White blister rust, caused by the oomycete Albugo candida, is a widespread disease of Brassica crops. The Arabidopsis CSA1/DAR4 (also known as CSA1/CHS3) paired immune receptor carries an Integrated Domain (ID) with homology to the DA1... more
White blister rust, caused by the oomycete Albugo candida, is a widespread disease of Brassica crops. The Arabidopsis CSA1/DAR4 (also known as CSA1/CHS3) paired immune receptor carries an Integrated Domain (ID) with homology to the DA1 family of peptidases. Using domain swaps with DA1 family members, we show that the DAR4 ID acts as an integrated decoy for DAR3, which interacts with and inhibits the peptidase activities of DA1, DAR1 and DAR2 family members. Albugo infection rapidly lowered DAR3 levels and activates DA1 peptidase activity. This promotes endoreduplication of host tissues to support pathogen growth. We propose that DAR4/CSA1 senses the actions of a putative Albugo effector that reduces DAR3 levels and initiates defense.
Research Interests: Biology and Arabidopsis
Plant disease resistance involves both detection of microbial molecular patterns by cell-surface pattern recognition receptors and detection of pathogen effectors by intracellular NLR immune receptors. NLRs are classified as sensor NLRs,... more
Plant disease resistance involves both detection of microbial molecular patterns by cell-surface pattern recognition receptors and detection of pathogen effectors by intracellular NLR immune receptors. NLRs are classified as sensor NLRs, involved in effector detection, or helper NLRs required for sensor NLR signalling. TIR-domain-containing sensor NLRs (TNLs) require helper NLRs NRG1 and ADR1 for resistance, and their activation of defense also requires the lipase-domain proteins EDS1, SAG101 and PAD4. We investigated how the helper NLR NRG1 supports TNL-initiated immunity with EDS1 and SAG101. We find that NRG1 associates with EDS1 and SAG101 at the plasma membrane and in the nucleus, but only self-associates at the plasma membrane. Activation of TNLs is sufficient to trigger NRG1-EDS1-SAG101 interaction, but cell-surface receptor-initiated defense is also required to form an oligomeric Resistosome. The data point to formation of NRG1-EDS1-SAG101 heterotrimers in the nucleus upon i...
Research Interests:
Research Interests:
Late blight caused by the oomycete pathogenPhytophthora infestanscontinues to cause major worldwide losses in potato and tomato. Most accessions ofSolanum americanum, a globally distributed, wild Solanaceae plant, are highly resistant to... more
Late blight caused by the oomycete pathogenPhytophthora infestanscontinues to cause major worldwide losses in potato and tomato. Most accessions ofSolanum americanum, a globally distributed, wild Solanaceae plant, are highly resistant to late blight. We generated high-quality reference genomes of fourS. americanumaccessions, re-sequenced 52 accessions, and we defined variation in the NLR immune receptor genes (theS. americanumNLRome). We further screened for variation in recognition of ∼315P. infestansRXLR effectors in 52S. americanumaccessions. Using these genotypic and phenotypic data, we cloned three novel NLR-encoding genesRpi-amr4, Rpi-amr16andRpi-amr17, and determined their corresponding RXLR effector genesAvramr4(PITG_22825),Avramr16(PITG_02860) andAvramr17(PITG_04373) fromP. infestans. These genomic resources and methodology will support efforts to convert potato into a “nonhost” of late blight and can be applied to diseases of other crops.
