Publications by authors named "Paul R J Birch"

96 Publications

Haustorium formation and a distinct biotrophic transcriptome characterize infection of Nicotiana benthamiana by the tree pathogen Phytophthora kernoviae.

Mol Plant Pathol 2021 May 20. Epub 2021 May 20.

Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee, UK.

Phytophthora species cause some of the most serious diseases of trees and threaten forests in many parts of the world. Despite the generation of genome sequence assemblies for over 10 tree-pathogenic Phytophthora species and improved detection methods, there are many gaps in our knowledge of how these pathogens interact with their hosts. To facilitate cell biology studies of the infection cycle we examined whether the tree pathogen Phytophthora kernoviae could infect the model plant Nicotiana benthamiana. We transformed P. kernoviae to express green fluorescent protein (GFP) and demonstrated that it forms haustoria within infected N. benthamiana cells. Haustoria were also formed in infected cells of natural hosts, Rhododendron ponticum and European beech (Fagus sylvatica). We analysed the transcriptome of P. kernoviae in cultured mycelia, spores, and during infection of N. benthamiana, and detected 12,559 transcripts. Of these, 1,052 were predicted to encode secreted proteins, some of which may function as effectors to facilitate disease development. From these, we identified 87 expressed candidate RXLR (Arg-any amino acid-Leu-Arg) effectors. We transiently expressed 12 of these as GFP fusions in N. benthamiana leaves and demonstrated that nine significantly enhanced P. kernoviae disease progression and diversely localized to the cytoplasm, nucleus, nucleolus, and plasma membrane. Our results show that N. benthamiana can be used as a model host plant for studying this tree pathogen, and that the interaction likely involves suppression of host immune responses by RXLR effectors. These results establish a platform to expand the understanding of Phytophthora tree diseases.
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http://dx.doi.org/10.1111/mpp.13072DOI Listing
May 2021

All Roads Lead to Susceptibility: The Many Modes of Action of Fungal and Oomycete Intracellular Effectors.

Plant Commun 2020 Jul 24;1(4):100050. Epub 2020 Apr 24.

Division of Plant Sciences, School of Life Sciences, University of Dundee (at JHI), Invergowrie, Dundee DD2 5DA, UK.

The ability to secrete effector proteins that can enter plant cells and manipulate host processes is a key determinant of what makes a successful plant pathogen. Here, we review intracellular effectors from filamentous (fungal and oomycete) phytopathogens and the host proteins and processes that are targeted to promote disease. We cover contrasting virulence strategies and effector modes of action. Filamentous pathogen effectors alter the fates of host proteins that they target, changing their stability, their activity, their location, and the protein partners with which they interact. Some effectors inhibit target activity, whereas others enhance or utilize it, and some target multiple host proteins. We discuss the emerging topic of effectors that target negative regulators of immunity or other plant proteins with activities that support susceptibility. We also highlight the commonly targeted host proteins that are manipulated by effectors from multiple pathogens, including those representing different kingdoms of life.
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http://dx.doi.org/10.1016/j.xplc.2020.100050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7748000PMC
July 2020

The Ubiquitin E3 Ligase PUB17 Positively Regulates Immunity by Targeting a Negative Regulator, KH17, for Degradation.

Plant Commun 2020 Jul 13;1(4):100020. Epub 2020 Jul 13.

Division of Plant Science, School of Life Science, University of Dundee (at JHI), Invergowrie, Dundee DD2 5DA, UK.

Ubiquitination is a post-translational modification that regulates many processes in plants. Several ubiquitin E3 ligases act as either positive or negative regulators of immunity by promoting the degradation of different substrates. StPUB17 is an E3 ligase that has previously been shown to positively regulate immunity to bacteria, fungi and oomycetes, including the late blight pathogen . Silencing of promotes pathogen colonization and attenuates Cf4/avr4 cell death. Using yeast-2-hybrid and co-immunoprecipitation we identified the putative K-homology (KH) RNA-binding protein (RBP), StKH17, as a candidate substrate for degradation by StPUB17. StKH17 acts as a negative regulator of immunity that promotes infection and suppresses specific immune pathways. A KH RBP domain mutant of StKH17 (StKH17) is no longer able to negatively regulate immunity, indicating that RNA binding is likely required for StKH17 function. As StPUB17 is a known target of the ubiquitin E3 ligase, StPOB1, we reveal an additional step in an E3 ligase regulatory cascade that controls plant defense.
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http://dx.doi.org/10.1016/j.xplc.2020.100020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7371183PMC
July 2020

Devastating intimacy: the cell biology of plant-Phytophthora interactions.

