ORCID Profile
0000-0003-0192-9041
Current Organisations
The University of Auckland
,
The New Zealand Institute for Plant & Food Research Limited
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Publisher: Public Library of Science (PLoS)
Date: 27-05-2022
DOI: 10.1371/JOURNAL.PPAT.1010542
Abstract: A pandemic isolate of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) has devastated kiwifruit orchards growing cultivars of Actinidia chinensis . In contrast, A . arguta (kiwiberry) is not a host of Psa3. Resistance is mediated via effector-triggered immunity, as demonstrated by induction of the hypersensitive response in infected A . arguta leaves, observed by microscopy and quantified by ion-leakage assays. Isolates of Psa3 that cause disease in A . arguta have been isolated and analyzed, revealing a 51 kb deletion in the exchangeable effector locus (EEL). This natural EEL-mutant isolate and strains with synthetic knockouts of the EEL were more virulent in A . arguta plantlets than wild-type Psa3. Screening of a complete library of Psa3 effector knockout strains identified increased growth in planta for knockouts of four effectors–AvrRpm1a, HopF1c, HopZ5a, and the EEL effector HopAW1a –suggesting a resistance response in A . arguta . Hypersensitive response (HR) assays indicate that three of these effectors trigger a host species-specific HR. A Psa3 strain with all four effectors knocked out escaped host recognition, but a cumulative increase in bacterial pathogenicity and virulence was not observed. These avirulence effectors can be used in turn to identify the first cognate resistance genes in Actinidia for breeding durable resistance into future kiwifruit cultivars.
Publisher: Wiley
Date: 08-2022
Abstract: Bacterial pathogens are major causes of crop diseases, leading to significant production losses. For instance, kiwifruit canker, caused by the phytopathogen Pseudomonas syringae pv. actinidiae ( Psa ), has posed a global challenge to kiwifruit production. Treatment with copper and antibiotics, whilst initially effective, is leading to the rise of bacterial resistance, requiring new biocontrol approaches. Previously, we isolated a group of closely related Psa phages with biocontrol potential, which represent environmentally sustainable antimicrobials. However, their deployment as antimicrobials requires further insight into their properties and infection strategy. Here, we provide an in‐depth examination of the genome of ΦPsa374‐like phages and show that they use lipopolysaccharides (LPS) as their main receptor. Through proteomics and cryo‐electron microscopy of ΦPsa374, we revealed the structural proteome and that this phage possess a T = 9 capsid triangulation, unusual for myoviruses. Furthermore, we show that ΦPsa374 phage resistance arises in planta through mutations in a glycosyltransferase involved in LPS synthesis. Lastly, through in vitro evolution experiments we showed that phage resistance is overcome by mutations in a tail fibre and structural protein of unknown function in ΦPsa374. This study provides new insight into the properties of ΦPsa374‐like phages that informs their use as antimicrobials against Psa .
Publisher: Springer Science and Business Media LLC
Date: 15-06-2017
DOI: 10.1038/S41598-017-03704-X
Abstract: Type-III secreted effectors (T3Es) play critical roles during bacterial pathogenesis in plants. Plant recognition of certain T3Es can trigger defence, often accompanied by macroscopic cell death, termed the hypersensitive response (HR). Economically important species of kiwifruit are susceptible to Pseudomonas syringae pv. actinidiae ( Psa ), the causal agent of kiwifruit bacterial canker. Although Psa is non-pathogenic in Arabidopsis thaliana , we observed that a T3E, HopZ5 that is unique to a global outbreak clade of Psa , triggers HR and defence in Arabidopsis accession Ct-1. Ws-2 and Col-0 accessions are unable to produce an HR in response to Pseudomonas -delivered HopZ5. While Ws-2 is susceptible to virulent bacterial strain Pseudomonas syringae pv. tomato DC3000 carrying HopZ5, Col-0 is resistant despite the lack of an HR. We show that HopZ5, like other members of the YopJ superfamily of acetyltransferases that it belongs to, autoacetylates lysine residues. Through comparisons to other family members, we identified an acetyltransferase catalytic activity and demonstrate its requirement for triggering defence in Arabidopsis and Nicotiana species. Collectively, data herein indicate that HopZ5 is a plasma membrane-localized acetyltransferase with autoacetylation activity required for avirulence.
Publisher: Scientific Societies
Date: 13-10-2023
DOI: 10.1094/PHYTOFR-04-23-0054-A
Abstract: The genome of Pseudomonas syringae pv. actinidifoliorum ICMP18803 (Pfm) was sequenced using the Oxford Nanopore minION platform to an average read depth of 123 fold. The genome assembled into a single chromosome of 6,353,853 bp after error-correction with Illumina short reads using Pilon. No plasmids were detected. Despite Pfm only being a relatively weak pathogen of kiwifruit, a set of 31 effectors, 26 of which were full length, was identified by mapping the comprehensive effector library generated by Dillon et al. (2019) to the assembled chromosome. A revised Pfm genome with the effector complement correctly named and annotated was resubmitted to Genbank (CP081457).
