College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, No.1 Weigang, Nanjing City, Jiangsu Province, 210095, People's Republic of China.
Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.
Appl Microbiol Biotechnol. 2019 Feb;103(4):1811-1822. doi: 10.1007/s00253-018-09596-9. Epub 2019 Jan 7.
Spermidine is a common polyamine compound produced in bacteria, but its roles remain poorly understood. The bacterial SpeD encodes an S-adenosylmethionine decarboxylase that participates in spermidine synthesis. Lysobacter enzymogenes is an efficient environmental predator of crop fungal pathogens by secreting an antifungal antibiotic HSAF (heat-stable antifungal factor), while Clp is a master transcription factor essential for the antifungal activity of L. enzymogenes. In this work, we observed that speD was a close genomic neighbor of the clp gene. This genomic arrangement also seems to occur in many other bacteria, but the underlying reason remains unclear. By using L. enzymogenes OH11 as a working model, we showed that SpeD was involved in spermidine production that was essential for the L. enzymogenes antifungal activity. Spermidine altered the bacterial growth capability and HSAF production, both of which critically contributed to the L. enzymogenes antifungal activity. We further found that spermidine in L. enzymogenes was able to play a crucial, yet indirect role in maintaining the Clp level in vivo, at least partially accounting for its role in the antifungal activity. Thus, our findings suggested that spermidine probably plays an uncharacterized role in maintaining the levels of the master transcription regulator Clp to optimize its role in antifungal activity in an agriculturally beneficial bacterium.
亚精胺是一种常见的多胺化合物，在细菌中产生，但它的作用仍知之甚少。细菌 SpeD 编码一种 S-腺苷甲硫氨酸脱羧酶，参与亚精胺的合成。生防菌 Lysobacter enzymogenes 通过分泌一种抗真菌抗生素 HSAF（热稳定抗真菌因子）来有效捕食作物真菌病原体，而 Clp 是生防菌 Lysobacter enzymogenes 抗真菌活性所必需的主转录因子。在这项工作中，我们观察到 speD 是 clp 基因的近基因组邻居。这种基因组排列似乎也存在于许多其他细菌中，但背后的原因尚不清楚。通过使用 L. enzymogenes OH11 作为工作模型，我们表明 SpeD 参与了亚精胺的产生，这对 L. enzymogenes 的抗真菌活性至关重要。亚精胺改变了细菌的生长能力和 HSAF 的产生，这两者都对 L. enzymogenes 的抗真菌活性有重要贡献。我们进一步发现，L. enzymogenes 中的亚精胺能够在体内发挥关键但间接的作用，维持 Clp 水平，至少部分解释了它在抗真菌活性中的作用。因此，我们的研究结果表明，亚精胺可能在维持主转录调节因子 Clp 的水平方面发挥着未被描述的作用，以优化其在农业有益细菌中的抗真菌活性。