New Phytol 2020 10 19;228(2):445-458. Epub 2020 Jun 19.

Cell and Molecular Sciences, James Hutton Institute, Errol Road, Invergowrie, Dundee, DD2 5DA, UK.

An understanding of the cell biology underlying the burgeoning molecular genetic and genomic knowledge of oomycete pathogenicity is essential to gain the full context of how these pathogens cause disease on plants. An intense research focus on secreted Phytophthora effector proteins, especially those containing a conserved N-terminal RXLR motif, has meant that most cell biological studies into Phytophthora diseases have focussed on the effectors and their host target proteins. While these effector studies have provided novel insights into effector secretion and host defence mechanisms, there remain many unanswered questions about fundamental processes involved in spore biology, host penetration and haustorium formation and function.
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http://dx.doi.org/10.1111/nph.16650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540312PMC
October 2020

RXLR Effectors Target Parallel Steps in an Immune Signal Transduction Pathway.

Plant Physiol 2019 08 19;180(4):2227-2239. Epub 2019 Jun 19.

Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University (HZAU), Wuhan 430070, People's Republic of China

The potato () blight pathogen delivers Arg-X-Leu-Arg (RXLR) effector proteins into host cells to subvert plant immune responses and promote colonization. We show that transient expression and stable transgenic expression of the RXLR effector Pi22926 in promotes leaf colonization by Pi22926 suppresses cell death triggered by coexpression of the avirulence protein Avr4 and the tomato () resistance protein Cf4. Pi22926 interacts with a potato mitogen-activated protein kinase kinase kinase, StMAP3Kβ2, in the nucleoplasm. Virus-induced gene silencing (VIGS) of the ortholog in enhances colonization and attenuates Cf4/Avr4-induced cell death, indicating that this host protein is a positive regulator of immunity. Cell death induced by Cf4/Avr4 is dependent on NbMAP3Kε and NbMAP3Kβ2, indicating that these MAP3Ks function in the same signaling pathway. VIGS of does not compromise cell death triggered by overexpression of MAP3Kε. Similarly, VIGS of does not attenuate cell death triggered by MAP3Kβ2, demonstrating that these MAP3K proteins function in parallel. In agreement, Pi22926 or another RXLR effector, PexRD2, only suppresses cell death triggered by expression of StMAP3Kβ2 or StMAP3Kε, respectively. Our data reveal that two effectors, PexRD2 and Pi22926, promote colonization by targeting MAP3K proteins that act in parallel in the same signal transduction pathway.
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http://dx.doi.org/10.1104/pp.18.00625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6670088PMC
August 2019

AVR2 Targets BSL Family Members, Which Act as Susceptibility Factors to Suppress Host Immunity.

Plant Physiol 2019 05 19;180(1):571-581. Epub 2019 Feb 19.

Division of Plant Science, School of Life Science, University of Dundee (at JHI), Invergowrie, Dundee DD2 5DA, United Kingdom

To be successful plant pathogens, microbes use "effector proteins" to manipulate host functions to their benefit. Identifying host targets of effector proteins and characterizing their role in the infection process allow us to better understand plant-pathogen interactions and the plant immune system. Yeast two-hybrid analysis and coimmunoprecipitation were used to demonstrate that the effector AVIRULENCE 2 (PiAVR2) interacts with all three BRI1-SUPPRESSOR1-like (BSL) family members from potato (). Transient expression of BSL1, BSL2, and BSL3 enhanced leaf infection. BSL1 and BSL3 suppressed INFESTIN 1 elicitin-triggered cell death, showing that they negatively regulate immunity. Virus-induced gene silencing studies revealed that BSL2 and BSL3 are required for BSL1 stability and show that basal levels of immunity are increased in -silenced plants. Immune suppression by BSL family members is dependent on the brassinosteroid-responsive host transcription factor CIB1/HBI1-like 1. The effector PiAVR2 targets all three BSL family members in the crop plant These phosphatases, known for their role in growth-promoting brassinosteroid signaling, all support virulence and thus can be regarded as susceptibility factors in late blight infection.
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http://dx.doi.org/10.1104/pp.18.01143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6501069PMC
May 2019

Phytophthora infestans effector SFI3 targets potato UBK to suppress early immune transcriptional responses.

