Kim In Seon, Yang Si Young, Park Seur Kee, Kim Young Cheol
Institute of Environmentally-Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 61186, South Korea.
Department of Agricultural Biology, Sunchon National University, Suncheon 57922, South Korea.
Mol Plant Pathol. 2017 Jan;18(1):134-140. doi: 10.1111/mpp.12379. Epub 2016 Apr 12.
Chromobacterium sp. strain C61 has strong biocontrol activity; however, the genetic and biochemical determinants of its plant disease suppression activity are not well understood. Here, we report the identification and characterization of two new determinants of its biocontrol activity. Transposon mutagenesis was used to identify mutants that were deficient in fungal suppression. One of these mutants had an insertion in a homologue of depD, a structural gene in the dep operon, that encodes a protein involved in non-ribosomal peptide synthesis. In the second mutant, the insertion was in a homologue of the luxI gene, which encodes a homoserine lactone synthase. The luxI and depD mutants had no antifungal activity in vitro and a dramatically reduced capacity to suppress various plant diseases in planta. Antifungal production and biocontrol were restored by complementation of the luxI mutant. Other phenotypes associated with effective biological control, including motility and lytic enzyme secretion, were also affected by the luxI mutation. Biochemical analysis of ethyl acetate extracts of culture filtrates of the mutant and wild-type strains showed that a key antifungal compound, chromobactomycin, was produced by wild-type C61 and the complemented luxI mutant, but not by the luxI or depD mutant. These data suggest that multiple biocontrol-related phenotypes are regulated by homoserine lactones in C61. Thus, quorum sensing plays an essential role in the biological control potential of diverse bacterial lineages.
嗜色杆菌属菌株C61具有很强的生防活性；然而，其植物病害抑制活性的遗传和生化决定因素尚未得到充分了解。在此，我们报告了其生防活性的两个新决定因素的鉴定和表征。转座子诱变用于鉴定在真菌抑制方面存在缺陷的突变体。其中一个突变体在depD的同源物中发生了插入，depD是dep操纵子中的一个结构基因，编码一种参与非核糖体肽合成的蛋白质。在第二个突变体中，插入发生在luxI基因的同源物中，该基因编码一种高丝氨酸内酯合酶。luxI和depD突变体在体外没有抗真菌活性，并且在植物体内抑制各种植物病害的能力显著降低。通过luxI突变体的互补恢复了抗真菌物质的产生和生防作用。与有效生物防治相关的其他表型，包括运动性和裂解酶分泌，也受到luxI突变的影响。对突变体和野生型菌株培养滤液的乙酸乙酯提取物进行生化分析表明，关键的抗真菌化合物嗜色杆菌素是由野生型C61和互补的luxI突变体产生的，但不是由luxI或depD突变体产生的。这些数据表明，C61中的高丝氨酸内酯调节多种与生防相关的表型。因此，群体感应在不同细菌谱系的生物防治潜力中起着至关重要的作用。
