• How plants balance growth and stress adaptation is a long-standing topic in plant biology. Abscisic acid (ABA) induces the expression of the stress-responsive Asparagine Rich Protein (NRP), which promotes the vacuolar degradation of PP6 phosphatase FyPP3, releasing ABI5 transcription factor to initiate transcription. Whether NRP is required for growth remains unknown.
• We generated an nrp1 nrp2 double mutant, which had a dwarf phenotype that can be rescued by inhibiting auxin transport. Insufficient auxin in the transition zone and over-accumulation of auxin at the root tip was responsible for the short elongation zone and short-root phenotype of nrp1 nrp2.
• The auxin efflux carrier PIN2 over-accumulated in nrp1 nrp2 and became de-polarized at the plasma membrane, leading to slower root basipetal auxin transport. Knock-out of PIN2 suppressed the dwarf phenotype of nrp1 nrp2. Furthermore, ABA can induce NRP-dependent vacuolar degradation of PIN2 to inhibit primary root elongation. FyPP3 also is required for NRP-mediated PIN2 turnover.
• In summary, in growth condition, NRP promotes PIN2 vacuolar degradation to help maintain PIN2 protein concentration and polarity, facilitating the establishment of the elongation zone and primary root elongation. When stressed, ABA employs this pathway to inhibit root elongation for stress adaptation.

中文翻译：

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脱落酸利用 NRP 依赖的 PIN2 液泡降解来抑制生长素介导的拟南芥初生根伸长

• 植物如何平衡生长和压力适应是植物生物学中长期存在的话题。脱落酸 (ABA) 诱导应激反应性富含天冬酰胺蛋白 (NRP) 的表达，从而促进 PP6 磷酸酶 FyPP3 的液泡降解，释放 ABI5 转录因子以启动转录。生长是否需要 NRP 仍然未知。
• 我们生成了一个nrp1 nrp2双突变体，它具有矮小的表型，可以通过抑制生长素转运来挽救。过渡区生长素不足和根尖生长素过度积累是造成nrp1 nrp2短伸长区和短根表型的原因。
• 生长素流出载体 PIN2 在nrp1 nrp2 中过度积累，并在质膜处去极化，导致根基生长素运输变慢。敲除PIN2抑制了nrp1 nrp2的矮化表型。此外，ABA可以诱导PIN2的NRP依赖性液泡降解以抑制初生根伸长。NRP 介导的 PIN2 转换也需要 FyPP3。
• 综上所述，在生长条件下，NRP促进PIN2液泡降解，有助于维持PIN2蛋白浓度和极性，促进伸长区的建立和初生根伸长。当受到压力时，ABA 会利用这种途径来抑制根系伸长以适应压力。