Phosphorus (P) is an indispensable macronutrient required for plant growth and development. Natural phosphate (Pi) reserves are finite, and a better understanding of Pi utilization by crops is therefore vital for worldwide food security. Ammonium has long been known to enhance Pi acquisition efficiency in agriculture; however, the molecular mechanisms coordinating Pi nutrition and ammonium remains unclear. Here, we reveal that ammonium is a novel initiator that stimulates the accumulation of a key regulatory protein, STOP1, in the nuclei of Arabidopsis root cells under Pi deficiency. We show that Pi deficiency promotes ammonium uptake mediated by AMT1 transporters and causes rapid acidification of the root surface. Rhizosphere acidification-triggered STOP1 accumulation activates the excretion of organic acids, which help to solubilize Pi from insoluble iron or calcium phosphates. Ammonium uptake by AMT1 transporters is downregulated by a CIPK23 protein kinase whose expression is directly modulated by STOP1 when ammonium reaches toxic levels. Taken together, we have identified a STOP1-centered regulatory network that links external ammonium with efficient Pi acquisition from insoluble phosphate sources. These findings provide a framework for developing possible strategies to improve crop production by enhancing the utilization of non-bioavailable nutrients in soil.

磷（P）是植物生长发育不可缺少的常量营养素。天然磷酸盐 (Pi) 储量是有限的，因此更好地了解作物对 Pi 的利用对全球粮食安全至关重要。众所周知，铵可以提高农业中的磷获取效率。然而，协调 Pi 营养和铵的分子机制仍不清楚。在这里，我们揭示了铵是一种新的引发剂，可刺激拟南芥细胞核中关键调节蛋白 STOP1 的积累缺磷的根细胞。我们表明，磷缺乏促进了由 AMT1 转运蛋白介导的铵吸收，并导致根表面快速酸化。根际酸化引发的 STOP1 积累激活有机酸的排泄，这有助于溶解不溶性磷酸铁或磷酸钙中的 Pi。AMT1 转运蛋白对铵的吸收被 CIPK23 蛋白激酶下调，当铵达到毒性水平时，其表达由 STOP1 直接调节。总之，我们已经确定了一个以 STOP1 为中心的监管网络，它将外部铵与从不溶性磷酸盐源中有效获取 Pi 联系起来。这些发现为制定可能的策略提供了一个框架，通过提高土壤中非生物可利用养分的利用来提高作物产量。