Publisher: Scientific Societies
Date: 07-2018
DOI: 10.1094/PHYTO-07-17-0233-R
Abstract: Venturia effusa (syn. Fusicladium effusum), causal agent of pecan scab, is the most prevalent pathogen of pecan (Carya illinoinensis), causing severe yield losses in the southeastern United States. V. effusa is currently known only by its asexual (conidial) stage. However, the degree and distribution of genetic ersity observed within and among populations of V. effusa are typical of a sexually reproducing fungal pathogen, and comparable with other dothideomycetes with a known sexual stage, including the closely related apple scab pathogen, V. inaequalis. Using the mating type (MAT) idiomorphs from V. inaequalis, we identified a single MAT gene, MAT1-1-1, in a draft genome of V. effusa. The MAT1-1-1 locus is flanked by two conserved genes encoding a DNA lyase (APN2) and a hypothetical protein. The MAT locus spanning the flanking genes was lified and sequenced from a subset of 14 isolates, of which 7 contained MAT1-1-1 and the remaining s les contained MAT1-2-1. A multiplex polymerase chain reaction screen was developed to lify MAT1-1-1, MAT1-2-1, and a conserved reference gene encoding β-tubulin, and used to screen 784 monoconidial isolates of V. effusa collected from 11 populations of pecan across the southeastern United States. A hierarchical s ling protocol representing region, orchard, and tree allowed for analysis of MAT structure at different spatial scales. Analysis of this collection revealed the frequency of the MAT idiomorphs is in a 1:1 equilibrium of MAT1-1:MAT1-2. The apparent equilibrium of the MAT idiomorphs provides impetus for a renewed effort to search for the sexual stage of V. effusa. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Publisher: Cold Spring Harbor Laboratory
Date: 13-11-2022
DOI: 10.1101/2022.11.12.516272
Abstract: Testing effector-knockout strains of the Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) for reduced in planta growth in their native kiwifruit host revealed a number of non- redundant effectors that contribute to Psa3 pathogenicity. Conversely, complementation in the weak kiwifruit pathogen P. syringae pv. actinidifoliorum (Pfm) for increased growth identified redundant Psa3 effectors. Psa3 effectors hopAZ1a and HopS2b and the entire exchangeable effector locus ( ΔEEL 10 effectors) were significant contributors to bacterial colonisation of the host and were additive in their effects on pathogenicity. Four of the EEL effectors (HopD1a, AvrB2b, HopAW1a, and HopD2a) redundantly contribute to pathogenicity through suppression of pattern-triggered immunity (PTI). Important Psa3 effectors include several redundantly required effectors early in the infection process (HopZ5a, HopH1a, AvrPto1b, AvrRpm1a, and HopF1e). These largely target the plant immunity hub, RIN4. This comprehensive effector profiling revealed that Psa3 carries robust effector redundancy for a large portion of its effectors, covering a few functions critical to disease.
Publisher: Wiley
Date: 20-03-2023
DOI: 10.1111/NPH.18848
Abstract: Testing effector knockout strains of the Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) for reduced in planta growth in their native kiwifruit host revealed a number of nonredundant effectors that contribute to Psa3 virulence. Conversely, complementation in the weak kiwifruit pathogen P. syringae pv. actinidifoliorum (Pfm) for increased growth identified redundant Psa3 effectors. Psa3 effectors hopAZ1a and HopS2b and the entire exchangeable effector locus ( ΔEEL 10 effectors) were significant contributors to bacterial colonisation of the host and were additive in their effects on virulence. Four of the EEL effectors (HopD1a, AvrB2b, HopAW1a and HopD2a) redundantly contribute to virulence through suppression of pattern‐triggered immunity (PTI). Important Psa3 effectors include several redundantly required effectors early in the infection process (HopZ5a, HopH1a, AvrPto1b, AvrRpm1a and HopF1e). These largely target the plant immunity hub, RIN4. This comprehensive effector profiling revealed that Psa3 carries robust effector redundancy for a large portion of its effectors, covering a few functions critical to disease.
Publisher: American Society for Microbiology
Date: 29-10-2015
Abstract: Pseudomonas syringae pv. actinidiae is the causal agent of bacterial canker of kiwifruit, a disease that has rapidly spread worldwide. We have fully sequenced and assembled the chromosomal and plasmid DNA from P. syringae pv. actinidiae ICMP 18884 using the PacBio RS II platform.
