Biology subjects

Bednarek, P.

Publications and source records attributed to Bednarek, P..

7 recordsLinked to original sources

bioRxiv2026

Loss of a conserved disulfide bond defines Penetration2-related immune myrosinases in Brassicaceae

O_LIThis study investigated whether PEN2/BGLU26 has uniquely evolved as an indole glucosinolate-hydrolysing myrosinase required for Arabidopsis thaliana pre-invasive immunity, or whether related myrosinases can replace its function when targeted to the same subcellular context. C_LIO_LIPEN2-homologous and other selected myrosinases from A. thaliana and Brassica rapa were expressed in the pen2-2 mutant background using a PEN2-like targeting strategy. The resulting lines were assessed by gene expression, protein accumulation, metabolite analysis and pathogen resistance assays. In parallel, targeted mutagenesis, structural comparison and phylogenetic analysis were used to examine molecular and evolutionary features of PEN2-related myrosinases. C_LIO_LIAtBGLU27 and BrBABG.a, but not AtBGLU18, AtBGLU23 or AtBGLU28, partially restored indole glucosinolate hydrolysis and resistance to Colletotrichum tropicale in pen2-2. Unlike AtPEN2, both enzymes acted mainly constitutively and showed distinct substrate preferences. PEN2, BGLU27 and BABG proteins lacked conserved post-translational modification sites, including residues associated with a conserved disulfide bond. Restoring this disulfide bond in AtPEN2 abolished its activity. C_LIO_LIPEN2-related myrosinases form an evolutionarily distinct BGLU lineage associated with indole glucosinolate metabolism in Brassicales. Loss of the conserved disulfide bond appears to be required for PEN2 activity, whereas additional PEN2-specific regulatory features are needed for pathogen-triggered, rather than constitutive, glucosinolate metabolism. C_LI

plant biology↗

bioRxiv2023

ATML1 Regulates the Differentiation of ER Body-containing Large Pavement Cells in Rosette Leaves of Brassicaceae Plants

Endoplasmic reticulum (ER)-derived organelles, ER bodies, participate in the defense against herbivores in Brassicaceae plants. ER bodies accumulate {beta}-glucosidases, which hydrolyse specialized thioglucosides known as glucosinolates to generate bioactive substances. In Arabidopsis thaliana, the leaf ER (LER) bodies are formed in large pavement cells, which are found in the petioles, margins, and blades of rosette leaves. However, the regulatory mechanisms involved in establishing large pavement cells are unknown. Here, we show that the ARABIDOPSIS THALIANA MERISTEM L1 LAYER (ATML1) transcription factor regulates the formation of LER bodies in large pavement cells of rosette leaves. Overexpression of ATML1 enhanced the expression of LER body-related genes and the number of LER body-containing large pavement cells, whereas its knockout resulted in opposite effects. ATML1 enhances endoreduplication and cell size through LOSS OF GIANT CELLS FROM ORGANS (LGO). Although the overexpression and knockout of LGO affected the appearance of large pavement cells in Arabidopsis, the effect on LER body-related gene expression and LER body formation was weak. LER body-containing large pavement cells were also found in Eutrema salsugineum, another Brassicaceae species. Our results demonstrate that ATML1 establishes large pavement cells to induce LER body formation in Brassicaceae plants, contributing to the defense against herbivores.

plant biology↗

bioRxiv2022

Tryptophan specialized metabolism and ER body-resident myrosinases modulate root microbiota assembly

Indole glucosinolates (IGs) are tryptophan (Trp)-derived sulfur-containing specialized metabolites that play a crucial role in plant-microbe interactions in plants of the order Brassicales, including Arabidopsis thaliana. Despite the growing body of evidence implicating IG biosynthetic pathways in root-microbiota interactions, how myrosinases, the enzymes that convert inert IGs into bioactive intermediate/terminal products, contribute to this process remains unknown. Here, we describe the roles of the PYK10 and BGLU21 myrosinases in root-microbiota assembly partly via metabolites secreted from roots into the rhizosphere. PYK10 and BGLU21 localize to the endoplasmic reticulum (ER) body, an ER-derived organelle observed in plants of the family Brassicaceae. We investigated the root microbiota structure of mutants defective in the Trp metabolic (cyp79b2b3 and myb34/51/122) and ER body (nai1 and pyk10bglu21) pathways and found that these factors together contribute to the assembly of root microbiota. Microbial community composition in soils as well as in bacterial synthetic communities (SynComs) treated with root exudates axenically collected from pyk10bglu21 and cyp79b2b3 differed significantly from those treated with exudates derived from wild-type plants, pointing to a direct role of root-exuded compounds. We also show that growth of the pyk10bglu21 and cyp79b2b3 mutants was severely inhibited by fungal endophytes isolated from healthy A. thaliana plants. Overall, our findings demonstrate that root ER body-resident myrosinases influencing the secretion of Trp-derived specialized metabolites represent a lineage-specific innovation that evolved in Brassicaceae to regulate root microbiota structure. SignificanceER bodies were first identified in roots of Brassicaceae plants more than 50 years ago, but their physiological functions have remained uncharacterized. A series of previous studies have suggested their possible role in root-microbe interactions. Here, we provide clear experimental evidence showing a role for ER bodies in root-microbiota interactions, which overlaps with that of root-exuded Trp-derived metabolites. Our findings delineate a plant lineage-specific innovation involving intracellular compartments and metabolic enzymes that evolved to regulate plant-microbe interactions at the root-soil interface.