Research Interests:
Progeny of tobacco line 2853.6, which carries a streptomycin phosphotransferase (SPT) gene interrupted by the maize element Activator (Ac), were selected for streptomycin resistance (Spr) because of germinal Ac excision. Some events gave... more
Progeny of tobacco line 2853.6, which carries a streptomycin phosphotransferase (SPT) gene interrupted by the maize element Activator (Ac), were selected for streptomycin resistance (Spr) because of germinal Ac excision. Some events gave rise to Spr alleles that were unstable and exhibited a mottled phenotype on streptomycin-containing medium due to somatic loss of SPT function. This instability was most pronounced in one particular line, Spr12F. Other Spr alleles rarely exhibited silencing of SPT. Streptomycin-sensitive, homozygous Spr12F plants were recovered, and crosses were performed with other, more stable Spr lines. A high proportion of the resulting heterozygous progeny were silenced for SPT expression. The silenced state was heritable even after the Spr12F allele segregated away. No correlation could be made between silencing and methylation of the SPT gene. Structural analysis of allele Spr12F showed that the SPT gene from which Ac had excised was flanked by direct repeats...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Gram-negative phytopathogenic bacteria translocate effector proteins into plant cells to subvert host defenses. These effectors can be recognized by plant nucleotide-binding-leucine-rich repeat immune receptors, triggering defense... more
Gram-negative phytopathogenic bacteria translocate effector proteins into plant cells to subvert host defenses. These effectors can be recognized by plant nucleotide-binding-leucine-rich repeat immune receptors, triggering defense responses that restrict pathogen growth. AvrRps4, an effector protein from Pseudomonas syringae pv. pisi, triggers RPS4-dependent immunity in resistant accessions of Arabidopsis. To better understand the molecular basis of AvrRps4-triggered immunity, we determined the crystal structure of processed AvrRps4 (AvrRps4(C), residues 134-221), revealing that it forms an antiparallel α-helical coiled coil. Structure-informed mutagenesis reveals an electronegative surface patch in AvrRps4(C) required for recognition by RPS4; mutations in this region can also uncouple triggering of the hypersensitive response from disease resistance. This uncoupling may result from a lower level of defense activation, sufficient for avirulence but not for triggering a hypersensitiv...
Research Interests: Biology, Tobacco, Cell Biology, Confocal Microscopy, Medicine, and 15 moreMultidisciplinary, Plasmids, Arabidopsis, Pseudomonas Syringae, Analytical Ultracentrifugation, Genetic variation, Protein Conformation, Yeasts, Plant immunity, Hypersensitive Response, DNA binding proteins, Site-directed Mutagenesis, Innate Immune System, Immunoblotting, and Nicotiana benthamiana
Research Interests: Genetics, Plant Biology, Biology, Medicine, Gene expression, and 15 moreIn Situ Hybridization, Meiosis, Plant, Homology, Gene, Arabidopsis, Introns, Gen, Genetic variation, Amino Acid Sequence, Base Sequence, Cell Cycle Proteins, DNA binding proteins, Molecular Sequence Data, and Nucleotide sequence
SummaryGenome sequences of plant fungal pathogens have enabled the identification of effectors that cooperatively modulate the cellular environment for successful fungal growth and suppress host defense. Identification and... more
SummaryGenome sequences of plant fungal pathogens have enabled the identification of effectors that cooperatively modulate the cellular environment for successful fungal growth and suppress host defense. Identification and characterization of novel effector proteins are crucial for understanding pathogen virulence and host‐plant defense mechanisms. Previous reports indicate that the Pseudomonas syringae pv. tomato DC3000 type III secretion system (T3SS) can be used to study how non‐bacterial effectors manipulate dicot plant cell function using the effector detector vector (pEDV) system. Here we report a pEDV‐based effector delivery system in which the T3SS of Burkholderia glumae, an emerging rice pathogen, is used to translocate the AVR‐Pik and AVR‐Pii effectors of the fungal pathogen Magnaporthe oryzae to rice cytoplasm. The translocated AVR‐Pik and AVR‐Pii showed avirulence activity when tested in rice cultivars containing the cognate R genes. AVR‐Pik reduced and delayed the hyper...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Biology, Calcium, Cell Biology, Medicine, Signal Transduction, and 14 moreBiological Sciences, Mutation, Reactive Oxygen Species, Calcium channels, Stomata, Gene, Arabidopsis, Abscisic Acid, NADPH oxidase, Hydrogen Peroxide, Gene Function, Base Sequence, Medical and Health Sciences, and Protein subunits
Research Interests: Genetics, Biotechnology, Biology, Molecular Genetics, Medicine, and 15 moreMultidisciplinary, Genetic Engineering, Plant diseases, Disease resistance, Homology, Genetic transformation, Gene, Molecular cloning, Gen, Plant Disease, Plant Pathology, Amino Acid Sequence, Plant Disease Resistance, Molecular Sequence Data, and Nucleotide sequence
Plants have evolved a powerful immune system to defend against infection by most microbial organisms. However, successful pathogens, such as Pseudomonas syringae , have developed countermeasures and inject virulence proteins into the host... more
Plants have evolved a powerful immune system to defend against infection by most microbial organisms. However, successful pathogens, such as Pseudomonas syringae , have developed countermeasures and inject virulence proteins into the host plant cell to suppress immunity and cause devastating diseases. Despite intensive research efforts, the molecular targets of bacterial virulence proteins that are important for plant disease development have remained obscure. Here, we show that a conserved P. syringae virulence protein, HopM1, targets an immunity-associated protein, AtMIN7, in Arabidopsis thaliana . HopM1 mediates the destruction of AtMIN7 via the host proteasome. Our results illustrate a strategy by which a bacterial pathogen exploits the host proteasome to subvert host immunity and causes infection in plants.
