A Phakopsora pachyrhizi Effector Suppresses PAMP-Triggered Immunity and Interacts with a Soybean Glucan Endo-1,3-ß-Glucosidase to Promote Virulence.

Asian soybean rust, caused by the fungus Phakopsora pachyrhizi, is one of the most important diseases affecting soybean production in tropical areas. During infection, P. pachyrhizi secretes proteins from haustoria that are transferred into plant cells to promote virulence. To date, only one candidate P. pachyrhizi effector protein has been characterized in detail to understand the mechanism by which it suppresses plant defenses to enhance infection. Here, we aimed to extend understanding of the pathogenic mechanisms of P. pachyrhizi based on the discovery of host proteins that interact with the effector candidate Phapa-7431740. We demonstrated that Phapa-7431740 suppresses pathogen-associated molecular pattern-triggered immunity (PTI) and that it interacts with a soybean glucan endo-1,3-ß-glucosidase (GmßGLU), a pathogenesis-related (PR) protein belonging to the PR-2 family. Structural and phylogenetic characterization of the PR-2 protein family predicted in the soybean genome and comparison to PR-2 family members in Arabidopsis thaliana and cotton, demonstrated that GmßGLU is a type IV ß-1,3-glucanase. Transcriptional profiling during an infection time course showed that the GmßGLU mRNA is highly induced during the initial hours after infection, coinciding with peak of expression of Phapa-7431740. The effector was able to interfere with the activity of GmßGLU in vitro, with a dose-dependent inhibition. Our results suggest that Phapa-7431740 may suppress PTI by interfering with glucan endo-1,3-ß-glucosidase activity. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.

Microbiome-derived antimicrobial peptides offer therapeutic solutions for the treatment of Pseudomonas aeruginosa infections.

Microbiomes are rife for biotechnological exploitation, particularly the rumen microbiome, due to their complexicity and diversity. In this study, antimicrobial peptides (AMPs) from the rumen microbiome (Lynronne 1, 2, 3 and P15s) were assessed for their therapeutic potential against seven clinical strains of Pseudomonas aeruginosa. All AMPs exhibited antimicrobial activity against all strains, with minimum inhibitory concentrations (MICs) ranging from 4-512 µg/mL. Time-kill kinetics of all AMPs at 3× MIC values against strains PAO1 and LES431 showed complete kill within 10 min to 4 h, although P15s was not bactericidal against PAO1. All AMPs significantly inhibited biofilm formation by strains PAO1 and LES431, and induction of resistance assays showed no decrease in activity against these strains. AMP cytotoxicity against human lung cells was also minimal. In terms of mechanism of action, the AMPs showed affinity towards PAO1 and LES431 bacterial membrane lipids, efficiently permeabilising the P. aeruginosa membrane. Transcriptome and metabolome analysis revealed increased catalytic activity at the cell membrane and promotion of ß-oxidation of fatty acids. Finally, tests performed with the Galleria mellonella infection model showed that Lynronne 1 and 2 were efficacious in vivo, with a 100% survival rate following treatment at 32 mg/kg and 128 mg/kg, respectively. This study illustrates the therapeutic potential of microbiome-derived AMPs against P. aeruginosa infections.