Arbuscular mycorrhizal symbiosis (AMS), a complex and delicate process, is precisely regulated by a multitude of transcription factors. PHYTOCHROME-INTERACTING FACTORS (PIFs) are critical in plant growth and stress responses. However, the involvement of PIFs in AMS and the molecular mechanisms underlying their regulator functions have not been well elucidated. Here, we show that SlPIF4 negatively regulates the arbuscular mycorrhizal fungi (AMF) colonization and AMS-induced phosphate uptake in tomato. Protein–protein interaction studies suggest that SlDELLA interacts with SlPIF4, reducing its protein stability and inhibiting its transcriptional activity towards downstream target genes. This interaction promotes the accumulation of strigolactones (SLs), facilitating AMS development and phosphate uptake. As a transcription factor, SlPIF4 directly transcriptionally regulates genes involved in SLs biosynthesis, including SlCCD7, SlCDD8, and SlMAX1, as well as the AMS-specific phosphate transporter genes PT4 and PT5. Collectively, our findings uncover a molecular mechanism by which the SlDELLA-SlPIF4 module regulates AMS and phosphate uptake in tomato. We clarify a molecular basis for how SlPIF4 interacts with SLs to regulate the AMS and propose a potential strategy to improve phosphate utilization efficiency by targeting the AMS-specific phosphate transporter genes PTs.

中文翻译：

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SlDELLA 与 SlPIF4 相互作用，调节番茄丛枝菌根共生和磷酸盐摄取


丛枝菌根共生 （AMS） 是一个复杂而微妙的过程，由多种转录因子精确调节。植物色素相互作用因子 （PIF） 在植物生长和胁迫反应中至关重要。然而，PIF 参与 AMS 及其调节功能的分子机制尚未得到很好的阐明。在这里，我们表明 SlPIF4 负向调节番茄丛枝菌根真菌 （AMF） 定植和 AMS 诱导的磷酸盐摄取。蛋白质-蛋白质相互作用研究表明，SlDELLA 与 SlPIF4 相互作用，降低其蛋白质稳定性并抑制其对下游靶基因的转录活性。这种相互作用促进了独脚金内酯 （SLs） 的积累，促进了 AMS 的发展和磷酸盐的摄取。作为一种转录因子，SlPIF4 直接转录调控参与 SLs 生物合成的基因，包括 SlCCD7、SlCDD8 和 SlMAX1，以及 AMS 特异性磷酸盐转运蛋白基因 PT4 和 PT5。总的来说，我们的研究结果揭示了 SlDELLA-SlPIF4 模块调节番茄 AMS 和磷酸盐摄取的分子机制。我们阐明了 SlPIF4 如何与 SLs 相互作用以调节 AMS 的分子基础，并提出了一种通过靶向 AMS 特异性磷酸盐转运蛋白基因 PTs 来提高磷酸盐利用效率的潜在策略。