Research Interests: Microbiology, Biology, Innate immunity, Medicine, Multidisciplinary, and 15 moreArabidopsis thaliana, Plant diseases, Mutation, Immunity, Pathogen, Arabidopsis, Glucans, Pseudomonas Syringae, Immune system, Plant Disease, Plant immunity, Host Plant, Protein Transport, Plant Leaves, and Innate Immune System
A major class of plant disease resistance ( R ) genes encodes leucine-rich-repeat proteins that possess a nucleotide binding site and amino-terminal similarity to the cytoplasmic domains of the Drosophila Toll and human IL-1 receptors. In... more
A major class of plant disease resistance ( R ) genes encodes leucine-rich-repeat proteins that possess a nucleotide binding site and amino-terminal similarity to the cytoplasmic domains of the Drosophila Toll and human IL-1 receptors. In Arabidopsis thaliana , EDS1 is indispensable for the function of these R genes. The EDS1 gene was cloned by targeted transposon tagging and found to encode a protein that has similarity in its amino-terminal portion to the catalytic site of eukaryotic lipases. Thus, hydrolase activity, possibly on a lipid-based substrate, is anticipated to be central to EDS1 function. The predicted EDS1 carboxyl terminus has no significant sequence homologies, although analysis of eight defective eds1 alleles reveals it to be essential for EDS1 function. Two plant defense pathways have been defined previously that depend on salicylic acid, a phenolic compound, or jasmonic acid, a lipid-derived molecule. We examined the expression of EDS1 mRNA and marker mRNAs ( PR1...
Research Interests: Biology, Medicine, Multidisciplinary, Arabidopsis thaliana, Humans, and 15 moreMutation, Disease resistance, Gene, Arabidopsis, PLANT DEFENSE, Phenolic compound, Eukaryotic Cells, Amino Acid Sequence, Base Sequence, Plant Disease Resistance, DNA binding proteins, Lipase, Jasmonic Acid, Molecular Sequence Data, and mRNA expression
Reactive oxygen intermediates (ROI) are strongly associated with plant defense responses. The origin of these ROI has been controversial. Arabidopsis respiratory burst oxidase homologues ( rboh genes) have been proposed to play a role in... more
Reactive oxygen intermediates (ROI) are strongly associated with plant defense responses. The origin of these ROI has been controversial. Arabidopsis respiratory burst oxidase homologues ( rboh genes) have been proposed to play a role in ROI generation. We analyzed lines carrying dSpm insertions in the highly expressed AtrbohD and AtrbohF genes. Both are required for full ROI production observed during incompatible interactions with the bacterial pathogen Pseudomonas syringae pv. tomato DC3000( avrRpm1 ) and the oomycete parasite Peronospora parasitica . We also observed reduced cell death, visualized by trypan blue stain and reduced electrolyte leakage, in the Atrboh mutants after DC3000( avrRpm1 ) inoculation. However, enhanced cell death is observed after infection of mutant lines with P. parasitica . Paradoxically, although atrbohD mutation eliminated the majority of total ROI production, atrbohF mutation exhibited the strongest effect on cell death.
Research Interests:
Late blight, caused by the notorious pathogen Phytophthora infestans, is a devastating disease of potato (Solanum tuberosum) and tomato (Solanum lycopersicum), and during the 1840s caused the Irish potato famine and over one million... more
Late blight, caused by the notorious pathogen Phytophthora infestans, is a devastating disease of potato (Solanum tuberosum) and tomato (Solanum lycopersicum), and during the 1840s caused the Irish potato famine and over one million fatalities. Currently, grown potato cultivars lack adequate blight tolerance. Earlier cultivars bred for resistance used disease resistance genes that confer immunity only to some strains of the pathogen harboring corresponding avirulence gene. Specific resistance gene-mediated immunity and chemical controls are rapidly overcome in the field when new pathogen races arise through mutation, recombination, or migration from elsewhere. A mitogen-activated protein kinase (MAPK) cascade plays a pivotal role in plant innate immunity. Here we show that the transgenic potato plants that carry a constitutively active form of MAPK kinase driven by a pathogen-inducible promoter of potato showed high resistance to early blight pathogen Alternaria solani as well as P....
