Transcriptomic, Biochemical, and Morphological Study Reveals the Mechanism of Inhibition of Pseudopestalotiopsis camelliae-sinensis by Phenazine-1-Carboxylic Acid.

Qiaoxiu Yin,Xian Wu,Rui Yang,Shilong Jiang,Zhuo Chen,Yafeng Ren,Delu Wang,Tao Li,Zhiying Yang,Qin Tang,Dongxue Li,Honglin Huang

doi:10.3389/fmicb.2021.618476

Abstract

Gray blight disease is one of the most destructive diseases of tea plants and occurs widely in the tea-growing areas of the world. It is caused by several fungal phytopathogens, of which Pseudopestalotiopsis camelliae-sinensis is the main pathogen in China. The environmentally friendly antimicrobial, phenazine-1-carboxylic acid (PCA), a metabolite of the natural soil-borne bacteria Pseudomonas spp., can inhibit a range of fungal crop diseases. In this study, we determined that PCA was active against Ps. camelliae-sinensis in vitro. We studied the mode of action of PCA on hyphae using a microscopic investigation, transcriptomics, biochemical methods, and molecular docking. The results of scanning and transmission electron microscopy indicated that PCA caused developmental deformity of mycelia and organelle damage, and it significantly decreased the accumulation of exopolysaccharides on the hyphal surface. The transcriptome revealed that 1705 and 1683 differentially expressed genes of Ps. camelliae-sinensis treated with PCA were up-regulated or down-regulated, respectively, with genes associated with ribosome biogenesis, oxidative phosphorylation, and encoding various proteins of N-glycan biosynthesis being significantly up-regulated. Up-regulation of nine genes related to N-glycan biosynthesis of Ps. camelliae-sinensis in response to PCA treatment was confirmed by reverse transcription qPCR. The enzymatic activity of catalase and superoxide dismutase of hyphae was significantly decreased by PCA treatment. Our results indicated that exposure to PCA resulted in expression changes in oxidoreductase genes, accumulation of reactive oxygen species, and decreased activity of catalase, with concomitant damage to the fungal cell membrane and cell wall.

Highlights

Tea [Camellia sinensis (L.) Kuntz] is an economically important crop, the leaves of which are processed into beverages
To test the antifungal activity of phenazine-1-carboxylic acid (PCA) against the hyphal growth rate in vitro of Ps. camelliae-sinensis strain GZHS-2017-010, the mycelial growth rate was measured at PCA concentrations of 0.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 μg/ml, and significant inhibition was apparent (P < 0.05)
After the mycelium of Ps. camelliae-sinensis strain GZHS-2017-010 was treated with PCA at the EC50 concentration of 11.23 μg/ml for 12 h, the hyphae became distorted, and newly formed hyphae developed deformities and grew poorly (Figure 2B, red arrows), with the end of each freshly formed hypha becoming

Summary

Introduction

Tea [Camellia sinensis (L.) Kuntz] is an economically important crop, the leaves of which are processed into beverages. The biocontrol agents, Trichoderma harzianum, Gliocladium virens, and Pseudomonas fluorescens, have been used to prevent and effectively manage TGB (Sanjay et al, 2008). These results suggested that applying the biocontrol agents or the respective active antimicrobial factors could be a promising strategy for control of TGB (Sanjay et al, 2008; Premkumar et al, 2012; Maharachchikumbura et al, 2014)

Methods

Results

Discussion

Conclusion