损，不定根经常在根-下胚轴交界处发现。定位克隆表明，在 AtFolB2 基因的启动子和 5'非翻译区的预测连接区存在 61 个碱基对的缺失，AtFolB2 基因编码一种二氢蝶啶醛缩酶，该酶在叶酸生物合成中起作用。这种突变导致 AtFolB2 的转录水平显著降低。液相色谱-质谱分析显示，folb2 中的选定叶酸化合物含量降低。AtFolB2 的拟南芥敲低系表现出与 folb2 突变体相似的表型。另一方面，外源性 5-甲酰四氢叶酸的应用可以挽救 folb2 的根表型，表明根表型确实与叶酸水平有关。进一步的分析表明，叶酸可以通过生长素转运蛋白促进根向的生长素运输，并且叶酸可能影响特定的生长素/吲哚-3-乙酸蛋白和生长素反应因子。我们的研究结果为叶酸在塑造根结构中的重要作用提供了新的见解。
