Verticillium dahliaeLysM effectors differentially contribute to virulence on plant hosts

Abstract

SUMMARYChitin-binding LysM effectors contribute to virulence of various plant pathogenic fungi that are causal agents of foliar diseases. Here, we report on LysM effectors of the soil-borne fungal vascular wilt pathogen Verticillium dahliae. Comparative genomics revealed three core LysM effectors that are conserved in a collection of V. dahliae strains. Remarkably, and in contrast to the previously studied LysM effectors of other plant pathogens, no expression of core LysM effectors was monitored in planta in a taxonomically diverse panel of host plants. Moreover, targeted deletion of the individual LysM effector genes in V. dahliae strain JR2 did not compromise virulence in infections on Arabidopsis, tomato or Nicotiana benthamiana. Interestingly, an additional lineage-specific LysM effector is encoded in the genome of V. dahliae strain VdLs17 but not in any other V. dahliae strain sequenced to date. Remarkably, this lineage-specific effector is expressed in planta and contributes to virulence of V. dahliae strain VdLs17 on tomato, but not on Arabidopsis or on N. benthamiana. Functional analysis revealed that this LysM effector binds chitin, is able to suppress chitin-induced immune responses, and protects fungal hyphae against hydrolysis by plant hydrolytic enzymes. Thus, in contrast to the core LysM effectors of V. dahliae, this lineage-specific LysM effector of strain VdLs17 contributes to virulence in planta.

A lysin motif effector subverts chitin‐triggered immunity to facilitate arbuscular mycorrhizal symbiosis

“…Fungal LysM effectors from pathogens have been found to either protect fungal cell walls from apoplastic chitinases or to suppress chitin‐triggered immunity, with some LysM effectors possessing both activities to support fungal infection (de Jonge et al , ; Marshall et al , ; Mentlak et al , ; Lee et al , ; Kombrink et al , ). To test whether RiSLM has the ability to protect against plant chitinases, we tested the effect of RiSLM on hyphal integrity of T. viride and F. oxysporum f. sp.…”

“…S3a). These bands may reflect oligomers of RiSLM, as was previously observed for the Slp1 LysM effector from M. oryzae and Vd2LysM from V. dahliae (Mentlak et al, 2012;Kombrink et al, 2017). We first tested the ability of the purified RiSLM protein to bind chitin using affinity precipitation assays with the insoluble carbohydrates chitin, chitosan, xylan, and cellulose.…”

TheRhizoctonia solaniRsLysM and RsRlpA effector proteins contribute to virulence by suppressing chitin-triggered immunity and hypersensitive response

“…In parallel have numerous LysM receptors been identified for example one that binds to nodulation factors important for nodule development in legumes and thereby promote nitrogen fixation (Broghammer et al, 2012). In plant -pathogen interactions, a wealth of knowledge on LysM derives from pathogenic fungal species, (de Jonge et al, 2010;Marshall et al, 2011;Mentlak et al, 2012;Kombrink et al, 2017).…”

“…To investigate whether the RsLysM effector also prevent plant chitin-triggered immunity, N. benthamiana leaves were treated with chitin oligomers (GlcNAc) 6 , which led to reactive oxygen species (ROS) burst (Figure 6B), suggesting that RsLysM displays similar non-recognition function as seen in other pathosystems. Certain LysM effectors are able to protect fungal hyphae from chitinolytic activity (Marshall et al, 2011;Kombrink et al, 2017) similar to the Avr4 effector from C. fulvum (van den Burg et al, 2006). To investigate whether the RsLysM displays similar function, germinated conidia from T. viride were mixed with pure RsLysM protein, while Avr4 and BSA were used as positive and negative controls respectively.…”

Tools of the crook‐ infection strategies of fungal plant pathogens

“…As opposed to LysMs, Avr4 binds chitin through an invertebrate chitin-binding module to protect the cell wall against hydrolysis by host enzymes (van den Burg et al, 2006;van Esse et al, 2007). In contrast to Avr4 homologues that only occur in a limited set of fungi that are closely related to C. fulvum (Stergiopoulos et al, 2010), LysM effector proteins occur in a wide variety of fungi (de Jonge and Thomma, 2009), and have been shown to suppress chitin-triggered immunity on various plant hosts such as for Z. tritici on wheat (Marshall et al, 2011), for M. oryzae on rice (Mentlak et al, 2012), for Colletotrichum higginsianum on Arabidopsis (Takahara et al, 2016), and for Verticillium dahliae on tomato (Kombrink et al, 2017).…”