Pangenomic analysis reveals plant NAD⁺manipulation as an important virulence activity of bacterial pathogen effectors

Abstract

Nicotinamide adenine dinucleotide (NAD+) has emerged as a major component in both eukaryotic and prokaryotic immune systems. Recent findings that Toll/interleukin-1 receptor (TIR) proteins function as NAD+ hydrolases (NADase) link NAD+ metabolism with immune signaling. In this study, we investigated how manipulation of host NAD+ metabolism can be employed as a virulence strategy by pathogens. Using the pangenome of the model bacterial pathogen Pseudomonas syringae, we conducted a structure-based similarity search for type III effectors (T3Es) with potential NADase activity from 35,000 orthogroups. Thirteen T3Es, including five novel ones, were identified to possess domain(s) related to seven NAD+-hydrolyzing enzyme families. Most P. syringae strains encode at least one NAD+-manipulating T3Es, and many have multiple. We experimentally confirmed the type III-dependent secretion and virulence activity of a novel T3E, which shows similarity with both TIR and adenosine diphosphate ribose (ADPR) cyclase. Using AI-based structural prediction and in silico molecular docking, we found divergence at the NAD+-interacting positions and confirmed the functional importance of these residues in the TIR T3E HopAM1. This study highlights NAD+ manipulation as a key virulence mechanism and provides insights into how pathogens may promote infection through manipulation of host NAD+ metabolism.

Cyclic ADP ribose isomers: Production, chemical structures, and immune signaling

“…Bacterial and plant TIR domains produce cyclic signaling nucleotides with immune and virulence functions using NAD + or nucleic acids as substrates ( 14 , 15 , 21 , 22 , 26 , 32 , 33 , 38 – 40 ). Here, we report the chemical structures of two TIR domain–produced cADPR isomers, v-cADPR and v2-cADPR, which reveal that TIR domains can catalyze O-glycosidic bond formation between the ribose sugars in ADPR and that cyclization occurs at the 2′ (v-cADPR; 2′cADPR) and 3′ (v2-cADPR; 3′cADPR) positions of the adenosine ribose.…”

“…Bacterial and plant TIR domains produce cyclic signaling nucleotides with immune and virulence functions using NAD + or nucleic acids as substrates (14,15,21,22,26,32,33,(38)(39)(40).…”

Contrasting effector profiles between bacterial colonisers of kiwifruit reveal redundant roles and interplay converging on PTI-suppression and RIN4

“…While the plant targets of HopS2b are not known, a close ortholog of this effector from Pto DC3000 is a strong suppressor of ETI (Guo et al ., 2009). Recently, the HopS family of ADP-ribosyl transferases were identified as significant contributors to virulence and ETI suppression through activity as NADases (Hulin & Ma, 2022). HopAZ1a and HopS2b appear to be the only effectors present universally across the five Psa biovars and Pfm, suggesting they play an important role in kiwifruit plant colonisation (McCann et al ., 2013; Sawada & Fujikawa, 2019).…”

Activation and Regulation of NLR Immune Receptor Networks

“…It appears that 3'cADPR and its derivatives can manipulate ADR1/NRG1 network signalling (Manik et al, 2022). This host NAD + manipulation could be a conserved virulence mechanism of P. syringae, considering that 93% of the primary phylogroup P. syringae strains have at least one NADase effector (Hulin and Ma, 2022). Taken together, these findings indicate that plant pathogens have evolved effectors targeting NLR networks at multiple levels, thereby enabling them to establish infection and cause disease in the host.…”