Laboratorio Integral de Investigación en Alimentos, Departamento de Química y Bioquímica, Tecnológico Nacional de México, Instituto Tecnológico de Tepic, 63175 Nayarit, Mexico.
Institute for Multidisciplinary Research in Applied Biology (IMAB), Universidad Pública de Navarra (UPNA), Edificio de Agrobiotecnología, Avda. de Pamplona 123, 31192 Mutilva Baja, Spain.
Toxins (Basel). 2021 Sep 7;13(9):628. doi: 10.3390/toxins13090628.
The bean () pathogen pv. phaseolicola NPS3121 synthesizes phaseolotoxin in a thermoregulated way, with optimum production at 18 °C. Gene was previously shown to be thermoregulated and required for phaseolotoxin biosynthesis. Here, we established that is part of a cluster of 16 genes, the Pbo cluster, included in a genomic island with a limited distribution in and unrelated to the possession of the phaseolotoxin biosynthesis cluster. We identified typical non-ribosomal peptide synthetase, and polyketide synthetase domains in several of the deduced products. RT-PCR and the analysis of polar mutants showed that the Pbo cluster is organized in four transcriptional units, including one monocistronic and three polycistronic. Operons and are both essential for phaseolotoxin biosynthesis, while and only influence the amount of toxin produced. The three polycistronic units were transcribed at high levels at 18 °C but not at 28 °C, whereas gene was constitutively expressed. Together, our data suggest that the Pbo cluster synthesizes secondary metabolite(s), which could participate in the regulation of phaseolotoxin biosynthesis.
菜豆晕病假单胞菌 NPS3121 以温度调节的方式合成菜豆毒素，最佳生产温度为 18°C。先前的研究表明基因受温度调节，是菜豆毒素生物合成所必需的。在这里，我们确定是包含在一个基因组岛上的 16 个基因簇的一部分，该基因簇与菜豆毒素生物合成簇的存在无关，且在中分布有限。我们在几个推导的产物中鉴定出了典型的非核糖体肽合成酶和聚酮合酶结构域。RT-PCR 和极性突变体分析表明，Pbo 基因簇由四个转录单元组成，包括一个单顺反子和三个多顺反子。和操纵子都对菜豆毒素生物合成是必需的，而和操纵子仅影响毒素的产生量。三个多顺反子单元在 18°C 时以高水平转录，但在 28°C 时不转录，而基因则组成型表达。总之，我们的数据表明 Pbo 基因簇合成了次生代谢物，这些代谢物可能参与菜豆毒素生物合成的调控。