New Phytol 2019 04 19;222(1):438-454. Epub 2019 Jan 19.

Division of Plant Science, School of Life Science, University of Dundee (at JHI), Invergowrie, Dundee, DD2 5DA, UK.

The potato blight agent Phytophthora infestans secretes a range of RXLR effectors to promote disease. Recent evidence indicates that some effectors suppress early pattern-triggered immunity (PTI) following perception of microbe-associated molecular patterns (MAMPs). Phytophthora infestans effector PiSFI3/Pi06087/PexRD16 has been previously shown to suppress MAMP-triggered pFRK1-Luciferase reporter gene activity. How PiSFI3 suppresses immunity is unknown. We employed yeast-two-hybrid (Y2H) assays, co-immunoprecipitation, transcriptional silencing by RNA interference and virus-induced gene silencing (VIGS), and X-ray crystallography for structure-guided mutagenesis, to investigate the function of PiSFI3 in targeting a plant U-box-kinase protein (StUBK) to suppress immunity. We discovered that PiSFI3 is active in the host nucleus and interacts in yeast and in planta with StUBK. UBK is a positive regulator of specific PTI pathways in both potato and Nicotiana benthamiana. Importantly, it contributes to early transcriptional responses that are suppressed by PiSFI3. PiSFI3 forms an unusual trans-homodimer. Mutation to disrupt dimerization prevents nucleolar localisation of PiSFI3 and attenuates both its interaction with StUBK and its ability to enhance P. infestans leaf colonisation. PiSFI3 is a 'WY-domain' RXLR effector that forms a novel trans-homodimer which is required for its ability to suppress PTI via interaction with the U-box-kinase protein StUBK.
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http://dx.doi.org/10.1111/nph.15635DOI Listing
April 2019

The oomycete microbe-associated molecular pattern Pep-13 triggers SERK3/BAK1-independent plant immunity.

Plant Cell Rep 2019 Feb 28;38(2):173-182. Epub 2018 Nov 28.

Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University (HZAU), Wuhan, 430070, People's Republic of China.

Key Message: Oomycetes MAMP Pep-13 can trigger SERK3/BAK1-independent PTI. Silencing of SERK3/BAK1 in solanaceous plants resulted in reduced expression of brassinosteroid marker genes and enhanced PTI transcriptional responses to Pep-13 treatment. To prevent disease, pattern recognition receptors (PRRs) are responsible for detecting microbe-associated molecular patterns (MAMPs) to switch on plant innate immunity. SOMATIC EMBROYOGENESIS KINASE 3 (SERK3)/BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1) is a well-characterized receptor-like kinase (RLK) that serves as a pivotal co-receptor with PRRs to activate immunity following recognition of MAMPs including flg22, EF-Tu, INF1 and XEG1. However, the requirement for SERK3/BAK1 in many pattern-triggered immune (PTI) signaling pathways is not yet known. Pep-13 is an oomycete MAMP that consists of a highly conserved motif (an oligopeptide of 13 amino acids) shared in Phytophthora transglutaminases. Quantitative RT-PCR analysis reveals that the transcripts of three PTI marker genes (WRKY7, WRKY8 and ACRE31) rapidly accumulate in response to three different MAMPs: flg22, chitin and Pep-13. Whereas silencing of SERK3/BAK1 in Nicotiana benthamiana or potato compromised transcript accumulation in response to flg22, it did not attenuate WRKY7, WRKY8 and ACRE31 up-regulation in response to chitin or Pep-13. This indicates that Pep-13 triggers immunity in a SERK3/BAK1-independent manner, similar to chitin. Surprisingly, silencing of SERK3/BAK1 led to significantly increased accumulation of PTI marker gene transcripts following Pep-13 or chitin treatment, compared to controls. This was accompanied by reduced expression of brassinosteroid (BR) marker genes StSTDH, StEXP8 and StCAB50 and StCHL1, which is a negative regulator of PTI, supporting previous reports that SERK3/BAK1-dependent BR signaling attenuates plant immunity. We provide Pep-13 as an alternative to chitin as a trigger of SERK3/BAK1-independent immunity.
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http://dx.doi.org/10.1007/s00299-018-2359-5DOI Listing
February 2019

Phytophthora infestans RXLR effectors act in concert at diverse subcellular locations to enhance host colonization.