Research Interests: Biology, Tobacco, Medicine, Biological Sciences, Plant Physiology, and 15 morePlant diseases, Sequence alignment, Pathogen, Terpenes, Phenotype, Phytophthora, Pseudomonas Syringae, Blight, Solanum, Phytophthora infestans, Solanum Tuberosum, Plant Disease Resistance, PLANT PROTEINS, Molecular Sequence Data, and R gene
Research Interests:
The tomato Cf-9 and Cf-9B genes both confer resistance to the leaf mold fungus Cladosporium fulvum but only Cf-9 confers seedling resistance and recognizes the avirulence (Avr) protein Avr9 produced by C. fulvum. Using domain swaps,... more
The tomato Cf-9 and Cf-9B genes both confer resistance to the leaf mold fungus Cladosporium fulvum but only Cf-9 confers seedling resistance and recognizes the avirulence (Avr) protein Avr9 produced by C. fulvum. Using domain swaps, leucine-rich repeats (LRR) 5 to 15 of Cf-9 were shown to be required for Cf-9-specific resistance to C. fulvum in tomato, and the entire N-terminus up to LRR15 of Cf-9B was shown to be required for Cf-9B-specific resistance. Finer domain swaps showed that nine amino-acid differences in LRR 13 to 15 provided sufficient Cf-9-specific residues in a Cf-9B context for recognition of Avr9 in Nicotiana tabacum or sufficient Cf-9B residues in a Cf-9 context for a novel necrotic response caused by the expression of Cf-9B in N. benthamiana. The responses conferred by LRR 13 to 15 were enhanced by addition of LRR 10 to 12, and either region of Cf-9B was found to cause necrosis in N. benthamiana when the other was replaced by Cf-9 sequence in a Cf-9B context. As a c...
Research Interests: Genetics, Microbiology, Plant Biology, Biology, Tobacco, and 14 moreMedicine, Plant diseases, Resistance, Disease resistance, Molecular Plant Microbe Interactions, Host Pathogen Interactions, Amino Acid Sequence, Hypersensitive Response, Plant Disease Resistance, PLANT PROTEINS, Lycopersicon esculentum, Cladosporium, Molecular Sequence Data, and Nicotiana benthamiana
Cf-9 confers resistance to tomato seedlings and mature plants against Cladosporium fulvum races expressing the Avr9 elicitor. It is the central member of a cluster of five paralogous genes in an introgressed segment of chromosome 1... more
Cf-9 confers resistance to tomato seedlings and mature plants against Cladosporium fulvum races expressing the Avr9 elicitor. It is the central member of a cluster of five paralogous genes in an introgressed segment of chromosome 1 derived from Lycopersicon pimpinellifolium. The other four genes have been named Hcr9-9A, Hcr9-9B, Hcr9-9D, and Hcr9-9E. Hcr9-9B, here designated Cf-9B, encodes weaker resistance than Cf-9, recognizes a different elicitor, and protects only mature plants from infection. The onset of Cf-9B-mediated resistance and the molecular basis for its developmental control were investigated in this study. Fungal inoculation of tomato plants containing reciprocal Cf-9/Cf-9B promoter-coding region swaps, analysis of tomato plants containing promoter-gusA fusions, and a reverse transcriptase-polymerase chain reaction study of Cf-9 and Cf-9B transcripts in tomato plants suggested that transcriptional control of Cf-9B did not account for the late onset of Cf-9B-mediated r...
