Clifford Jennifer C, Buchanan Alex, Vining Oliver, Kidarsa Teresa A, Chang Jeff H, McPhail Kerry L, Loper Joyce E
US Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, OR, USA.
Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, USA.
Environ Microbiol. 2016 Oct;18(10):3296-3308. doi: 10.1111/1462-2920.13043. Epub 2015 Oct 14.
Bacteria can be both highly communicative and highly competitive in natural habitats and antibiotics are thought to play a role in both of these processes. The soil bacterium Pseudomonas protegens Pf-5 produces a spectrum of antibiotics, two of which, pyoluteorin and 2,4-diacetylphloroglucinol (DAPG), function in intracellular and intercellular communication, both as autoinducers of their own production. Here, we demonstrate that phloroglucinol, an intermediate in DAPG biosynthesis, can serve as an intercellular signal influencing the expression of pyoluteorin biosynthesis genes, the production of pyoluteorin, and inhibition of Pythium ultimum, a phytopathogenic oomycete sensitive to pyoluteorin. Through analysis of RNAseq data sets, we show that phloroglucinol had broad effects on the transcriptome of Pf-5, significantly altering the transcription of more than two hundred genes. The effects of nanomolar versus micromolar concentrations of phloroglucinol differed both quantitatively and qualitatively, influencing the expression of distinct sets of genes or having opposite effects on transcript abundance of certain genes. Therefore, our results support the concept of hormesis, a phenomenon associated with signalling molecules that elicit distinct responses at different concentrations. Phloroglucinol is the first example of an intermediate of antibiotic biosynthesis that functions as a chemical messenger influencing gene expression in P. protegens.
在自然栖息地中，细菌既具有高度的交流能力，又具有高度的竞争性，而抗生素被认为在这两个过程中都发挥着作用。土壤细菌绿针假单胞菌Pf-5能产生一系列抗生素，其中的藤黄绿菌素和2,4-二乙酰基间苯三酚（DAPG）在细胞内和细胞间通讯中发挥作用，它们自身作为自身产生的自诱导物。在这里，我们证明间苯三酚是DAPG生物合成的中间体，可作为一种细胞间信号，影响藤黄绿菌素生物合成基因的表达、藤黄绿菌素的产生以及对终极腐霉的抑制作用，终极腐霉是一种对藤黄绿菌素敏感的植物病原卵菌。通过对RNA测序数据集的分析，我们表明间苯三酚对Pf-5的转录组有广泛影响，显著改变了两百多个基因的转录。纳摩尔浓度与微摩尔浓度的间苯三酚的作用在数量和质量上都有所不同，影响不同基因集的表达，或对某些基因的转录丰度产生相反的影响。因此，我们的结果支持毒物兴奋效应的概念，这是一种与信号分子相关的现象，信号分子在不同浓度下会引发不同的反应。间苯三酚是抗生素生物合成中间体作为化学信使影响绿针假单胞菌基因表达的首个例子。