plant biology↗

bioRxiv2022

Loss of MYB34 transcription factor that controls feedback loop in indole glucosinolate biosynthesis supports backward evolution of this pathway within Camelineae tribe

Glucosinolates are specialized defensive metabolites characteristic for the Brassicales order. Among them aliphatic and indolic glucosinolates (IGs) are usually highly abundant in the species from Brassicaceae family. The exception from this trend is constituted by species representing a subclade of Camelineae tribe, including Capsella and Camelina genera, which have reduced capacity to produce and metabolize IGs. Our study addresses contribution of specific glucosinolate-related MYB transcription factors to this unprecedented backward evolution of IG biosynthesis. To this end we performed phylogenomic and functional studies of respective MYB proteins. Obtained results revealed weakened conservation of glucosinolate-related MYB transcription factors, including loss of functional MYB34 protein, in the investigated species. We showed that introduction of functional MYB34 from Arabidopsis thaliana partially restores IG biosynthesis in Capsella rubella indicating that loss of this transcription factor contributes to the backward evolution of this metabolic pathway. Finally, we performed analysis of the impact of particular myb mutations on the feedback loop in IG biosynthesis, which drives auxin overproduction, metabolic dysregulation and strong growth retardation caused by mutations in IG biosynthetic genes. This uncovered unique function of MYB34 among IG-related MYBs in this feedback regulation and consequently in IG conservation in Brassicaceae plants.

plant biology↗

bioRxiv2020

Gene expression evolution in pattern-triggered immunity within Arabidopsis thaliana and across Brassicaceae species

Plants recognize surrounding microbes by sensing microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI). Despite their significance for microbial control, the evolution of PTI responses remains largely uncharacterized. Employing comparative transcriptomics of six Arabidopsis thaliana accessions and three additional Brassicaceae species for PTI responses to the MAMP flg22, we identified a set of genes with expression changes under purifying selection in the Brassicaceae species and genes exhibiting species-specific expression signatures. Variation in flg22-triggered transcriptome and metabolome responses across Brassicaceae species was incongruent with their phylogeny while expression changes were strongly conserved within A. thaliana, suggesting directional selection for some species-specific gene expression. We found the enrichment of WRKY transcription factor binding sites in 5-regulatory regions in conserved and species-specific responsive genes, linking the emergence of WRKY-binding sites with the evolution of gene responses in PTI. Our findings advance our understanding of transcriptome evolution during biotic stress.

plant biology↗

bioRxiv2020

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

Robust 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.

plant biology↗

bioRxiv2019

Arabidopsis phytochelatin synthase 1, but not phytochelatin synthesis, functions in extracellular defense against multiple fungal pathogens

Phytochelatin synthase (PCS) is a key component of heavy metal detoxification in plants. PCS catalyzes both the synthesis of the peptide phytochelatin from glutathione as well as the degradation of glutathione conjugates via peptidase activity. Here, we describe a hitherto uncharacterized role for PCS in disease resistance against plant pathogenic fungi. The pen4 mutant, which is allelic to cadmium insensitive 1 (cad1/pcs1) mutants, was recovered from a screen for Arabidopsis mutants with reduced resistance to the non-adapted barley fungal pathogen, Blumeria graminis f. sp. hordei. PCS1, which is found in the cytoplasm of cells of healthy plants, translocates upon pathogen attack and colocalizes with the PEN2 myrosinase on the surface of immobilized mitochondria. pcs1 and pen2 mutant plants exhibit a similar metabolic defect in the accumulation of pathogen-inducible indole glucosinolate-derived compounds, suggesting that PEN2 and PCS1 act in the same metabolic pathway. The function of PCS1 in this pathway is independent of phytochelatin synthesis and deglycination of glutathione conjugates, as catalytic-site mutants of PCS1 are still functional in indole glucosinolate metabolism. In uncovering a previously unknown function for PCS1, we reveal this enzyme to be a moonlighting protein important for plant responses to both biotic and abiotic stresses.

plant biology↗