Kemen, A. | bioRxiv Science

bioRxiv2026

Intrinsic disorder in elicitin-like effectors: Molecular shields in the arms race of biotrophic pathogens

Plant pathogens establish colonization through effector secretion to modulate host immune responses. Within bacterial effectors intrinsically disordered regions (IDRs) contribute to diverse functions and pathogenicity, but their role in effectors of phytopathogenic oomycetes remains poorly understood. Here, analysis of oomycete secretomes across lifestyles reveal widespread intrinsic disorder in secreted proteins, particularly in apoplastic elicitin and elicitin-like effectors (ELLs). Combining in vitro and in planta experiments, we show that IDRs in ELLs from the biotrophic pathogen Albugo candida reduce immune recognition, consistent with an IDR-mediated shielding mechanism. This function is transferable, as fusion of an ELL-derived IDR to the immunogenic elicitin INF1 from Phytophthora infestans abolishes its recognition. These findings identify intrinsic disorder as a functional feature of apoplastic effectors that modulates host detection and promotes pathogen fitness. Graphical summary O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/717489v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@1363e05org.highwire.dtl.DTLVardef@21f34dorg.highwire.dtl.DTLVardef@ec6e5borg.highwire.dtl.DTLVardef@41327b_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2022

Proteins released into the plant apoplast by the obligate parasitic protist Albugo selectively repress phyllosphere-associated bacteria

Biotic and abiotic interactions shape natural microbial communities. The mechanisms behind microbe-microbe interactions, particularly those protein-based, are not well understood. We hypothesize that secreted proteins are a powerful and highly specific toolset to shape and defend plant niches. We have studied Albugo candida, an obligate plant parasite from the protist Oomycota phylum, for its potential to modulate the growth of bacteria through secretion of proteins into the apoplast. Amplicon sequencing and network analysis of Albugo-infected and uninfected samples revealed an abundance of negative correlations between Albugo and other phyllosphere microbes. Analysis of the apoplastic proteome of Albugo colonized leaves combined with machine-learning predictors enabled the selection of candidates for heterologous expression and study of their inhibitory activity. We found that three of the candidate proteins show selective antimicrobial activity on gram-positive bacteria isolated from Arabidopsis thaliana and that these inhibited bacteria are important for the stability of the community structure. We could ascribe the antibacterial activity of the candidates to intrinsically disordered regions and positively correlate it with net charge. This is the first report of protist proteins with antimicrobial activity under apoplastic conditions that therefore are potential biocontrol tools for targeted manipulations of the microbiome.

microbiology↗