Inorganic orthophosphate (Pi) is an essential nutrient for plant growth, and its availability strongly impacts crop yield. PHOSPHATE1 (PHO1) transfers Pi from root to shoot via Pi export into root xylem vessels. In this work, we demonstrate that an upstream open reading frame (uORF) present in the 5' untranslated region of the Arabidopsis (Arabidopsis thaliana) PHO1 inhibits its translation and influences Pi homeostasis. The presence of the uORF strongly inhibited the translation of a PHO1 5'UTR-luciferase construct in protoplasts. A point mutation removing the PHO1 uORF (uORF) in transgenic Arabidopsis resulted in increased association of its mRNA with polysomes and led to higher PHO1 protein levels, independent of Pi availability. Interestingly, deletion of the uORF led to higher shoot Pi content and was associated with improved shoot growth under low external Pi supply and no deleterious effects under Pi-sufficient conditions. We further show that natural accessions lacking the PHO1 uORF exhibit higher PHO1 protein levels and shoot Pi content. Increased shoot Pi content was linked to the absence of the PHO1 uORF in a population of F2 segregants. We identified the PHO1 uORF in genomes of crops such as rice (Oryza sativa), maize (Zea mays), barley (Hordeum vulgare), and wheat (Triticum aesativum), and we verified the inhibitory effect of the rice PHO1 uORF on translation in protoplasts. Our work suggests that regulation of PHO1 expression via its uORF might be a genetic resource useful—both in natural populations and in the context of genome editing—toward improving plant growth under Pi-deficient conditions.

无机正磷酸盐 (Pi) 是植物生长必需的营养素，其可用性强烈影响作物产量。磷酸盐 1 (PHO1) 通过 Pi 输出到根木质部导管，将 Pi 从根转移到芽。在这项工作中，我们证明了拟南芥 ( Arabidopsis thaliana ) PHO1 5'非翻译区中存在的上游开放阅读框 (uORF)抑制其翻译并影响 Pi 稳态。uORF 的存在强烈抑制原生质体中PHO1 5'UTR-荧光素酶构建体的翻译。转基因拟南芥中去除PHO1 uORF (uORF)的点突变导致其 mRNA 与多核糖体的关联增加，并导致更高的 PHO1 蛋白水平，与 Pi 的可用性无关。有趣的是，uORF 的缺失导致了较高的芽 Pi 含量，并且与外部 Pi 供应量较低时芽生长的改善有关，并且在 Pi 充足的条件下没有有害影响。我们进一步表明，缺乏PHO1 uORF的天然种质表现出更高的 PHO1 蛋白水平和芽 Pi 含量。芽Pi含量的增加与F2分离子群体中PHO1 uORF的缺失有关。我们在水稻 ( Oryza sativa )、玉米 ( Zea mays )、大麦 ( Hordeum vulgare ) 和小麦 ( Triticum aesativum )等作物的基因组中鉴定出了PHO1 uORF，并验证了水稻PHO1 uORF 对翻译的抑制作用。原生质体。我们的工作表明，通过 uORF 调节 PHO1 的表达可能是一种有用的遗传资源，无论是在自然群体中还是在基因组编辑的背景下，对于改善 Pi 缺乏条件下的植物生长都是有用的。