J Exp Bot 2019 01;70(1):343-356

Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee, UK.

Oomycetes such as the potato blight pathogen Phytophthora infestans deliver RXLR effectors into plant cells to manipulate host processes and promote disease. Knowledge of where they localize inside host cells is important in understanding their function. Fifty-two P. infestans RXLR effectors (PiRXLRs) up-regulated during early stages of infection were expressed as fluorescent protein (FP) fusions inside cells of the model host Nicotiana benthamiana. FP-PiRXLR fusions were predominantly nucleo-cytoplasmic, nuclear, or plasma membrane-associated. Some also localized to the endoplasmic reticulum, mitochondria, peroxisomes, or microtubules, suggesting diverse sites of subcellular activity. Seven of the 25 PiRXLRs examined during infection accumulated at sites of haustorium penetration, probably due to co-localization with host target processes; Pi16663 (Avr1), for example, localized to Sec5-associated mobile bodies which showed perihaustorial accumulation. Forty-five FP-RXLR fusions enhanced pathogen leaf colonization when expressed in Nicotiana benthamiana, revealing that their presence was beneficial to infection. Co-expression of PiRXLRs that target and suppress different immune pathways resulted in an additive enhancement of colonization, indicating the potential to study effector combinations using transient expression assays. We provide a broad platform of high confidence P. infestans effector candidates from which to investigate the mechanisms, singly and in combination, by which this pathogen causes disease.
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http://dx.doi.org/10.1093/jxb/ery360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305197PMC
January 2019

Pathogen enrichment sequencing (PenSeq) enables population genomic studies in oomycetes.

New Phytol 2019 02 5;221(3):1634-1648. Epub 2018 Oct 5.

Cell and Molecular Sciences, The James Hutton Institute, Errol Road, Invergowrie, Dundee, DD2 5DA, UK.

The oomycete pathogens Phytophthora infestans and P. capsici cause significant crop losses world-wide, threatening food security. In each case, pathogenicity factors, called RXLR effectors, contribute to virulence. Some RXLRs are perceived by resistance proteins to trigger host immunity, but our understanding of the demographic processes and adaptive evolution of pathogen virulence remains poor. Here, we describe PenSeq, a highly efficient enrichment sequencing approach for genes encoding pathogenicity determinants which, as shown for the infamous potato blight pathogen Phytophthora infestans, make up < 1% of the entire genome. PenSeq facilitates the characterization of allelic diversity in pathogen effectors, enabling evolutionary and population genomic analyses of Phytophthora species. Furthermore, PenSeq enables the massively parallel identification of presence/absence variations and sequence polymorphisms in key pathogen genes, which is a prerequisite for the efficient deployment of host resistance genes. PenSeq represents a cost-effective alternative to whole-genome sequencing and addresses crucial limitations of current plant pathogen population studies, which are often based on selectively neutral markers and consequently have limited utility in the analysis of adaptive evolution. The approach can be adapted to diverse microbes and pathogens.
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http://dx.doi.org/10.1111/nph.15441DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6492278PMC
February 2019

The Haustorium Is a Site for Secretion of Diverse Classes of Infection-Associated Proteins.

mBio 2018 08 28;9(4). Epub 2018 Aug 28.

