State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China.
Mol Plant. 2023 Nov 6;16(11):1811-1831. doi: 10.1016/j.molp.2023.09.022. Epub 2023 Oct 4.
Phosphorus is an essential macronutrient for plant development and metabolism, and plants have evolved ingenious mechanisms to overcome phosphate (Pi) starvation. However, the molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions and the coordinated utilization of Pi and nitrogen remain largely unclear. Here, we show that Nodulation Signaling Pathway 1 (NSP1) and NSP2 regulate rice tiller number by promoting the biosynthesis of strigolactones (SLs), a class of phytohormones with fundamental effects on plant architecture and environmental responses. We found that NSP1 and NSP2 are induced by Oryza sativa PHOSPHATE STARVATION RESPONSE2 (OsPHR2) in response to low-Pi stress and form a complex to directly bind the promoters of SL biosynthesis genes, thus markedly increasing SL biosynthesis in rice. Interestingly, the NSP1/2-SL signaling module represses the expression of CROWN ROOTLESS 1 (CRL1), a newly identified early SL-responsive gene in roots, to restrain lateral root density under Pi deficiency. We also demonstrated that GR24 treatment under normal conditions inhibits the expression of OsNRTs and OsAMTs to suppress nitrogen absorption but enhances the expression of OsPTs to promote Pi absorption, thus facilitating the balance between nitrogen and phosphorus uptake in rice. Importantly, we found that NSP1p:NSP1 and NSP2p:NSP2 transgenic plants show improved agronomic traits and grain yield under low- and medium-phosphorus conditions. Taken together, these results revealed a novel regulatory mechanism of SL biosynthesis and signaling in response to Pi starvation, providing genetic resources for improving plant architecture and nutrient-use efficiency in low-Pi environments.
磷是植物发育和代谢所必需的大量营养素，植物已经进化出巧妙的机制来克服磷酸盐（Pi）饥饿。然而，低磷条件下对 Shoot 和 Root 结构的调控以及 Pi 和氮的协调利用的分子机制在很大程度上仍不清楚。在这里，我们表明，结瘤信号通路 1（NSP1）和 NSP2 通过促进 Strigolactones（SLs）的生物合成来调节水稻分蘖数，SLs 是一类对植物结构和环境响应具有根本影响的植物激素。我们发现，NSP1 和 NSP2 在低 Pi 胁迫下被 Oryza sativa PHOSPHATE STARVATION RESPONSE2（OsPHR2）诱导，形成复合物直接结合 SL 生物合成基因的启动子，从而显着增加水稻中 SL 的生物合成。有趣的是，NSP1/2-SL 信号模块抑制了 CROWN ROOTLESS 1（CRL1）的表达，CRL1 是根中最新鉴定的早期 SL 响应基因，以抑制缺 Pi 时侧根密度。我们还证明，在正常条件下 GR24 处理抑制 OsNRTs 和 OsAMTs 的表达以抑制氮吸收，但增强 OsPTs 的表达以促进 Pi 吸收，从而促进水稻中氮磷吸收的平衡。重要的是，我们发现 NSP1p：NSP1 和 NSP2p：NSP2 转基因植物在低磷和中磷条件下表现出更好的农艺性状和籽粒产量。总之，这些结果揭示了响应 Pi 饥饿时 SL 生物合成和信号转导的新调控机制，为在低 Pi 环境中改善植物结构和养分利用效率提供了遗传资源。