Research Interests:
We present here the characterization of a new gene family, awr, found in all sequenced Ralstonia solanacearum strains and in other bacterial pathogens. We demonstrate that the five paralogues in strain GMI1000 encode type III-secreted... more
We present here the characterization of a new gene family, awr, found in all sequenced Ralstonia solanacearum strains and in other bacterial pathogens. We demonstrate that the five paralogues in strain GMI1000 encode type III-secreted effectors and that deletion of all awr genes severely impairs its capacity to multiply in natural host plants. Complementation studies show that the AWR (alanine-tryptophan-arginine tryad) effectors display some functional redundancy, although AWR2 is the major contributor to virulence. In contrast, the strain devoid of all awr genes (Δawr1-5) exhibits enhanced pathogenicity on Arabidopsis plants. A gain-of-function approach expressing AWR in Pseudomonas syringae pv. tomato DC3000 proves that this is likely due to effector recognition, because AWR5 and AWR4 restrict growth of this bacterium in Arabidopsis. Transient overexpression of AWR in nonhost tobacco species caused macroscopic cell death to varying extents, which, in the case of AWR5, shows chara...
Research Interests: Genetics, Microbiology, Genomics, Plant Biology, Biology, and 15 moreMedicine, Phylogeny, Plant diseases, Cell Death, Complementation, Plants, Gene, Molecular Plant Microbe Interactions, Arabidopsis, Host Pathogen Interactions, Gens, Pathogenic Bacteria, Pathogenic microorganisms, Plant Leaves, and Plantes
RPP5 is the seminal example of a cytoplasmic NB-LRR receptor-like protein that confers downy mildew resistance in Arabidopsis thaliana. In this study, we describe the cloning and molecular characterization of the gene encoding ATR5Emoy2,... more
RPP5 is the seminal example of a cytoplasmic NB-LRR receptor-like protein that confers downy mildew resistance in Arabidopsis thaliana. In this study, we describe the cloning and molecular characterization of the gene encoding ATR5Emoy2, an avirulence protein from the downy mildew pathogen Hyaloperonospora arabidopsidis isolate Emoy2. ATR5Emoy2 triggers defense response in host lines expressing the functional RPP5 allele from Landsberg erecta (Ler-0). ATR5Emoy2 is embedded in a cluster with two additional ATR5-like (ATR5L) genes, most likely resulting from gene duplications. ATR5L proteins do not trigger RPP5-mediated resistance and the copy number of ATR5L genes varies among H. arabidopsidis isolates. ATR5Emoy2 and ATR5L proteins contain a signal peptide, canonical EER motif, and an RGD motif. However, they lack the canonical translocation motif RXLR, which characterizes most oomycete effectors identified so far. The signal peptide and the N-terminal regions including the EER motif...
Research Interests: Genetics, Microbiology, Plant Biology, Biology, Plant Molecular Biology, and 15 moreMedicine, Plant diseases, Disease resistance, Gene, Gene Duplication, Molecular Plant Microbe Interactions, Arabidopsis, Oomycetes, Genes, Molecular cloning, Amino Acid Sequence, Base Sequence, Downy Mildew, Gene expression profiling, and Molecular Sequence Data
Research Interests: Chemistry, Biology, Calcium, Cell Biology, Biological Chemistry, and 15 moreMedicine, Biological Sciences, Protein Kinases, Mutation, Reactive Oxygen Species, Phosphorylation, NADPH oxidase, CHEMICAL SCIENCES, Palmitoylation, Plant immunity, PLANT PROTEINS, Lycopersicon esculentum, Cell Membrane, Myristoylation, and Medical and Health Sciences
Research Interests:
The interaction between tomato (Lycopersicon esculentum) and the leaf mold pathogen Cladosporium fulvum is an excellent model for investigating disease resistance gene evolution. The interaction is controlled in a gene-for-gene manner by... more
The interaction between tomato (Lycopersicon esculentum) and the leaf mold pathogen Cladosporium fulvum is an excellent model for investigating disease resistance gene evolution. The interaction is controlled in a gene-for-gene manner by Cf genes that encode type I transmembrane extracellular leucinerich repeat glycoproteins that recognize their cognate fungal avirulence (Avr) proteins. Cf-4 from L. hirsutum and Cf-9 from L. pimpinellifolium are located at the same locus on the short arm of tomato chromosome 1 in an array of five paralogs. Molecular analysis has shown that one mechanism for generating sequence variation in Cf genes is intragenic sequence exchange through unequal crossing over or gene conversion. To investigate this we used a facile genetic selection to identify novel haplotypes in the progeny of Cf-4/Cf-9 trans-heterozygotes that lacked Cf-4 and Cf-9. This selection is based on the ability of Avr4 and Avr9 to induce Cf-4- or Cf-9-dependent seedling death. The crosso...