Division of Plant Sciences, University of Dundee (at The James Hutton Institute), Invergowrie, Dundee, United Kingdom

The oomycete potato blight pathogen secretes a diverse set of proteins to manipulate host plant immunity. However, there is limited knowledge about how and where they are secreted during infection. Here we used the endoplasmic reticulum (ER)-to-Golgi secretion pathway inhibitor brefeldin A (BFA) in combination with liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) to identify extracellular proteins from that were conventionally secreted from -cultured hyphae. We identified 19 proteins with predicted signal peptides that potentially influence plant interactions for which secretion was attenuated by BFA. In addition to inhibition by the apoplastic effector EPIC1, a cysteine protease inhibitor, we show that secretion of the cell wall-degrading pectinesterase enzyme PE1 and the icrobe-ssociated olecular attern (MAMP)-like elicitin INF4 was inhibited by BFA and , demonstrating that these proteins are secreted by the conventional, Golgi-mediated pathway. For comparison, secretion of a cytoplasmic RXLR (Arg-[any amino acid]-Leu-Arg) effector, Pi22926, was not inhibited by BFA. During infection, whereas INF4 accumulated outside the plant cell, RXLR effector Pi22926 entered the plant cell and accumulated in the nucleus. The effectors, the PE1 enzyme, and INF4 were all secreted from haustoria, pathogen structures that penetrate the plant cell wall to form an intimate interaction with the host plasma membrane. Our findings show the haustorium to be a major site of both conventional and nonconventional secretion of proteins with diverse functions during infection. There are many different classes of proteins secreted from that may influence or facilitate infection. Elucidating where and how they are secreted during infection is an important step toward developing methods to control their delivery processes. We used an inhibitor of conventional secretion to identify the following different classes of infection-associated extracellular proteins: cell wall-degrading and cell wall-modifying enzymes, microbe-associated molecular pattern-like proteins that may elicit immune responses, and apoplastic effectors that are predicted to suppress immunity. In contrast, secretion of a cytoplasmic effector that is translocated into host cells is nonconventional, as it is insensitive to inhibitor treatment. This evidence further supports the finding that proteins that are active in the apoplast and effector proteins that are active in the host cytoplasm are differentially secreted by Critically, it demonstrates that a disease-specific developmental structure, the haustorium, is a major secretion site for diverse protein classes during infection.
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http://dx.doi.org/10.1128/mBio.01216-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6113627PMC
August 2018

A potato STRUBBELIG-RECEPTOR FAMILY member, StLRPK1, associates with StSERK3A/BAK1 and activates immunity.

J Exp Bot 2018 11;69(22):5573-5586

Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, China.

Plant STRUBBELIG (SUB)-RECEPTOR FAMILY (SRF) genes encode putative leucine-rich repeat transmembrane receptor-like kinases. SRFs have been reported to play essential roles in tissue morphogenesis in many plant organs. Here, we show that a potato SRF family gene, StLRPK1, is involved in plant immunity. StLRPK1 is located at the cell plasma membrane and is strongly induced by culture filtrate from in vitro growth of the late blight pathogen Phytophthora infestans. Overexpression of StLRPK1 in stable transgenic potato or ectopic expression in Nicotiana benthamiana plants enhances P. infestans disease resistance, whereas RNA interference (RNAi) of StLRPK1 in potato decreases disease resistance. We found that StLRPK1 constitutively interacts with a pivotal co-receptor, SERK3A/BAK1, which plays a central role in plant immunity. Virus-induced gene silencing of SERK3A/BAK1 in N. benthamiana lines expressing StLRPK1 attenuated P. infestans resistance, indicating that SERK3A/BAK1 is required for StLRPK1-mediated immunity. Finally, we show that StLRPK1-triggered late blight resistance depends on the mitogen-activated protein kinase kinase MEK2 and mitogen-activated protein kinase WIPK. We propose a model in which StLRPK1 associates with SERK3A/BAK1 to positively regulate plant immunity to P. infestans through a MAPK cascade. These data provide new insights into our understanding of SRF function in plant immunity.
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http://dx.doi.org/10.1093/jxb/ery310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255708PMC
November 2018

Plant pathogen effector utilizes host susceptibility factor NRL1 to degrade the immune regulator SWAP70.

Proc Natl Acad Sci U S A 2018 08 26;115(33):E7834-E7843. Epub 2018 Jul 26.

