背景回顾：Soil availability of inorganic ortho-phosphate (PO43−, Pi) is a key determinant of plant growth and fitness. Plants regulate the capacity of their roots to take up inorganic phosphate by adapting the abundance of H+-coupled phosphate transporters of the PHOSPHATE TRANSPORTER 1 (PHT1) family at the plasma membrane (PM) through transcriptional and post-translational changes driven by the genetic network of the phosphate starvation response (PSR). Increasing evidence also shows that plants integrate immune responses to alleviate phosphate starvation stress through the association with beneficial microbes. 

提出问题：Whether and how such phosphate transport is regulated upon activation of immune responses is yet uncharacterized.

结果1-开发工具：To address this question, we first developed quantitative assays based on changes in the electrical PM potential to measure active Pitransport in roots in real time. By inserting micro-electrodes into bulging root hairs, we were able to determine key characteristics of phosphate transport in intact Arabidopsis thaliana (hereafter Arabidopsis) seedlings. 

结果2-PHT1;4作用：The fast Pi-induced depolarization observed was dependent on the activity of the major phosphate transporter PHT1;4. 

结果3-免疫响应抑制PHT1;4介导的磷转运：Notably, we observed that this PHT1;4-mediated phosphate uptake is repressed upon activation of pattern-triggered immunity. 

结果4-BIK1/PBL1介导的PHT1;4抑制：This inhibition depended on the receptor-like cytoplasmic kinases BOTRYTIS-INDUCED KINASE 1 (BIK1) and PBS1-LIKE KINASE 1 (PBL1), which both phosphorylated PHT1;4. 

结果5-PHT1;4介导的磷吸收负调控抗菌免疫：As a corollary to this negative regulation of phosphate transport by immune signaling, we found that PHT1;4-mediated phosphate uptake normally negatively regulates anti-bacterial immunity in roots. 

结论：Collectively, our results reveal a mechanism linking plant immunity and phosphate homeostasis, with BIK1/PBL1 providing a molecular integration point between these two important pathways.

 摘 要 

土壤中可利用的无机正磷酸盐是决定植物生长和适应的关键因素之一。植物通过磷饥饿PSR遗传调控网络驱动的转录和翻译后调控，调控磷酸转运蛋白PHT1家族再质膜上的富集，从而调控根系吸收土壤中无机磷的能力。越来越多的证据表明，植物整合免疫响应通过有益微生物的关联，能够减缓磷饥饿胁迫。但是，在免疫响应激活时，磷转运蛋白是否以及如何被激活还不清楚。本文中，作者为了解决该问题，首次开发了一个定量测试系统，根据质膜上电位的变化，可以实时测量根中的磷转运。通过将微型电极插入膨大的根毛中，作者能够测定完整拟南芥幼苗中磷转运的特征。快速磷诱导去极化依赖于主要的磷转运蛋白PHT1;4的活性。尤其是，作者发现PHT1;4介导的磷吸收在模式诱导免疫后受到抑制。该抑制依赖于类受体胞质激酶BIK1和PBL1，这两个激酶都能够磷酸化PHT1;4。作为免疫信号对磷转运负调控的必然结果，作者发现PHT1;4-介导的磷摄取通常也会负调控植物根系的抗菌免疫。综上，本文的研究揭示了一个连接植物免疫和磷内稳态的分子机制，其中BIK1/PBL1为这两个生物学进程提供了一个分子整合点。