Research Interests:
Research Interests: Biology, Oxidative Stress, Medicine, Biological Sciences, Antioxidants, and 15 morePlant diseases, Botrytis, Reactive Oxygen Species, Anthocyanins, Genotype, Food Storage, Botrytis cinerea, Postharvest, Ripening, PLANT PROTEINS, Anthocyanin, Malondialdehyde, Lycopersicon esculentum, Psychology and Cognitive Sciences, and Medical and Health Sciences
Research Interests:
Research Interests:
Research Interests:
Potato (Solanum tuberosum) and tomato (Solanum lycopersicon) crops suffer severe losses to late blight caused by the oomycete pathogen Phytophthora infestans. Solanum americanum, a relative of potato and tomato, is globally distributed... more
Potato (Solanum tuberosum) and tomato (Solanum lycopersicon) crops suffer severe losses to late blight caused by the oomycete pathogen Phytophthora infestans. Solanum americanum, a relative of potato and tomato, is globally distributed and most accessions are highly blight resistant. We generated high-quality reference genomes of four S. americanum accessions, resequenced 52 accessions, and defined a pan-NLRome of S. americanum immune receptor genes. We further screened for variation in recognition of 315P. infestans RXLR effectors in 52 S. americanum accessions. Using these genomic and phenotypic data, we cloned three NLR-encoding genes, Rpi-amr4, R02860 and R04373, that recognize cognate P. infestans RXLR effectors PITG_22825 (AVRamr4), PITG_02860 and PITG_04373. These genomic resources and methodologies will support efforts to engineer potatoes with durable late blight resistance and can be applied to diseases of other crops.
Research Interests:
Calcium-dependent protein kinases (CDPKs) comprise a large family of serine/threonine kinases in plants and protozoans. We isolated two related CDPK cDNAs (NtCDPK2 and NtCDPK3) from Nicotiana tabacum. These CDPK transcripts are elevated... more
Calcium-dependent protein kinases (CDPKs) comprise a large family of serine/threonine kinases in plants and protozoans. We isolated two related CDPK cDNAs (NtCDPK2 and NtCDPK3) from Nicotiana tabacum. These CDPK transcripts are elevated after race-specific defence elicitation and hypo-osmotic stress. Transiently expressed myc-epitope-tagged NtCDPK2 in Nicotiana benthamiana and N.tabacum leaves showed a rapid transient interconversion to an activated form after elicitation and hypo-osmotic stress. The Avr9 race-specific elicitor caused a more pronounced and sustained response. This transition is due to phosphorylation of the CDPK. Immuno complex kinase assays with epitope-tagged NtCDPK2 showed that stress-induced phosphorylation and interconversion of NtCDPK2 correlates with an increase in enzymatic activity. The function of NtCDPK2 in plant defence was investigated by employing virus-induced gene silencing (VIGS) in N.benthamiana. CDPK-silenced plants showed a reduced and delayed hy...
Research Interests: Biology, Cell Biology, Medicine, Gene Silencing, Biological Sciences, and 15 morePlant diseases, Osmotic pressure, Phosphorylation, Plant Defence, Phenotype, Kinase, Nicotiana Tabacum, Amino Acid Sequence, Elicitor, Calcium Binding Proteins, Hypersensitive Response, Enzyme Induction, Molecular Sequence Data, Nicotiana benthamiana, and Medical and Health Sciences
Research Interests:
Research Interests:
Recent advances in DNA sequencing techniques resulted in more than forty sequenced plant genomes representing a diverse set of taxa of agricultural, energy, medicinal and ecological importance. However, gene family curation is often only... more
Recent advances in DNA sequencing techniques resulted in more than forty sequenced plant genomes representing a diverse set of taxa of agricultural, energy, medicinal and ecological importance. However, gene family curation is often only inferred from DNA sequence homology and lacks insights into evolutionary processes contributing to gene family dynamics. In a comparative genomics framework, we integrated multiple lines of evidence provided by gene synteny, sequence homology and protein-based Hidden Markov Modelling to extract homologous super-clusters composed of multi-domain resistance (R)-proteins of the NB-LRR type (for NUCLEOTIDE BINDING/LEUCINE-RICH REPEATS), that are involved in plant innate immunity. To assess the diversity of R-proteins within and between species, we screened twelve eudicot plant genomes including six major crops and found a total of 2,363 NB-LRR genes. Our curated R-proteins set shows a 50% average for tandem duplicates and a 22% fraction of gene copies r...
