bak1-5 mutation uncouples tryptophan-dependent and independent postinvasive immune pathways triggered in Arabidopsis by multiple fungal pathogens

ABSTRACTRobust nonhost resistance of Arabidopsis thaliana against the nonadapted hemibiotrophic fungus Colletotrichum tropicale requires PEN2-dependent preinvasive and CYP71A12/CYP71A13-dependent postinvasive resistance, which both rely on tryptophan (Trp) metabolism. Here we report that CYP71A12 and CYP71A13 are critical for Arabidopsis’ postinvasive resistance toward both the necrotrophic Alternaria brassicicola and the adapted hemibiotrophic C. higginsianum fungi. Metabolite analyses suggest that the production of indole-3-carboxylic acid derivatives (ICAs) and camalexin is induced upon pathogen invasion, while phenotypic comparison of cyp79B2 cyp79B3 and pen2 cyp71A12 cyp71A13 plants indicates that the contribution of ICAs to postinvasive resistance is dose-dependent. We also found that the disruption of intact pattern recognition receptor complex caused by bak1–5 mutation significantly reduced postinvasive resistance against C. tropicale and A. brassicicola, indicating that pattern recognition commonly contributes to this second defense-layer against pathogens with distinct infection strategies. However, the bak1–5 mutation had no detectable effects on Trp-metabolite accumulation triggered by pathogen invasion. Together with this, further comparative gene expression analyses suggested that pathogen invasion in Arabidopsis activates (i) bak1–5 insensitive Trp-metabolism that leads to antimicrobial secondary metabolites, and (ii) a bak1–5 sensitive immune pathway that activates the expression of antimicrobial proteins.

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Tryptophan-derived metabolites and BAK1 separately contribute to Arabidopsis postinvasive immunity against Alternaria brassicicola

Scientific Reports ◽

10.1038/s41598-020-79562-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ayumi Kosaka ◽

Marta Pastorczyk ◽

Mariola Piślewska-Bednarek ◽

Takumi Nishiuchi ◽

Erika Ono ◽

...

Keyword(s):

Gene Expression ◽

Arabidopsis Thaliana ◽

Alternaria Brassicicola ◽

Nonhost Resistance ◽

Antimicrobial Proteins ◽

Basal Resistance ◽

Pathogen Invasion ◽

Gene Expression Analyses ◽

Colletotrichum Tropicale ◽

Immune Pathway

AbstractNonhost resistance of Arabidopsis thaliana against the hemibiotrophic fungus Colletotrichum tropicale requires PEN2-dependent preinvasive resistance and CYP71A12 and CYP71A13-dependent postinvasive resistance, which both rely on tryptophan (Trp) metabolism. We here revealed that CYP71A12, CYP71A13 and PAD3 are critical for Arabidopsis’ postinvasive basal resistance toward the necrotrophic Alternaria brassicicola. Consistent with this, gene expression and metabolite analyses suggested that the invasion by A. brassicicola triggered the CYP71A12-dependent production of indole-3-carboxylic acid derivatives and the PAD3 and CYP71A13-dependent production of camalexin. We next addressed the activation of the CYP71A12 and PAD3-dependent postinvasive resistance. We found that bak1-5 mutation significantly reduced postinvasive resistance against A. brassicicola, indicating that pattern recognition contributes to activation of this second defense-layer. However, the bak1-5 mutation had no detectable effects on the Trp-metabolism triggered by the fungal penetration. Together with this, further comparative gene expression analyses suggested that pathogen invasion in Arabidopsis activates (1) CYP71A12 and PAD3-related antifungal metabolism that is not hampered by bak1-5, and (2) a bak1-5 sensitive immune pathway that activates the expression of antimicrobial proteins.

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Cnidarian Pattern Recognition Receptor Repertoires Reflect Both Phylogeny and Life History Traits

Frontiers in Immunology ◽

10.3389/fimmu.2021.689463 ◽

2021 ◽

Vol 12 ◽

Author(s):

Madison A. Emery ◽

Bradford A. Dimos ◽

Laura D. Mydlarz

Keyword(s):

Pattern Recognition ◽

Innate Immunity ◽

Life History ◽

Life History Traits ◽

Innate Immune ◽

Immune Pathways ◽

Immune Pathway ◽

Molecular Patterns ◽

Insight Into ◽

Recognition Receptor

Pattern recognition receptors (PRRs) are evolutionarily ancient and crucial components of innate immunity, recognizing danger-associated molecular patterns (DAMPs) and activating host defenses. Basal non-bilaterian animals such as cnidarians must rely solely on innate immunity to defend themselves from pathogens. By investigating cnidarian PRR repertoires we can gain insight into the evolution of innate immunity in these basal animals. Here we utilize the increasing amount of available genomic resources within Cnidaria to survey the PRR repertoires and downstream immune pathway completeness within 15 cnidarian species spanning two major cnidarian clades, Anthozoa and Medusozoa. Overall, we find that anthozoans possess prototypical PRRs, while medusozoans appear to lack these immune proteins. Additionally, anthozoans consistently had higher numbers of PRRs across all four classes relative to medusozoans, a trend largely driven by expansions in NOD-like receptors and C-type lectins. Symbiotic, sessile, and colonial cnidarians also have expanded PRR repertoires relative to their non-symbiotic, mobile, and solitary counterparts. Interestingly, cnidarians seem to lack key components of mammalian innate immune pathways, though similar to PRR numbers, anthozoans possess more complete immune pathways than medusozoans. Together, our data indicate that anthozoans have greater immune specificity than medusozoans, which we hypothesize to be due to life history traits common within Anthozoa. Overall, this investigation reveals important insights into the evolution of innate immune proteins within these basal animals.

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