Division of Plant Science, James Hutton Institute, University of Dundee, Invergowrie, DD2 5DA Dundee, United Kingdom;

Plant pathogens deliver effectors into plant cells to suppress immunity. Whereas many effectors inactivate positive immune regulators, other effectors associate with negative regulators of immunity: so-called susceptibility (S) factors. Little is known about how pathogens exploit S factors to suppress immunity. RXLR effector Pi02860 interacts with host protein NRL1, which is an S factor whose activity suppresses INF1-triggered cell death (ICD) and is required for late blight disease. We show that NRL1 interacts in yeast and with a guanine nucleotide exchange factor called SWAP70. SWAP70 associates with endosomes and is a positive regulator of immunity. Virus-induced gene silencing of in enhances colonization and compromises ICD. In contrast, transient overexpression of SWAP70 reduces infection and accelerates ICD. Expression of Pi02860 and NRL1, singly or in combination, results in proteasome-mediated degradation of SWAP70. Degradation of SWAP70 is prevented by silencing , or by mutation of Pi02860 to abolish its interaction with NRL1. NRL1 is a BTB-domain protein predicted to form the substrate adaptor component of a CULLIN3 ubiquitin E3 ligase. A dimerization-deficient mutant, NRL1, fails to interact with SWAP70 but maintains its interaction with Pi02860. NRL1 acts as a dominant-negative mutant, preventing SWAP70 degradation in the presence of effector Pi02860, and reducing infection. Critically, Pi02860 enhances the association between NRL1 and SWAP70 to promote proteasome-mediated degradation of the latter and, thus, suppress immunity. Preventing degradation of SWAP70 represents a strategy to combat late blight disease.
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http://dx.doi.org/10.1073/pnas.1808585115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6099861PMC
August 2018

Phytophthora infestans RXLR effector SFI5 requires association with calmodulin for PTI/MTI suppressing activity.

New Phytol 2018 09 22;219(4):1433-1446. Epub 2018 Jun 22.

Department of Biochemistry, Centre for Plant Molecular Biology, Eberhard Karls University, Auf der Morgenstelle 32, D-72076, Tübingen, Germany.

Pathogens secrete effector proteins to interfere with plant innate immunity, in which Ca /calmodulin (CaM) signalling plays key roles. Thus far, few effectors have been identified that directly interact with CaM for defence suppression. Here, we report that SFI5, an RXLR effector from Phytophthora infestans, suppresses microbe-associated molecular pattern (MAMP)-triggered immunity (MTI) by interacting with host CaMs. We predicted the CaM-binding site in SFI5 using in silico analysis. The interaction between SFI5 and CaM was tested by both in vitro and in vivo assays. MTI suppression by SFI5 and truncated variants were performed in a tomato protoplast system. We found that both the predicted CaM-binding site and the full-length SFI5 protein interact with CaM in the presence of Ca . MTI responses, such as FRK1 upregulation, reactive oxygen species accumulation, and mitogen-activated protein kinase activation were suppressed by truncated SFI5 proteins containing the C-terminal CaM-binding site but not by those without it. The plasma membrane localization of SFI5 and its ability to enhance infection were also perturbed by loss of the CaM-binding site. We conclude that CaM-binding is required for localization and activity of SFI5. We propose that SFI5 suppresses plant immunity by interfering with immune signalling components after activation by CaMs.
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http://dx.doi.org/10.1111/nph.15250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6099356PMC
September 2018

Effector gene birth in plant parasitic nematodes: Neofunctionalization of a housekeeping glutathione synthetase gene.

PLoS Genet 2018 04 11;14(4):e1007310. Epub 2018 Apr 11.

Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, United Kingdom.

Plant pathogens and parasites are a major threat to global food security. Plant parasitism has arisen four times independently within the phylum Nematoda, resulting in at least one parasite of every major food crop in the world. Some species within the most economically important order (Tylenchida) secrete proteins termed effectors into their host during infection to re-programme host development and immunity. The precise detail of how nematodes evolve new effectors is not clear. Here we reconstruct the evolutionary history of a novel effector gene family. We show that during the evolution of plant parasitism in the Tylenchida, the housekeeping glutathione synthetase (GS) gene was extensively replicated. New GS paralogues acquired multiple dorsal gland promoter elements, altered spatial expression to the secretory dorsal gland, altered temporal expression to primarily parasitic stages, and gained a signal peptide for secretion. The gene products are delivered into the host plant cell during infection, giving rise to "GS-like effectors". Remarkably, by solving the structure of GS-like effectors we show that during this process they have also diversified in biochemical activity, and likely represent the founding members of a novel class of GS-like enzyme. Our results demonstrate the re-purposing of an endogenous housekeeping gene to form a family of effectors with modified functions. We anticipate that our discovery will be a blueprint to understand the evolution of other plant-parasitic nematode effectors, and the foundation to uncover a novel enzymatic function.
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http://dx.doi.org/10.1371/journal.pgen.1007310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5919673PMC
April 2018

