Comparative Transcriptome Profiling of Gaeumannomyces graminis var. tritici in Wheat Roots in the Absence and Presence of Biocontrol Bacillus velezensis CC09

Abstract

This study aimed to explore potential biocontrol mechanisms involved in the interference of antagonistic bacteria with fungal pathogenicity in planta . To do this, we conducted a comparative transcriptomic analysis of the “take-all” pathogenic fungus Gaeumannomyces graminis var. tritici ( Ggt ) by examining Ggt -infected wheat roots in the presence or absence of the biocontrol agent Bacillus velezensis CC09 ( Bv ) compared with Ggt grown on potato dextrose agar (PDA) plates. A total of 4,134 differentially expressed genes (DEGs) were identified in Ggt -infected wheat roots, while 2,011 DEGs were detected in Bv + Ggt -infected roots, relative to the Ggt grown on PDA plates. Moreover, 31 DEGs were identified between wheat roots, respectively infected with Ggt and Bv + Ggt , consisting of 29 downregulated genes coding for potential Ggt pathogenicity factors – e.g., para-nitrobenzyl esterase, cutinase 1 and catalase-3, and two upregulated genes coding for tyrosinase and a hypothetical protein in the Bv + Ggt -infected roots when compared with the Ggt -infected roots. In particular, the expression of one gene, encoding the ABA3 involved in the production of Ggt ’s hormone abscisic acid, was 4.11-fold lower in Ggt -infected roots with Bv than without Bv . This is the first experimental study to analyze the activity of Ggt transcriptomes in wheat roots exposed or not to a biocontrol bacterium. Our results therefore suggest the presence of Bv directly and/or indirectly impairs the pathogenicity of Ggt in wheat roots through complex regulatory mechanisms, such as hyphopodia formation, cell wall hydrolase, and expression of a papain inhibitor, among others, all which merit further investigation.

pH effect on strain-specific transcriptomes of the take-all fungus

“…An aminotransferase was also overexpressed in G . tritici grown on PDA medium [ 37 ]. Concerning the genes driving the ‘oxydoreductase activity’ enrichment ( S8B Table ), study in Magnaporthe oryzae showed that the methylmalonate-semialdehyde dehydrogenase regulated pathogenesis [ 38 ].…”

“…Moreover, G. tritici transcriptomics study in host plant grown in soils of different pH would be interesting to focus more precisely on the infection stage. At this time indeed, only one transcriptomics studies were performed in G. tritici [37,53], and one highlighted that over 3,000 genes (including genes involved in signal transduction pathways, development, plant cell wall degradation, and response to plant defense compounds) were differentially expressed between G. tritici in culture and G. tritici infecting roots, but this study is based on a single strain not characterized for G1/G2 type [53].…”

“…At this time indeed, only one transcriptomics studies were performed in G . tritici [ 37 , 53 ], and one highlighted that over 3,000 genes (including genes involved in signal transduction pathways, development, plant cell wall degradation, and response to plant defense compounds) were differentially expressed between G . tritici in culture and G .…”

“…In order to survive in different and rapidly changing environments, the fungi must indeed be able to adapt via their expression of genes for amino acid metabolism since amino acids constitute key sources of nitrogen for growth of many fungi. An aminotransferase was also overexpressed in G. tritici grown on PDA medium [37]. Concerning the genes driving the 'oxydoreductase activity' enrichment (S8B Table), study in Magnaporthe oryzae showed that the methylmalonate-semialdehyde dehydrogenase regulated pathogenesis [38].…”

Cell-Free Fermentation Broth of Bacillus velezensis Strain S3-1 Improves Pak Choi Nutritional Quality and Changes the Bacterial Community Structure of the Rhizosphere Soil

“…B. velezensis can produce volatile organic compounds (VOCs), iturin, fengycin, surfactin, and antibiotics, among others, to inhibit fungal growth (Jin et al, 2017). Bacteria can also inhibit the growth of fungi by altering the gene expression of the fungus (Kang et al, 2019). At the same time, bacteria can produce indole acetic acid (IAA), siderophore, and phosphorus solubilization to promote plant growth (Kim et al, 2017).…”