Degradation of aromatic compounds through the β‐ketoadipate pathway is required for pathogenicity of the tomato wilt pathogen Fusarium oxysporum f. sp. lycopersici

Abstract

Summary Plant roots react to pathogen attack by the activation of general and systemic resistance, including the lignification of cell walls and increased release of phenolic compounds in root exudate. Some fungi have the capacity to degrade lignin using ligninolytic extracellular peroxidases and laccases. Aromatic lignin breakdown products are further catabolized via the β‐ketoadipate pathway. In this study, we investigated the role of 3‐carboxy‐cis,cis‐muconate lactonizing enzyme (CMLE), an enzyme of the β‐ketoadipate pathway, in the pathogenicity of Fusarium oxysporum f. sp. lycopersici towards its host, tomato. As expected, the cmle deletion mutant cannot catabolize phenolic compounds known to be degraded via the β‐ketoadipate pathway. In addition, the mutant is impaired in root invasion and is nonpathogenic, even though it shows normal superficial root colonization. We hypothesize that the β‐ketoadipate pathway in plant‐pathogenic, soil‐borne fungi is necessary to degrade phenolic compounds in root exudate and/or inside roots in order to establish disease.

Hydroxycinnamic Acid Degradation, a Broadly Conserved Trait, ProtectsRalstonia solanacearumfrom Chemical Plant Defenses and Contributes to Root Colonization and Virulence

“…Pseudomonas syringae uses type III effectors to manipulate plant phenylpropanoids (Truman et al, 2006). Many plant pathogens protect themselves with drug efflux pumps, while others enzymatically degrade the plant defense compounds pisatin, tomatine, and HCAs (Tegtmeier and VanEtten, 1982; Tegos et al, 2002; Brown et al, 2007; Seipke and Loria, 2008; Michielse et al, 2012). Our results support a general model that root-infecting pathogens encounter toxic concentrations of HCAs, and that degradation of these defenses is important for pathogenic success.…”

Microbial Biotreatment of Actual Textile Wastewater in a Continuous Sequential Rice Husk Biofilter and the Microbial Community Involved

“…This group of fungi has a documented ability to degrade polycyclic aromatic hydrocarbons (PAHs) [53]. For example Fusarium oxysporum utilize the β-ketoadipate pathway to degrade aromatic compounds [54]. Also, we detected three members of Tremellaceae known to carry enzymes, e.g.…”

“…Also, we detected three members of Tremellaceae known to carry enzymes, e.g. laccases, particularly suitable for degradation of aromatic compounds [54]. Furthermore, Basidomycota include several white-rot fungi, such as Bjerkandera , Trametes versicolor , Pleurotus ostreatus , that have displayed a capability to degrade different dyes [14].…”

Biosynthesis of Silver Nanoparticles by Pathogenic and Nonpathogenic Strains of Fusarium oxysporum f. sp. lycopersici

“…The symmetric graph indicates the optimum conversion of silver ions to SNPs which may be due to the secretion of nitrate reductase, an enzyme responsible for the reduction of silver ions. Proteins have multiple effects on the dispersion, including potential screening of the surface charges that help to maintain the repulsion between the particles, or bridging type interactions (Michielse et al, 2012 andBirla et al, 2013).…”

“…Non-pathogenic strains of the same species are present in the rhizosphere soil and colonize plant roots, but seem not to invade the vascular system. F. oxysporum, can degrade lignin using ligninolytic extracellular peroxidases and laccase (Michielse et al, 2012).…”