Department of Plant Pathology and Microbiology, University of California, Riverside, Riverside, CA 92521, USA; Center for Plant Cell Biology, University of California, Riverside, Riverside, CA 92521, USA; Institute for Integrative Genomic Biology, University of California, Riverside, Riverside, CA 92521, USA.
Environmental Toxicology Graduate Program, University of California, Riverside, Riverside, CA 92521, USA.
Cell Host Microbe. 2011 Mar 17;9(3):177-186. doi: 10.1016/j.chom.2011.02.007.
Type III secreted effectors (T3SEs), such as Pseudomonas syringae HopZ1, are essential bacterial virulence proteins injected into the host cytosol to facilitate infection. However, few direct targets of T3SEs are known. Investigating the target(s) of HopZ1 in soybean, a natural P. syringae host, we find that HopZ1 physically interacts with the isoflavone biosynthesis enzyme, 2-hydroxyisoflavanone dehydratase (GmHID1). P. syringae infection induces gmhid1 expression and production of daidzein, a major soybean isoflavone. Silencing gmhid1 increases susceptibility to P. syringae infection, supporting a role for GmHID1 in innate immunity. P. syringae expressing active but not the catalytic mutant of HopZ1 inhibits daidzein induction and promotes bacterial multiplication in soybean. HopZ1-enhanced P. syringae multiplication is at least partially dependent on GmHID1. Thus, GmHID1 is a virulence target of HopZ1 to promote P. syringae infection of soybean. This work highlights the isoflavonoid biosynthesis pathway as an antibacterial defense mechanism and a direct T3SE target.
III 型分泌效应蛋白（T3SE），如丁香假单胞菌 HopZ1，是必需的细菌毒力蛋白，可注入宿主细胞质中促进感染。然而，已知的 T3SE 直接靶标很少。在大豆（天然丁香假单胞菌宿主）中研究 HopZ1 的靶标，我们发现 HopZ1 与异黄酮生物合成酶 2-羟异黄酮脱水酶（GmHID1）发生物理相互作用。丁香假单胞菌感染诱导 gmhid1 表达和大豆中主要异黄酮大豆黄素的产生。沉默 gmhid1 会增加对丁香假单胞菌感染的敏感性，支持 GmHID1 在先天免疫中的作用。表达活性但不是催化突变体的 HopZ1 的丁香假单胞菌抑制大豆黄素诱导并促进细菌在大豆中的增殖。HopZ1 增强的丁香假单胞菌增殖至少部分依赖于 GmHID1。因此，GmHID1 是 HopZ1 促进大豆丁香假单胞菌感染的毒力靶标。这项工作突出了异黄酮生物合成途径作为一种抗菌防御机制和直接的 T3SE 靶标。
