Biology subjects

Wiermer, M.

Publications and source records attributed to Wiermer, M..

6 recordsLinked to original sources

bioRxiv2025

Two genetically linked Arabidopsis TIR-type NLRs are required for immunity and interact with NLRs encoded in a segmentally duplicated genomic region

Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors detect pathogen-secreted effectors inside host cells and induce a robust immune response, typically involving hypersensitive cell death. NLR genes are often genetically linked and can function as pairs or within larger NLR networks. We previously showed that the truncated Toll/Interleukin-1 Receptor (TIR)-type NLR TIR-NB13 (TN13) is required for resistance of Arabidopsis to Pseudomonas syringae pv. tomato (Pst) DC3000 lacking the type-III effector proteins AvrPto and AvrPtoB. TN13 is genetically linked to a full length TIR-NB-LRR (TNL) gene on chromosome 3. Here, we show that TN13, and its genetically linked TNL both localize to the ER membrane via N-terminal transmembrane domains, are required for resistance to Pst DC3000 ({Delta}AvrPto/AvrPtoB) and interact with each other in transient expression assays in Nicotiana benthamiana. In contrast to TN13, the full length TNL, which we named TN13-INTERACTING TNL1 (TNT1), induces an autoactive cell death response when expressed in N. benthamiana that depends on an atypical MHV motif in its NB-ARC domain, as well as the EDS1/SAG101/NRG1 module. TN13 and TNT1 furthermore interact with phylogenetically related NLRs encoded by a segmentally duplicated region on chromosome 5. Our data suggest that both TN13 and the genetically linked TNT1 could be part of a larger TIR-type NLR immune regulatory network, in which TNT1 contributes to basal immunity and might function as an autoactive death switch to induce cell death upon pathogen detection. SIGNIFICANCE STATEMENTThe ER membrane localized truncated TIR-NLR TN13 and the genomically linked full length TNL TNT1 are required for plant disease resistance and form heteromeric associations with phylogenetically related NLRs, encoded by a segmentally duplicated chromosomal region.

plant biology↗

bioRxiv2022

SLDP and LIPA mediate lipid droplet-plasma membrane tethering in Arabidopsis thaliana

Membrane contact sites (MCS) are inter-organellar connections that allow for the direct exchange of molecules, such as lipids or Ca2+ between organelles, but can also serve to tether organelles at specific locations within cells. Here we identified and characterised three proteins that form a lipid droplet (LD)-plasma membrane (PM) tethering complex in plant cells, namely LD-localised SEED LD PROTEIN (SLDP) 1 and 2 and PM-localised LD-PLASMA MEMBRANE ADAPTOR (LIPA). Using proteomics and different protein-protein interaction assays, we show that both SLDPs associate with LIPA. Disruption of either SLDP1 and 2 expression, or that of LIPA, leads to an aberrant clustering of LDs in Arabidopsis seedlings. Ectopic co-expression of one of the SLDPs with LIPA on the other hand is sufficient to reconstitute LD-PM tethering in Nicotiana tabacum pollen tubes, a cell type characterised by dynamically moving LDs in the cytosolic streaming. Further, confocal laser scanning microscopy revealed both SLDP2.1 and LIPA to be enriched at LD-PM contact sites in seedlings. These and other results suggest that SLDP and LIPA interact to form a tethering complex that anchors a subset of LDs to the PM during post-germinative seedling growth in Arabidopsis thaliana. One-sentence summarySEED LIPID DROPLET PROTEIN1 and 2 and LIPID DROPLET PLASMA MEMBRANE ADAPTOR tether lipid droplets to the plasma membrane in seedlings of Arabidopsis thaliana.

plant biology↗

bioRxiv2021

EXTRA LARGE G-PROTEIN 2 (XLG2) mediates cell death and hyperimmunity via a novel, apoplastic ROS-independent pathway in Arabidopsis thaliana

O_LIHeterotrimeric G-Proteins are signal transduction complexes comprised of three subunits, G, G{beta} and G{gamma}, and are involved in many aspects of plant life. The non-canonical G subunit XLG2 mediates PAMP-induced ROS generation and immunity downstream of PRRs. A mutant of the chitin receptor component CERK1, cerk1-4, maintains normal chitin signalling capacity, but shows excessive cell death upon infection with powdery mildews. We identified XLG2 mutants as suppressors of the cerk1-4 phenotype. C_LIO_LIWe generated stably transformed Arabidopsis lines expressing Venus-XLG2 and numerous mutated variants. These were analysed by confocal microscopy, Western blotting and pathogen infection. We also crossed cerk1-4 with several mutants involved in immunity and analysed their phenotype. Phosphorylation of XLG2 was investigated by quantitative proteomics. C_LIO_LIMutations in XLG2 complex partners AGB1 and AGG1 have a partial cerk1-4 suppressor effect. The cerk1-4 phenotype is independent of NADPH oxidase-generated ROS, BAK1 and SOBIR1, but requires PUB2. XLG2 mediates cerk1-4 cell death at the cell periphery. Integrity of the XLG2 N-terminal domain, but not its phosphorylation, is essential for correct XLG2 localisation and cerk1-4 signalling. C_LIO_LIOur results suggest that XLG2 transduces signals from an unknown cell surface receptor that activates an apoplastic ROS-independent cell death pathway in Arabidopsis. C_LI