Publisher: Wiley
Date: 07-10-2020
Publisher: Public Library of Science (PLoS)
Date: 03-2017
Publisher: Wiley
Date: 23-09-2020
DOI: 10.1111/MPP.12989
Publisher: Cold Spring Harbor Laboratory
Date: 04-2020
DOI: 10.1101/2020.03.31.019141
Abstract: The common polysaccharide antigen (CPA) from the lipopolysaccharide (LPS) component of cell walls from the species complex Pseudomonas syringae is highly variable both in structure and immunological specificity, but the genetic basis for this is not well understood. We have characterised the CPA locus from P. syringae pv. actinidiae ( Psa ). This locus has a modular structure with genes for both L- and D- rhamnose (Rha) biosynthesis and that of an unknown sugar. It also contains an operon coding for ABC transporter subunits, a bifunctional glycosyltransferase and an O-methyltransferase. This operon is predicted to have a role in t ransport, e longation and t ermination of the Rha backbone of the CPA oligosaccharide and is referred to as the TET operon. This is the first report of the identification of this operon in P. syringae . Two alleles of the TET operon were present amongst the different biovars of Psa and lineages of the closely related pathovar P. syringae pv. actinidifoliorum . This allelic variation was reflected in the electrophoretic properties of purified LPS from the different isolates. Gene knockout of the TET operon allele from biovar 1 and replacement with that from biovar 3, demonstrated the link between the genetic locus and the electrophoretic and immunogenic properties of the LPS molecules in Psa . Sequence analysis of the TET operon from a wide range of P. syringae and P. viridiflava isolates displayed a phylogenetic history which is incongruent with core gene phylogeny, but correlates with previously reported tailocin sensitivity, suggesting a functional relationship between LPS structure and tailocin susceptibility.
Publisher: Cold Spring Harbor Laboratory
Date: 06-10-2022
DOI: 10.1101/2022.10.03.510724
Abstract: The complete genome of Pseudomonas syringae pv. actinidifoliorum ICMP18803 (Pfm) was sequenced using the Oxford Nanopore minION platform to an average read depth of 123. The genome assembled into a single chromosome of 6,353,853 bp after error-correction with Illumina short reads using Pilon. The complement of effector genes from a P. syringae pathovar plays the predominant role in defining its pathogenicity. Automatic gene annotation pipelines often poorly identify and name effector genes, however. Despite Pfm being a relatively weak pathogen of kiwifruit, a set of 31 effectors, 26 of which were full length, was identified by mapping the comprehensive effector library generated by Dillon et al. (2019). The Pfm genome with the effector complement, correctly named and annotated was resubmitted to Genbank ( CP081457 ).
Publisher: Cold Spring Harbor Laboratory
Date: 15-11-2021
DOI: 10.1101/2021.11.15.468702
Abstract: A pandemic isolate of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) has devastated kiwifruit orchards growing cultivars of Actinidia chinensis . In contrast, A. arguta (kiwiberry) is resistant to Psa3. This resistance is mediated via effector-triggered immunity, as demonstrated by induction of the hypersensitive response in infected A. arguta leaves, observed by microscopy and quantified by ion-leakage assays. Isolates of Psa3 that cause disease in A. arguta have been isolated and analyzed, revealing a 49 kb deletion in the exchangeable effector locus (EEL). This natural EEL-mutant isolate and strains with synthetic knockouts of the EEL were more virulent in A. arguta plantlets than wild-type Psa3. Screening of a complete library of Psa3 effector knockout strains identified increased growth in planta for knockouts of four effectors – AvrRpm1a, HopF1c, HopZ5a, and the EEL effector HopAW1a – suggesting a resistance response in A. arguta . Hypersensitive response (HR) assays indicate that three of these effectors trigger a host species-specific HR. A Psa3 strain with all four effectors knocked out escaped host recognition, but a cumulative increase in bacterial pathogenicity and virulence was not observed. These avirulence effectors can be used in turn to identify the first cognate resistance genes in Actinidia for breeding durable resistance into future kiwifruit cultivars.
Publisher: Scientific Societies
Date: 08-2021
DOI: 10.1094/MPMI-02-21-0043-R
Abstract: The infection of Pseudomonas syringae pv. actinidiae in kiwifruit is currently assessed by numerous methodologies, each with their own limitations. Most studies are based on either a laborious method of growth quantification of the pathogen or qualitative assessments by visual scoring following stem or cutting inoculation. Additionally, when assessing for resistance against specific pathogen effectors, confounding interactions between multiple genes in the pathogen can make mapping resistance phenotypes nearly impossible. Here, we present robust alternative methods to quantify pathogen load based on rapid bacterial DNA quantification by PCR, the use of Pseudomonas fluorescens, and a transient reporter eclipse assay for assessing resistance conferred by isolated bacterial avirulence genes. These assays compare well with bacterial plate counts to assess bacterial colonization as a result of plant resistance activation. The DNA-based quantification, when coupled with the P. fluorescens and reporter eclipse assays to independently identify bacterial avirulence genes, is rapid, highly reproducible, and scalable for high-throughput screens of multiple cultivars or genotypes. Application of these methodologies will allow rapid and high-throughput identification of resistant cultivars and the bacterial avirulence genes they recognize, facilitating resistance gene discovery for plant breeding programs. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Location: New Zealand
No related grants have been discovered for Matthew Templeton.