Table_2_N-3-Oxo-Octanoyl Homoserine Lactone Primes Plant Resistance Against Necrotrophic Pathogen Pectobacterium carotovorum by Coordinating Jasmonic Acid and Auxin-Signaling Pathways.DOCX

Many Gram-negative bacteria use small signal molecules, such as N-acyl-homoserine lactones (AHLs), to communicate with each other and coordinate their collective behaviors. Recently, increasing evidence has demonstrated that long-chained quorum-sensing signals play roles in priming defense responses in plants. Our previous work indicated that a short-chained signal, N-3-oxo-octanoyl homoserine lactone (3OC8-HSL), enhanced Arabidopsis resistance to the hemi-biotrophic bacteria Pseudomonas syringae pv. tomato DC3000 through priming the salicylic acid (SA) pathway. Here, we found that 3OC8-HSL could also prime resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) through the jasmonic acid (JA) pathway, and is dependent on auxin responses, in both Chinese cabbage and Arabidopsis. The subsequent Pcc invasion triggered JA accumulation and increased the down-stream genes’ expressions of JA synthesis genes (LOX, AOS, and AOC) and JA response genes (PDF1.2 and VSP2). The primed state was not observed in the Arabidopsis coi1-1 and jar1-1 mutants, which indicated that the primed resistance to Pcc was dependent on the JA pathway. The 3OC8-HSL was not transmitted from roots to leaves and it induced indoleacetic acid (IAA) accumulation and the DR5 and SAUR auxin-responsive genes’ expressions in seedlings. When Arabidopsis and Chinese cabbage roots were pretreated with exogenous IAA (10 μM), the plants had activated the JA pathway and enhanced resistance to Pcc, which implied that the JA pathway was involved in AHL priming by coordinating with the auxin pathway. Our findings provide a new strategy for the prevention and control of soft rot in Chinese cabbage and provide theoretical support for the use of the quorum-sensing AHL signal molecule as a new elicitor.

众多革兰氏阴性细菌借助小型的信号分子，诸如N-酰基-高丝氨酸内酯（AHLs），相互沟通并协调其集体行为。近期，越来越多的证据表明，长链的群体感应信号在激发植物防御反应中扮演着重要角色。我们先前的研究指出，短链信号N-3-氧代辛酰高丝氨酸内酯（3OC8-HSL）通过激活水杨酸（SA）途径，增强了拟南芥对半寄生细菌黄单胞菌属番茄致病变种DC3000的抵抗力。在本研究中，我们发现3OC8-HSL亦可通过茉莉酸（JA）途径激发对软腐病菌Pectobacterium carotovorum ssp. carotovorum（Pcc）的抵抗力，此过程依赖于生长素响应，在白菜和拟南芥中均有体现。Pcc的入侵引发了JA的积累，并增加了JA合成基因（LOX、AOS和AOC）和JA反应基因（PDF1.2和VSP2）下游基因的表达。在coi1-1和jar1-1突变体中未观察到预激状态，这表明对Pcc的预激抵抗力依赖于JA途径。3OC8-HSL并未从根部传递至叶片，它在幼苗中诱导了吲哚乙酸（IAA）的积累及DR5和SAUR生长素响应基因的表达。当白菜和拟南芥的根部经外源IAA（10 μM）预处理后，植物激活了JA途径并增强了抵抗Pcc的能力，这暗示JA途径通过协调生长素途径参与了AHL的预激作用。我们的研究为白菜软腐病的预防和控制提供了一种新的策略，并为将群体感应AHL信号分子作为新型激发子应用的理论支持。