Allantoin accumulation through overexpression of ureide permease1 improves rice growth under limited nitrogen conditions

First author: Mark Christian Felipe R. Redillas; Affiliations: Seoul National University (首尔国立大学): Pyeongchang, Korea

Corresponding author: Ju‐Kon Kim

In legumes, nitrogen (N) can be stored as ureide allantoin (酰脲尿囊素) and transported by ureide permease (UPS) from nodules to leaves where it is catabolized to release ammonium (铵) and assimilation (同化) to amino acids. In non‐leguminous plants especially rice, information on its roles in N metabolism is scarce. Here, we show that OsUPS1 is localized in plasma membranes and are highly expressed in vascular tissues of rice. We further evaluated an activation tagging rice overexpressing OsUPS1 (OsUPS1OX) under several N regimes. Under normal field conditions, panicles from OsUPS1OX plants (14 days after flowering (DAF)) showed significant allantoin accumulation. Under hydroponic system at the vegetative stage, plants were exposed to N‐starvation and measured the ammonium in roots after resupplying with ammonium sulfate. OsUPS1OX plants displayed higher ammonium uptake in roots compared to wild type (WT). When grown under low‐N soil supplemented with different N concentrations, OsUPS1OX exhibited better growth at 50% N showing higher chlorophyll, tiller number and at least 20% increase in shoot and root biomass relative to WT. To further confirm the effects of regulating the expression of OsUPS1, we evaluated whole‐ody‐overexpressing plants driven by the GOS2 promoter (OsUPS1GOS2) as well as silencing plants (OsUPS1RNAi). We found significant accumulation of allantoin in leaves, stems and roots of OsUPS1GOS2 while in OsUPS1RNAi allantoin was significantly accumulated in roots. We propose that OsUPS1 is responsible for allantoin partitioning in rice and its overexpression can support plant growth through accumulation of allantoin in sink tissues which can be utilized when N is limiting.

在豆科植物中，氮可以被储存为酰脲尿囊素，并可以通过酰脲通透酶UPS从根瘤组织中转运到叶片中，进而在叶片中被分解代谢释放铵，最终被同化成氨基酸。在非豆科植物中，尤其是水稻中，有关UPS在氮代谢中的作用还不是很清楚。本文的研究显示OsUPS1定位于质膜上，并且在水稻的维管组织中高表达。作者进一步在不同的氮管理措施下评估了水稻OsUPS1过表达植物（OsUPS1OX）的激活标签。在正常的田间条件下，开花后14天OsUPS1OX水稻植株的穗显示出了显著的尿囊素积累。在水培法系统中，植株在营养生长阶段进行N饥饿处理，在重新提供硫酸铵的情况下，可以在植株的根中检测到铵。OsUPS1OX植株的根相比于野生型植株具有更高的铵吸收能力。当用不同程度的低水平氮浓度处理，OsUPS1OX植株相比于野生型在50%的氮条件下生长更好，具有更高的叶绿素、分蘖数和至少20%的地上和地下组织生物量。为了进一步研究OsUPS1基因表达的调控影响，作者评估了通过GOS2启动子拉整个GOS2基因的过表达植株（OsUPS1GOS2）和OsUPS1沉默植株（OsUPS1RNAi）。作者在OsUPS1GOS2植株的叶片、茎和根中尿囊素显著积累，而在OsUPS1RNAi植株中，则是根中的尿囊素显著积累。作者提出OsUPS1作用于水稻中尿囊素的分配，该基因的过表达能够通过增加库组织的铵积累，进而保证植株在N缺乏时候能够利用自身储存的氮，从而保证植株的正常生长。

doi: https://doi.org/10.1111/pbi.13054

Journal: Plant Biotechnology Journal

First Published: 19 December, 2018