低氮下拟南芥叶酰聚谷氨酸合成酶突变体atdfb根发育研究

利用叶酰聚谷氨酸合成酶功能缺失突变体atdfb解析叶酸在拟南芥根发育过程中的生物学功能。纯合T-DNA插入功能缺失突变体atdfb 在土壤培养条件下生长3周，与野生型表型无明显差异。在氮源充足的1/2MS培养基上，atdfb的主根显著短于野生型，互补植株的主根长度恢复到野生型水平，说明主根缩短的表型是由AtDFB基因功能缺失造成的。在1/2MS培养基生长11 d的突变体主根长度只有野生型的23%。在低氮条件下，突变体的生长发育几乎停滞，培养11 d的突变体主根长度只有野生型的4%；5-甲酰四氢叶酸(5-F-THF)可以恢复低氮条件下atdfb-3的表型，其主根长度、根毛长度及静止中心的细胞排列均得到恢复。进一步分析发现，低氮条件下培养少于3 d的atdfb-3补充充足的5-F-THF，3 d后能像野生型一样适应低氮环境。由此说明叶酸对拟南芥根部发育及对低氮环境的适应是必需的。

Root Development in Arabidopsis Folylpolyglutamate Synthetase Mutant adtfb under Low-nitrogen Condition

T-DNA insertion mutant of folylpolyglutamate synthetase atdfb was used to explore the role of folates during root development in Arabidopsis. Phenotype of three-week-old atdfb seedlings was similar to the wild type, however, the mutant displayed shorter primary root than the wild type on 1/2MS, and phenotype of complemented seedling was recovered indicating that the shorten root phenotype was due to the loss function of AtDFB. Length of primary root of 11-day-old atdfb-3 seedlings was 23% of the wild type on 1/2MS medium that was nitrogen (N)-sufficient conditions. The development of atdfb-3 almost stagnated under low-N conditions, and the primary root length of 11-day-old atdfb-3 seedlings was only 4% of the wild type. Under low-N conditions, exogenous 5-formyl-tetrahydrofolate (5-F-THF) restored the phenotype of atdfb-3 to the wild type. With the application of 5-F-THF, the primary root length, root hair length and the quiescent center cell organization in atdfb-3 were recovered. This study indicated the necessity of folates in Arabidopsis root development and adapting to low-N condition.