plant biology↗

bioRxiv2020

Functional requirement of the Arabidopsis importin-α nuclear transport receptor family in autoimmunity mediated by the NLR protein SNC1

IMPORTIN-3/MOS6 (MODIFIER OF SNC1, 6) is one of nine importin- isoforms in Arabidopsis that recruit nuclear localization signal (NLS)-containing cargo proteins to the nuclear import machinery. IMP-3/MOS6 is required genetically for full autoimmunity of the nucleotide-binding leucine-rich repeat (NLR) immune receptor mutant snc1 (suppressor of npr1-1, constitutive 1) and MOS6 also contributes to basal disease resistance. Here, we investigated the contribution of the other importin- genes to both types of immune responses, and we analyzed potential interactions of all importin- isoforms with SNC1. By using reverse-genetic analyses in Arabidopsis and protein-protein interaction assays in N. benthamiana we provide evidence that among the nine -importins in Arabidopsis, IMP-3/MOS6 is the main nuclear transport receptor of SNC1, and that IMP-3/MOS6 is required selectively for autoimmunity of snc1 and basal resistance to mildly virulent Pseudomonas syringae in Arabidopsis. SIGNIFICANCE STATEMENTSpecific requirement for the Arabidopsis -importin MOS6 in snc1-mediated autoimmunity is explained by selective formation of MOS6-SNC1 nuclear import complexes.

plant biology↗

bioRxiv2019

The cell-wall-localised BETA-XYLOSIDASE 4 contributes to immunity of Arabidopsis against Botrytis cinerea

Plant cell walls constitute physical barriers that restrict access of microbial pathogens to the contents of plant cells. The primary cell wall of multicellular plants predominantly consists of cellulose, hemicellulose and pectin. In Arabidopsis, a cell wall-localised protein, BETA-XYLOSIDASE 4 (BXL4) that belongs to a seven-member BETA-XYLOSIDASE (BXL) gene family was induced upon infection with the necrotrophic fungal pathogen Botrytis cinerea and mechanical wounding in a jasmonoyl isoleucine (JA-Ile) dependent manner. Ectopic expression of the BXL4 gene in Arabidopsis seed coat epidermal cells was able to rescue a bxl1 mutant phenotype suggesting that like BXL1, BXL4, had both xylosidase and arabinosidase activity and acts in mura on cell wall polysaccharides. bxl4 mutants show a compromised resistance to B. cinerea. Upon infection, bxl4 mutants accumulated reduced levels of JA-Ile and camalexin. Conditional overexpression of BXL4 resulted in enhanced expression of PDF1.2 and PAD3 transcripts both before and after B. cinerea infection. This was associated with reduced susceptibility of the transgenic lines to B. cinerea. These data suggest that remodelling or degradation of one or more cell wall polysaccharides is important for plant immunity against B. cinerea and plays a role in pathogen-induced JA-Ile and camalexin accumulation. One-sentence summaryBXL4 is a putative bifunctional xylosidase/arabinofuranisodase localising to the apoplast, important for immunity against the necrotrphic pathogen B. cinerea.

plant biology↗

bioRxiv2019

From isochorismate to salicylate: a new reaction mechanism for salicylic acid biosynthesis

The phytohormone salicylic acid (SA) is a central regulator of plant immunity. Despite such functional importance, our knowledge of its biosynthesis is incomplete. Previous work showed that SA is synthesized from chorismic acid in plastids. The bulk of pathogen-induced SA derives from isochorismate generated by the catalytic activity of ISOCHORISMATE SYNTHASE1 (ICS1). How and in which cellular compartment isochorismate is converted to SA is unknown. Here we show that the pathway downstream of isochorismate requires only two additional proteins: the plastidial isochorismate exporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) and the cytosolic amido-transferase AvrPphB SUSCEPTIBLE3 (PBS3). PBS3 catalyzes the conjugation of glutamate to isochorismate. The reaction product isochorismate-9-glutamate spontaneously decomposes into enolpyruvyl-N-glutamate and SA. This previously unknown reaction mechanism appears to be conserved throughout the plant kingdom.\n\nOne Sentence SummarySalicylic acid is synthesized via isochorismate-9-glutamate by PBS3.

plant biology↗