背景回顾：Plants usually suffer from phosphorus starvation because of the low-phosphate (Pi) status of most soils. To cope with this, plants have evolved an adaptive phosphate starvation response (PSR) which involves both developmental and metabolic changes regulated mainly by PHOSPHATE STARVATION RESPONSE1 (PHR1) and its homologs.  

提出问题：Here, we elucidated how perennial woody plants, such as poplars (Populus spp.), respond to low-Pi stress. 

结果1-PtoWRKY40低磷响应：We first performed RNA-seq analysis of low-Pi treated poplars and identified PtoWRKY40 is rapidly down-regulated and protein degraded after stress. 

结果2-PtoWRKY40功能：Overexpressing and knocking-down PtoWRKY40 down-regulated and up-regulated the expression of Pi starvation signaling genes, respectively, such as PHOSPHATE TRANSPORTER1 (PHT1)-type genes and PURPLE ACID PHOSPHATASE (PAP) genes. 

结果3-PtoWRKY4下游：PtoWRKY40 bound to the W box in the promoter of several PtoPHT1s and repressed their expression. 

结果4-PtoWRKY4互作蛋白：Moreover, PtoWRKY40 interacted with PtoPHR1-LIKE3 (PtoPHL3), a PHR1 homolog in poplar, to inhibit the latter binding to the P1BS element and thus reduced PtoPHT1s’ transcription under Pi sufficient conditions. 

结果5-PtoWRKY4作用机制：However, Pi deficiency decreased PtoWRKY40 abundance and therefore released its inhibition on PHT1s. 

结论：In conclusion, we have uncovered a PSR mechanism mediated by PtoWRKY40 and PtoPHL3 which regulates Pi content in poplars, deepening our understanding of how poplars adapt to diverse Pi conditions and regulate appropriate responses to maintain Pi homeostasis.

 摘 要 

由于大多数的土壤都处于低磷状态，因此植物通常会遭受磷饥饿。为了应对这种情况，植物演化出一种适应性的磷饥饿响应（PSR），该过程主要涉及由磷饥饿响应蛋白PHR1及其同系物调节的发育和代谢变化。本文中，作者揭示了杨树等多年生木本植物是如何应对低磷胁迫的。作者首先对低磷处理的杨树进行了RNA-seq，发现PtoWRKY40基因的表达在低磷胁迫后被迅速下调且蛋白降解。过表达和敲低PtoWRKY40基因分别能够下调和上调磷饥饿信号转导基因的表达，如磷酸转运蛋白编码基因PHT1s和紫色酸性磷酸酶编码基因PAPs。PtoWRKY40能够结合到一些PtoPHT1s基因启动子中W-box上，并抑制后者的表达。此外，PtoWRKY40与杨树PHR1同源蛋白PtoPHL3相互作用，抑制后者与P1BS元件的结合，从而在磷充分条件下减少PtoPHT1s的转录。然而，磷缺乏降低了PtoWRKY40蛋白的丰度，从而释放了其对PHT1s的抑制。综上，本文的研究揭示了一个由PtoWRKY40和PtoPHL3介导的PSR机制，调控杨树中的磷含量，加深了我们对杨树如何适应不同磷条件及调节适当响应以维持磷稳态的理解。