Comparative metabolomics and transcriptomics analyses provide insights into the high-yield mechanism of phenazines biosynthesis in Pseudomonas chlororaphis GP72.

Abstract

Phenazines, such as phenazine-1-carboxylic acid (PCA), phenazine-1-carboxamide (PCN), 2-hydroxyphenazine-1-carboxylic acid (2-OH-PCA), 2-hydroxyphenazine (2-OH-PHZ), are a class of secondary metabolites secreted by plant-beneficial Pseudomonas. Ps. chlororaphis GP72 utilizes glycerol to synthesize PCA, 2-OH-PCA and 2-OH-PHZ, exhibiting broad-spectrum antifungal activity. Previous studies showed that the addition of dithiothreitol (DTT) could increase the phenazines production in Ps. chlororaphis GP72AN. However, the mechanism of high yield of phenazine by adding DTT is still unclear. In this study, untargeted and targeted metabolomic analysis were adopted to determine the content of metabolites. The results showed that the addition of DTT to GP72AN affected the content of metabolites of central carbon metabolism, shikimate pathway and phenazine competitive pathway. Transcriptome analysis was conducted to investigate the changed cellular process, and the result indicated that the addition of DTT affected the expression of genes involved in phenazine biosynthetic cluster and genes involved in phenazine competitive pathway, driving more carbon flux into phenazine biosynthetic pathway. Furthermore, genes involved in antioxidative stress, phosphate transport system and mexGHI-opmD efflux pump were also affected by adding DTT. This study demonstrated that the addition of DTT altered the expression of genes related to phenazine biosynthesis, resulting in the change of metabolites involved in central carbon metabolism, shikimate pathway and phenazine competitive pathway. This work expands the understanding of high yield of phenazine by the addition of DTT and provides several targets for increasing phenazine production.