Research Interests: Genetics, Genomics, Computational Biology, Molecular Evolution, Comparative Genomics, and 15 moreBiology, Medicine, Biological Sciences, Plant Genome Project, Disease resistance, Cluster Analysis, Plants, Genome, Gene, Gene Duplication, Gene Family, PLANT PROTEINS, Synteny, conserved sequence , and Medical and Health Sciences
We previously identified three Avr9/Cf-9 Rapidly Elicited (ACRE) genes essential for Cf-9– and Cf-4–dependent hypersensitive response (HR) production in Nicotiana benthamiana. Two of them encode putative E3 ubiquitin ligase components.... more
We previously identified three Avr9/Cf-9 Rapidly Elicited (ACRE) genes essential for Cf-9– and Cf-4–dependent hypersensitive response (HR) production in Nicotiana benthamiana. Two of them encode putative E3 ubiquitin ligase components. This led us to investigate other ACRE genes associated with the ubiquitination pathway. ACRE74 encodes a U-box E3 ligase homolog, highly related to parsley (Petroselinum crispum) CMPG1 and Arabidopsis thaliana PLANT U-BOX20 (PUB20) and PUB21 proteins, and was called Nt CMPG1. Transcript levels of Nt CMPG1 and the homologous tomato (Solanum lycopersicum) Cmpg1 are induced in Cf9 tobacco (Nicotiana tabacum) and Cf9 tomato after Avr9 elicitation. Tobacco CMPG1 possesses in vitro E3 ligase activity. N. benthamiana plants silenced for Nt CMPG1 show reduced HR after Cf-9/Avr9 elicitation, while overexpression of Nt CMPG1 induces a stronger HR in Cf9 tobacco plants after Avr9 infiltration. In tomato, silencing of Cmpg1 decreased resistance to Cladosporium fu...
Research Interests: Genetics, Plant Biology, Biology, Tobacco, Innate immunity, and 15 moreMedicine, Arabidopsis thaliana, Plant diseases, Sequence alignment, Mutation, Gene, Nicotiana Tabacum, Amino Acid Sequence, Base Sequence, Hypersensitive Response, PLANT PROTEINS, Lycopersicon esculentum, Biochemistry and cell biology, Molecular Sequence Data, and Nicotiana benthamiana
Research Interests: Microbiology, Biology, Innate immunity, Medicine, Gene Silencing, and 15 moreBiological Sciences, Phylogeny, Cell Death, Gene, Plant Defence, Hydrogen Peroxide, Amino Acid Sequence, Base Sequence, Hypersensitive Response, Plant Disease Resistance, Oxidants, Lycopersicon esculentum, Molecular Sequence Data, Nicotiana benthamiana, and Medical and Health Sciences
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Tomato (Lycopersicon esculentum) Cf genes confer resistance to the fungal pathogen Cladosporium fulvum through recognition of secreted avirulence (Avr) peptides. Plant defense responses, including rapid alterations in gene expression, are... more
Tomato (Lycopersicon esculentum) Cf genes confer resistance to the fungal pathogen Cladosporium fulvum through recognition of secreted avirulence (Avr) peptides. Plant defense responses, including rapid alterations in gene expression, are immediately activated upon perception of the pathogen. Previously, we identified a collection of Avr9/Cf-9 rapidly (15 to 30 min) elicited (ACRE) genes from tobacco (Nicotiana tabacum). Many of the ACRE genes encode putative signaling components and thus may play pivotal roles in the initial development of the defense response. To assess the requirement of 42 of these genes in the hypersensitive response (HR) induced by Cf-9/Avr9 or by Cf-4/Avr4, we used virus-induced gene silencing (VIGS) in N. benthamiana. Three genes were identified that when silenced compromised the Cf-mediated HR. We further characterized one of these genes, which encodes a Ser/Thr protein kinase called Avr9/Cf-9 induced kinase 1 (ACIK1). ACIK1 mRNA was rapidly upregulated in ...