The Potato MAP3K StVIK Is Required for the RXLR Effector Pi17316 to Promote Disease.

Plant Physiol 2018 05 27;177(1):398-410. Epub 2018 Mar 27.

Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom

Plant pathogens deliver effectors to manipulate processes in their hosts, creating a suitable environment for invasion and proliferation. Yet, little is known about the host proteins that are targeted by effectors from filamentous pathogens. Here, we show that stable transgenic expression in potato () and transient expression in of the arginine-any amino acid-leucine-arginine effector Pi17316 enhances leaf colonization by the late blight pathogen Expression of Pi17316 also attenuates cell death triggered by the pathogen-associated molecular pattern Infestin1 (INF1), indicating that the effector suppresses pattern-triggered immunity. However, this effector does not attenuate cell death triggered by a range of resistance proteins, showing that it specifically suppresses INF1-triggered cell death (ICD). In yeast two-hybrid assays, Pi17316 interacts directly with the potato ortholog of VASCULAR HIGHWAY1-interacting kinase (StVIK), encoding a predicted MEK kinase (MAP3K). Interaction in planta was confirmed by coimmunoprecipitation and occurs at the plant plasma membrane. Virus-induced gene silencing of in attenuated colonization, whereas transient overexpression of enhanced colonization, indicating that this host protein acts as a susceptibility factor. Moreover, overexpression specifically attenuated ICD, indicating that it is a negative regulator of immunity. The abilities of Pi17316 to enhance colonization or suppress ICD were compromised significantly in -silenced plants, demonstrating that the effector activity of Pi17316 is mediated by this MAP3K. Thus, StVIK is exploited by as a susceptibility factor to promote late blight disease.
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http://dx.doi.org/10.1104/pp.18.00028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5933144PMC
May 2018

Why did filamentous plant pathogens evolve the potential to secrete hundreds of effectors to enable disease?

Mol Plant Pathol 2018 04;19(4):781-785

Institute for Biology I, Unit of Plant Molecular Cell Biology, RWTH Aachen University, 52056 Aachen, Germany.

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http://dx.doi.org/10.1111/mpp.12649DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638121PMC
April 2018

Delivery of cytoplasmic and apoplastic effectors from Phytophthora infestans haustoria by distinct secretion pathways.

New Phytol 2017 Oct 31;216(1):205-215. Epub 2017 Jul 31.

Division of Plant Sciences, University of Dundee (at JHI), Errol Road, Invergowrie, Dundee, DD2 5DA, UK.

The potato blight pathogen Phytophthora infestans secretes effector proteins that are delivered inside (cytoplasmic) or can act outside (apoplastic) plant cells to neutralize host immunity. Little is known about how and where effectors are secreted during infection, yet such knowledge is essential to understand and combat crop disease. We used transient Agrobacterium tumefaciens-mediated in planta expression, transformation of P. infestans with fluorescent protein fusions and confocal microscopy to investigate delivery of effectors to plant cells during infection. The cytoplasmic effector Pi04314, expressed as a monomeric red fluorescent protein (mRFP) fusion protein with a signal peptide to secrete it from plant cells, did not passively re-enter the cells upon secretion. However, Pi04314-mRFP expressed in P. infestans was translocated from haustoria, which form intimate interactions with plant cells, to accumulate at its sites of action in the host nucleus. The well-characterized apoplastic effector EPIC1, a cysteine protease inhibitor, was also secreted from haustoria. EPIC1 secretion was inhibited by brefeldin A (BFA), demonstrating that it is delivered by conventional Golgi-mediated secretion. By contrast, Pi04314 secretion was insensitive to BFA treatment, indicating that the cytoplasmic effector follows an alternative route for delivery into plant cells. Phytophthora infestans haustoria are thus sites for delivery of both apoplastic and cytoplasmic effectors during infection, following distinct secretion pathways.
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http://dx.doi.org/10.1111/nph.14696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5601276PMC
October 2017

A new proteinaceous pathogen-associated molecular pattern (PAMP) identified in Ascomycete fungi induces cell death in Solanaceae.

