Abstract
Methyl gallate (MG) is an effective microbicide with great potential application in the integrated management of plant diseases and an important potential drug for clinical application. However, its target remains unknown. This study conducted a transposon sequencing (Tn-seq) under MG treatment in plant pathogenic bacterium Ralstonia solanacearum. Tn-seq identified that the mutation of caseinolytic protease proteolytic subunit gene clpP significantly increased the resistance of R. solanacearum to MG, which was validated by the in-frame gene deletion. iTRAQ (isobaric tags for relative and absolute quantitation) proteomics analysis revealed that chemotaxis and flagella associated proteins were the major substrates degraded by ClpP under the tested condition. Moreover, sulfur metabolism-associated proteins were potential substrates of ClpP and were upregulated by MG treatment in wild-type R. solanacearum but not in clpP mutant. Furthermore, molecular docking confirmed the possible interaction between MG and ClpP. Collectively, this study revealed that MG might target bacterial ClpP, inhibit the activity of ClpP, and consequently disturb bacterial proteostasis, providing a theoretical basis for the application of MG.
Highlights
Methyl gallate (MG) is a well-studied polyphenolic compound, which is isolated from many plants, such as Toxicodendron sylvestre (Yuan et al, 2012), Tamarix nilotica (Orabi et al, 2020), baru (Dipteryx alata Vog.) (Oliveira-Alves et al, 2020), and walnuts (Juglans regia L.) (Zhang et al, 2020)
The MG-treated and untreated transposon insertion libraries were subjected to Illumina sequencing and bioinformatics analysis to identify the relative abundance of each insertion mutant
The transposon insertion within MG target genes would increase the relative abundance of R. solanacearum under MG treatment
Summary
Methyl gallate (MG) (methyl 3,4,5-trihydroxybenzoate) is a well-studied polyphenolic compound, which is isolated from many plants, such as Toxicodendron sylvestre (Yuan et al, 2012), Tamarix nilotica (Orabi et al, 2020), baru (Dipteryx alata Vog.) (Oliveira-Alves et al, 2020), and walnuts (Juglans regia L.) (Zhang et al, 2020). MG is an effective microbicide, which shows great potential application in the integrated management of plant diseases, such as tomato bacterial wilt caused by Ralstonia solanacearum (Yuan et al, 2012) and rice blast caused by Magnaporthe grisea (Ahn et al, 2005). MG is an important potential drug for clinical application. MG effectively inhibits the adhesion, invasion, and intracellular survival of Salmonella typhimurium (Birhanu et al, 2018). MG inhibits oral bacterial growth and the formation of Streptococcus mutans biofilm (Kang et al, 2008). Recent virtual screening has shown that MG is a potential ligand binding the NSP10/NSP16 methyltransferase of coronavirus disease 2019 (COVID-19) (Maurya et al, 2020).
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