Research Interests: Genetics, Functional Analysis, Plant Biology, Biology, Tobacco, and 13 moreInnate immunity, Gene Silencing, Plant diseases, Disease resistance, Tomato, Plant viruses, Time Factors, Plant cell, Protein Kinase, PLANT PROTEINS, Lycopersicon esculentum, Biochemistry and cell biology, and Molecular Sequence Data
Research Interests:
Research Interests:
Research Interests: Biology, Fluorescent Dyes and Reagents, Cryopreservation, Biological Sciences, DNA, and 15 moreComputers, Animals, Male, Polymerase Chain Reaction, Genetic variation, Acrosome, Spermatozoa, Semen Preservation, Cell Survival, Genetic Markers, Organic Chemicals, Biology Reproduction, Cell Membrane, fluorescent dyes, and Medical and Health Sciences
Plants use intracellular immune receptors (NLRs) to detect pathogen-derived effector proteins. The Arabidopsis NLR pair RRS1-R/RPS4 confers disease resistance to different bacterial pathogens by perceiving structurally distinct effectors... more
Plants use intracellular immune receptors (NLRs) to detect pathogen-derived effector proteins. The Arabidopsis NLR pair RRS1-R/RPS4 confers disease resistance to different bacterial pathogens by perceiving structurally distinct effectors AvrRps4 from Pseudomonas syringae pv. pisi and PopP2 from Ralstonia solanacearum via an integrated WRKY domain in RRS1-R. How the WRKY domain of RRS1 (RRS1WRKY) perceives distinct classes of effector to initiate an immune response is unknown. We report here the crystal structure of the in planta processed C-terminal domain of AvrRps4 (AvrRps4C) in complex with RRS1WRKY. Perception of AvrRps4C by RRS1WRKY is mediated by the β2-β3 segment of RRS1WRKY that binds an electronegative patch on the surface of AvrRps4C. Structure-based mutations that disrupt AvrRps4C/RRS1WRKY interactions in vitro compromise RRS1/RPS4-dependent immune responses. We also show that AvrRps4C can associate with the WRKY domain of the related but distinct RRS1B/RPS4B NLR pair, an...
Research Interests:
SummaryThe oomycete Albugo candida causes white blister rust, an important disease of Brassica crops. Distinct races of A. candida are defined by their specificity for infecting different host species.The White Rust Resistance 4 (WRR4)... more
SummaryThe oomycete Albugo candida causes white blister rust, an important disease of Brassica crops. Distinct races of A. candida are defined by their specificity for infecting different host species.The White Rust Resistance 4 (WRR4) locus in Col-0 accession of Arabidopsis thaliana contains three genes that encode TIR-NLR resistance proteins. The Col-0 alleles of WRR4A and WRR4B confer resistance to at least four A. candida races (2, 7 and 9 from B. juncea, B. rapa and B. oleracea, respectively, and Race 4 from Capsella bursa-pastoris). Resistance mediated by both paralogs can be overcome by Col-0-virulent isolates of Race 4.After comparing repertoires of candidate effectors in resisted and resistance-breaking strains, we used transient co-expression in tobacco or Arabidopsis to identify effectors recognized by WRR4A and WRR4B. A library of CCG effectors from four A. candida races was screened for WRR4A- or WRR4B- dependent elicitation of hypersensitive response (HR). These CCG ge...
Research Interests: Biology and Arabidopsis
Albugo candida is an obligate oomycete pathogen that infects many plants in the Brassicaceae family. We re-sequenced the genome of isolate Ac2V using PacBio long reads and constructed an assembly augmented by Illumina reads. The Ac2VPB... more
Albugo candida is an obligate oomycete pathogen that infects many plants in the Brassicaceae family. We re-sequenced the genome of isolate Ac2V using PacBio long reads and constructed an assembly augmented by Illumina reads. The Ac2VPB genome assembly is 10% larger and more contiguous compared to a previous version. Our annotation of the new assembly, aided by RNASeq information, revealed a dramatic 250% expansion (40 to 110) in the CHxC effector class, which we redefined as “CCG” based on motif analysis. This class of effectors consist of arrays of phylogenetically related paralogs residing in gene sparse regions, and shows signatures of positive selection and presence/absence polymorphism. This work provides a resource that allows the dissection of the genomic components underlying A. candida adaptation and particularly the role of CCG effectors in virulence and avirulence on different hosts.