Plant innate immunity is activated upon perception of invasion pattern molecules by plant cell-surface immune receptors. Several bacteria of the genera Pseudomonas and Burkholderia produce rhamnolipids (RLs) from L-rhamnose and (R)-3-hydroxyalkanoate precursors (HAAs). RL and HAA secretion is required to modulate bacterial surface motility, biofilm development, and thus successful colonization of hosts. Here, we show that the lipidic secretome from the opportunistic pathogen Pseudomonas aeruginosa mostly comprising RLs and HAAs stimulates Arabidopsis immunity. We demonstrate that HAAs are sensed by the bulb-type lectin receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION/S-DOMAIN-1-29 (LORE/SD1-29) that also mediates medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) perception in the plant Arabidopsis thaliana. HAA sensing induces canonical immune signaling and local resistance to plant pathogenic Pseudomonas infection. By contrast, RLs trigger an atypical immune response and resistance to Pseudomonas infection independent of LORE. Thus, the glycosyl moieties of RLs, albeit abolishing sensing by LORE, do not impair their ability to trigger plant defense. In addition, our results show that RL-triggered immune response is affected by the sphingolipid composition of the plasma membrane. In conclusion, RLs and their precursors released by bacteria can both be perceived by plants but through distinct mechanisms.

中文翻译：

---

细菌毒性因子鼠李糖脂及其（R）-3-羟基链烷酸酯前体通过两种独立的机制激活拟南芥的先天免疫力。

一旦植物细胞表面免疫受体感知到入侵模式分子，就会激活植物固有免疫力。假单胞菌属和伯克霍尔德氏菌属的几种细菌从L-鼠李糖和（R）-3-羟基链烷酸酯前体（HAA）产生鼠李糖脂（RLs）。RL和HAA分泌是调节细菌表面运动性，生物膜形成并因此成功定植宿主所必需的。在这里，我们表明机会性病原体铜绿假单胞菌的脂质分泌组主要包含RLs和HAA刺激拟南芥免疫。我们证明HAA被球型凝集素受体激酶LIPOOLIGOSACCHARIDE特异性减少的ELICITATION / S-DOMAIN-1-29（LORE / SD1-29）感应，它还介导了中链3-羟基脂肪酸（mc-3- OH-FA）在拟南芥植物中的感知。HAA感应诱导典型的免疫信号传导和对植物病原性假单胞菌感染的局部耐药性。相比之下，RL会独立于LORE触发非典型的免疫反应和对假单胞菌感染的抵抗力。因此，RLs的糖基部分尽管被LORE取消了传感，但并不损害其触发植物防御的能力。此外，我们的结果表明，RL触发的免疫反应受质膜鞘脂成分的影响。总之，细菌释放的RL及其前体都可以被植物感知，但是可以通过不同的机制来感知。尽管取消了LORE的感知，但不会损害其触发植物防御的能力。此外，我们的结果表明，RL触发的免疫反应受质膜鞘脂成分的影响。总之，细菌释放的RL及其前体都可以被植物感知，但是可以通过不同的机制来感知。尽管取消了LORE的感知，但不会损害其触发植物防御的能力。此外，我们的结果表明，RL触发的免疫反应受质膜鞘脂成分的影响。总之，细菌释放的RL及其前体都可以被植物感知，但是可以通过不同的机制来感知。