The large, diverse, and robust arsenal of Ralstonia solanacearum type III effectors and their in planta functions

Abstract

The type III secretion system with its delivered type III effectors (T3Es) is one of the main virulence determinants of Ralstonia solanacearum, a worldwide devastating plant pathogenic bacterium affecting many crop species. The pan‐effectome of the R. solanacearum species complex has been exhaustively identified and is composed of more than 100 different T3Es. Among the reported strains, their content ranges from 45 to 76 T3Es. This considerably large and varied effectome could be considered one of the factors contributing to the wide host range of R. solanacearum. In order to understand how R. solanacearum uses its T3Es to subvert the host cellular processes, many functional studies have been conducted over the last three decades. It has been shown that R. solanacearum effectors, as those from other plant pathogens, can suppress plant defence mechanisms, modulate the host metabolism, or avoid bacterial recognition through a wide variety of molecular mechanisms. R. solanacearum T3Es can also be perceived by the plant and trigger immune responses. To date, the molecular mechanisms employed by R. solanacearum T3Es to modulate these host processes have been described for a growing number of T3Es, although they remain unknown for the majority of them. In this microreview, we summarize and discuss the current knowledge on the characterized R. solanacearum species complex T3Es.

Unravelling physiological signatures of tomato bacterial wilt and xylem metabolites exploited by Ralstonia solanacearum

“…On the other hand, R. solanacearum spp. relies on effectors delivered by the type-three secretion system to circumvent plant immunity (Landry et al, 2020) as well as many other virulence factors which contribute to pathogenic fitness at the different infection steps (Genin & Denny, 2012;Hikichi et al, 2017).…”

An NLR Integrated Domain toolkit to identify plant pathogen effector targets

“…We exploited our knowledge [27,36] and availability of a set of conserved Ralstonia solanacearum T3Es [6] cloned and readily available [29]. We used a Yeast-2-Hybrid mating strategy, as a quick and efficient method to screen for interactions between the collection of 31 cloned R. solanacearum T3Es and the library of 52 IDs clones.…”

“…In most cases, these are secreted or translocated proteins acting as virulence factors (effectors). In plant pathogenic bacteria, the type III secretion system (T3SS) enables the injection of type III effectors (T3Es) inside the host cell in order to subvert basal defence responses or to manipulate the host metabolism [5,6]. Resistant plants are genetically equipped to perceive specific T3Es.…”

Silencing SmD1 in Solanaceae alters susceptibility to root-knot nematodes

“…The identification of conserved effectors could lead to new strategies for developing broad resistance (Huang et al , 2006; Landry et al , 2020; Peeters et al , 2013; Roux et al , 2015). Only a few RKN effectors have been described to be conserved.…”