Toxin-Antitoxin Systems: Implications for Plant Disease

Abstract

Toxin-antitoxin (TA) systems are gene modules that are ubiquitous in free-living prokaryotes. Diverse in structure, cellular function, and fitness roles, TA systems are defined by the presence of a toxin gene that suppresses bacterial growth and a toxin-neutralizing antitoxin gene, usually encoded in a single operon. Originally viewed as DNA maintenance modules, TA systems are now thought to function in many roles, including bacterial stress tolerance, virulence, phage defense, and biofilm formation. However, very few studies have investigated the significance of TA systems in the context of plant-microbe interactions. This review discusses the potential impact and application of TA systems in plant-associated bacteria, guided by insights gained from animal-pathogenic model systems.

Integrity and stability of virulence plasmids fromPseudomonas syringaeare modulated by mobile genetic elements and multiple toxin-antitoxin systems

“…It is also noteworthy that most of these plasmids possess several TA systems, as occurs with plasmids from other bacteria (see also Fig. 6) [4,57,58].…”

“…Nevertheless, and although we observed similar transposition frequencies of IS801 in two different strains [22], we cannot discount the possibility that these frequencies would be variable among different pathovars or species. Third, and although largely ignored, TA systems are increasingly being found associated to native plasmids in many diverse plant pathogens, including P. syringae [20,58,59]. It is also noteworthy that most of these plasmids possess several TA systems, as occurs with plasmids from other bacteria (see also Fig.…”

Identification of the Calmodulin-dependent NAD+kinase sustaining the elicitor-induced oxidative burst in plants

“…Type II zeta toxins-epsilon antitoxins systems are pairs of self-poisoning agents and their antidotes, which are common in Archaea and Bacteria, but rare in Eukaryotes (Yamaguchi et al, 2011). Possible roles of zeta toxins in plant virulence were recently revealed (Shidore and Triplett, 2017). Notably, the Xanthomonas AvrRxol zeta toxin is injected in plant cells during infections and is able to block the plant’s oxidative burst and its pathogen response (Shidore et al, 2017) by hijacking NAD metabolism via the production of the toxic compound 3’NADP.…”

“…Possible roles of zeta toxins in plant virulence were recently revealed (Shidore and Triplett, 2017). Notably, the Xanthomonas AvrRxol zeta toxin is injected in plant cells during infections and is able to block the plant’s oxidative burst and its pathogen response (Shidore et al, 2017) by hijacking NAD metabolism via the production of the toxic compound 3’NADP.…”

Genome Insights of the Plant-Growth Promoting Bacterium Cronobacter muytjensii JZ38 With Volatile-Mediated Antagonistic Activity Against Phytophthora infestans

“…The toxins are believed to slow down (dormancy) or suppress growth (cell death) in order to survive in rapidly changing environments or stress conditions (Gerdes et al, 1986;Yamaguchi and Inouye, 2009). TA systems have other diverse functions and roles, including ensuring persistence of plasmids during replication, virulence, antibiotic tolerance, phage defense and biofilm formation (Hayes, 2003;Sass et al, 2014;Shidore and Triplett, 2017). A number of genes related to different classes of TA systems were found in JZ38 ( Supplementary Table S16), including an adenylate cyclase toxin (cyaA) (Cannella et al, 2017), SOS-induced toxins (tisB, symE) and their regulator (lexA) (Gerdes and Wagner, 2007), membrane stress phage shock proteins (pspABCD) (Engl et al, 2010), toxins involved in cell division (cptAB, fstZ, merB) (Masuda et al, 2012) cell death (phd, doc, clpXP) (Smith and Magnuson, 2004), promoters of persister cells (hha-tomB, hipAB in plasmid p2).…”