A DEAD BOX RNA helicase fromMedicago truncatulais hijacked by an RNA-binding effector from the root pathogenAphanomyces euteichesto facilitate host infection

Abstract

26 Microbial effectors from plant pathogens are molecules that target host components to 27 facilitate colonization. While eukaryotic pathogens are virtually able to produce hundreds of 28 effectors, the molecular mechanisms allowing effectors to promote infection are still largely 29 unexplored. Here we show that the effector AeSSP1256 from the soilborne oomycete 30 pathogen Aphanomyces euteiches is able to interact with plant RNA. Heterologous expression 31 of AeSSP1256 delays Medicago truncatula host roots development and facilitate pathogen 32 colonization. Transcriptomic analyses of AeSSP1256-expressing roots show a downregulation 33 of genes implicated in ribosome biogenesis pathway. A yeast-two hybrid approach reveals 34 that AeSSP1256 associates with a nucleolar L7 ribosomal protein and a M. truncatula RNA 35 helicase (MtRH10) orthologous to the Arabidopsis RNA helicase RH10. Association of 36 AeSSP1256 with MtRH10 impaired the capacity of MtRH10 to bind nucleic acids. 37 Promoter:GUS composite plants revealed that MtRH10 is expressed preferentially in the 38 meristematic root cells. Missense MtRH10 plants displayed shorter roots with developmental 39 delay and are more susceptible to A. euteiches infection. These results show that the effector 40 AeSSP1256 facilitates pathogen infection by causing stress on plant ribosome biogenesis and 41 by hijacking a host RNA helicase involved in root development and resistance to root 42 pathogens. 43 105 ribosomal protein as interactors of AeSSP1256. By FRET-FLIM analyses we reveal that 106 AeSSP1256 co-opts MtRH10 to abolish its nucleic acid binding capacity. We provide a 107 mechanistic explanation of this observation by demonstrating the implication of MtRH10 in 108 roots development by generating missense and overexpressing Medicago lines. Finally we 109 5 observed that silenced-MtRH10 roots are highly susceptible to A. euteiches infection like 110 AeSSP1256-expressing roots, showing that MtRH10 as AeSSP1256 activities modify the 111 outcome of the infection. We now present results supporting effector-mediated manipulation 112 of a nuclear RNA helicase as a virulence mechanism during plant-eukaryotic pathogens 113 interactions.114 115 6 Results 116 117 AeSSP1256 contains RGG/RG domains and binds RNA in planta 118 AeSSP1256 is a member of a large family of A. euteiches effectors devoid of any predicted 119 functional domain, except the presence of a signal peptide at the N-terminus (Gaulin et al., 120 2018). As showed in Figure 1A, AeSSP1256 protein is enriched in glycine residues (30% of 121 the amino acid sequence). Analysis using the Eukaryotic Linear Motif database (Gouw et al., 122 2018) revealed 3 GGRGG motifs (positions 81-85; 95-99 and 99-103). These motifs are 123 variant arginine methylation site from arginine-glycine(-glycine) (RGG/RG) domains, 124 presents in many ribonucleoproteins and involved in RNA binding (Thandapani et al., 2013; 125 Bourgeois et al., 2020). We then noticed the presence of two di-RGG domains (RGG(X 0-126 5 )RGG) (position 75-85...

Pathogenicity of animal and plant parasitic Aphanomyces spp and their economic impact on aquaculture and agriculture

“…SSPs have also been detected in A. astaci. Functional studies have shown that SSPs from A. euteiches can target plant nuclei and modify activity of plant DEAD-box RNA helicase to enhance A. euteiches infection (Camborde et al, 2020). These effectors appear to be a promising area of research to improve our understanding of the molecular factors involved in the virulence of A. euteiches.…”