Department of Plant Pathology, China Agricultural University, Beijing, China.
Beijing Centre for Physical and Chemical Analysis, Beijing, 100089, China.
Microbiol Res. 2018 Jan;206:159-167. doi: 10.1016/j.micres.2017.10.006. Epub 2017 Oct 16.
Pseudomonas fluorescens 2P24 produces 2,4-diacetylphloroglucinol (2,4-DAPG) as the major antibiotic compound that protects plants from soil-borne diseases. Expression of the 2,4-DAPG biosynthesis enzymes, which are encoded by the phlACBD locus, is under the control of a delicate regulatory network. In this study, we identified a novel role for the outer membrane protein gene oprF, in negatively regulating the 2,4-DAPG production by using random mini-Tn5 mutagentsis. A sigma factor gene sigX was located immediately upstream of the oprF gene and shown to be a positive regulator for oprF transcription and 2,4-DAPG production. Genetic analysis of an oprF and sigX double-mutant indicated that the 2,4-DAPG regulation by oprF was dependent on SigX. The sigX gene did not affect PhlA and PhlD expression, but positively regulated the level of malonyl-CoA, the substrate of 2,4-DAPG synthesis, by influencing the expression of acetyl-CoA carboxylases. Further investigations revealed that sigX transcription was induced under conditions of salt starvation or glycine addition. All these findings indicate that SigX is a novel regulator of substrate supplements for 2,4-DAPG production.
荧光假单胞菌 2P24 产生 2,4-二乙酰基间苯三酚（2,4-DAPG）作为主要的抗生素化合物，可保护植物免受土壤传播的疾病侵害。2,4-DAPG 生物合成酶的表达由 phlACBD 基因座编码，受精细调控网络的控制。在这项研究中，我们使用随机 mini-Tn5 突变体鉴定了外膜蛋白基因 oprF 的一个新功能，它可负调控 2,4-DAPG 的产生。sigma 因子基因 sigX 位于 oprF 基因的上游，被证明是 oprF 转录和 2,4-DAPG 产生的正调控因子。对 oprF 和 sigX 双突变体的遗传分析表明，oprF 对 2,4-DAPG 的调控依赖于 SigX。sigX 基因不影响 PhlA 和 PhlD 的表达，但通过影响乙酰辅酶 A 羧化酶的表达，正向调控 2,4-DAPG 合成的底物丙二酰辅酶 A 的水平。进一步的研究表明，sigX 转录在盐饥饿或甘氨酸添加条件下被诱导。所有这些发现表明 SigX 是 2,4-DAPG 生产底物补充的新型调节剂。
