背景回顾：Phytosulfokine (PSK) is a plant pentapeptide hormone that fulfills a wide range of functions. 

提出问题：Although PSK has frequently been reported to function in the inverse regulation of growth and defense in response to (hemi)biotrophic pathogens, the mechanisms involved remain largely unknown. 

结果1-PSKR1-CPK28-GS2：Using the tomato (Solanum lycopersicum) and Pseudomonas syringae pv. tomato (Pst) DC3000 pathogen system, we present compelling evidence that the PSK receptor PSKR1 interacts with the calcium-dependent protein kinase CPK28, which in turn phosphorylates the key enzyme of nitrogen assimilation glutamine synthetase GS2 at two sites (Serine-334 and Serine-360). 

结果2-GS2不同位点磷酸化：GS2 phosphorylation at S334 specifically regulates plant defense, whereas S360 regulates growth, uncoupling the PSK-induced effects on defense responses and growth regulation. 

结论：The discovery of these sites will inform breeding strategies designed to optimize the growth-defense balance in a compatible manner.

磺肽素（PSK）是一种植物五肽激素，在植物中发挥多种功能。尽管，已经有很多报道表明PSK在植物响应（半）活体营养型病原菌时参与生长和防御的平衡调控，但涉及的具体分子机制并不清楚。本文中，作者以番茄和丁香假单胞菌番茄致病变种DC3000病原菌系统为研究对象，发现PSK的受体PSKR1能够与钙依赖蛋白激酶CPK28互作，后者能够磷酸化氮同化关键酶谷氨酰胺合成酶（GS2）的两个位点，即334号和360号位上的丝氨酸。GS2蛋白S334被磷酸化会特异性调控植物防御，而S360被磷酸化会调控植物生长，从而解偶联了PSK介导的植物防御和生长调节。本文的研究发现为将来制定平衡植物生长和防御的最优育种策略提供信息。

** 师 恺 **