State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou, 510642, China.
Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China.
New Phytol. 2019 Oct;224(1):258-273. doi: 10.1111/nph.16028. Epub 2019 Jul 29.
The continuous growth of roots requires the balance between cell division and differentiation. Reactive oxygen species (ROS) and auxin are important regulators of root development by affecting cell division and differentiation. The mechanism controlling the coordination of cell division and differentiation is not well understood. Using a forward genetic screen, we isolated a mutant, defective primary root 2 (dpr2), defective in root apical meristem (RAM) maintenance. The DPR2 gene encodes phosphoethanolamine N-methyltransferase 1 (PEAMT1) that catalyzes phosphocholine biosynthesis in Arabidopsis. We characterized the primary root phenotypes of dpr2 using various marker lines, using histochemical and pharmacological analysis to probe early root development. Loss-of-function of DPR2/PEAMT1 resulted in RAM consumption by affecting root stem cell niche, division zone, elongation and differentiation zone (EDZ). PIN-FORMED (PIN) protein abundance, PIN2 polar distribution and general endocytosis were impaired in the root tip of dpr2. Excess hydrogen peroxide and auxin accumulate in the EDZ of dpr2, leading to RAM consumption by accelerating cell differentiation. Suppression of ROS over-accumulation or inhibition of auxin signalling partially prevent RAM differentiation in dpr2 after choline starvation. Taken together, we conclude that the EDZ of the root tip is most sensitive to choline shortage, leading to RAM consumption through an ROS-auxin regulation module.
根系的持续生长需要细胞分裂和分化之间的平衡。活性氧（ROS）和生长素通过影响细胞分裂和分化，是调控根系发育的重要调节因子。然而，控制细胞分裂和分化协调的机制还不是很清楚。我们通过正向遗传学筛选，分离到一个突变体，缺陷性主根 2（dpr2），其根顶端分生组织（RAM）维持缺陷。DPR2 基因编码磷酸乙醇胺 N-甲基转移酶 1（PEAMT1），在拟南芥中催化磷酸胆碱的生物合成。我们使用各种标记线对 dpr2 的主根表型进行了特征描述，通过组织化学和药理学分析来探测早期根发育。DPR2/PEAMT1 的功能丧失通过影响根干细胞生态位、分裂区、伸长区和分化区（EDZ），导致 RAM 消耗。在 dpr2 的根尖端，PIN 形成蛋白（PIN）蛋白丰度、PIN2 极性分布和一般内吞作用受损。dpr2 中 EDZ 中过量的过氧化氢和生长素积累，通过加速细胞分化导致 RAM 消耗。在胆碱饥饿后，ROS 过度积累的抑制或生长素信号的抑制部分阻止了 dpr2 中 RAM 的分化。综上所述，我们的结论是，根尖端的 EDZ 对胆碱缺乏最敏感，通过 ROS-生长素调节模块导致 RAM 消耗。