New Phytol 2017 Jun 7;214(4):1657-1672. Epub 2017 Apr 7.

Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.

Pathogen-associated molecular patterns (PAMPs) are detected by plant pattern recognition receptors (PRRs), which gives rise to PAMP-triggered immunity (PTI). We characterized a novel fungal PAMP, Cell Death Inducing 1 (RcCDI1), identified in the Rhynchosporium commune transcriptome sampled at an early stage of barley (Hordeum vulgare) infection. The ability of RcCDI1 and its homologues from different fungal species to induce cell death in Nicotiana benthamiana was tested following agroinfiltration or infiltration of recombinant proteins produced by Pichia pastoris. Virus-induced gene silencing (VIGS) and transient expression of Phytophthora infestans effectors PiAVR3a and PexRD2 were used to assess the involvement of known components of PTI in N. benthamiana responses to RcCDI1. RcCDI1 was highly upregulated early during barley colonization with R. commune. RcCDI1 and its homologues from different fungal species, including Zymoseptoria tritici, Magnaporthe oryzae and Neurospora crassa, exhibited PAMP activity, inducing cell death in Solanaceae but not in other families of dicots or monocots. RcCDI1-triggered cell death was shown to require N. benthamiana Brassinosteroid insensitive 1-Associated Kinase 1 (NbBAK1), N. benthamiana suppressor of BIR1-1 (NbSOBIR1) and N. benthamiana SGT1 (NbSGT1), but was not suppressed by PiAVR3a or PexRD2. We report the identification of a novel Ascomycete PAMP, RcCDI1, recognized by Solanaceae but not by monocots, which activates cell death through a pathway that is distinct from that triggered by the oomycete PAMP INF1.
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http://dx.doi.org/10.1111/nph.14542DOI Listing
June 2017

RXLR Effector AVR2 Up-Regulates a Brassinosteroid-Responsive bHLH Transcription Factor to Suppress Immunity.

Plant Physiol 2017 May 7;174(1):356-369. Epub 2017 Mar 7.

Cell and Molecular Science, James Hutton Institute (D.T., L.Y., S.N., L.W., J.S., J.M., P.C.B., P.E.H., P.R.J.B., E.M.G.), and Division of Plant Science, School of Life Science (at The James Hutton institute) (D.T., L.Y., S.N., P.R.J.B.), University of Dundee Invergowrie, Dundee, DD2 5DA, United Kingdom;

An emerging area in plant research focuses on antagonism between regulatory systems governing growth and immunity. Such cross talk represents a point of vulnerability for pathogens to exploit. AVR2, an RXLR effector secreted by the potato blight pathogen , interacts with potato BSL1, a putative phosphatase implicated in growth-promoting brassinosteroid (BR) hormone signaling. Transgenic potato () plants expressing the effector exhibit transcriptional and phenotypic hallmarks of overactive BR signaling and show enhanced susceptibility to Microarray analysis was used to identify a set of BR-responsive marker genes in potato, all of which are constitutively expressed to BR-induced levels in AVR2 transgenic lines. One of these genes was a bHLH transcription factor, designated , homologous to and , which are known to facilitate antagonism between BR and immune responses. Transient expression of either AVR2 or CHL1 enhanced leaf colonization by and compromised immune cell death activated by perception of the elicitin Infestin1 (INF1). Knockdown of transcript using Virus-Induced Gene Silencing (VIGS) reduced colonization of on Moreover, the ability of AVR2 to suppress INF1-triggered cell death was attenuated in -silenced plants, indicating that NbCHL1 was important for this effector activity. Thus, AVR2 exploits cross talk between BR signaling and innate immunity in species, representing a novel, indirect mode of innate immune suppression by a filamentous pathogen effector.
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http://dx.doi.org/10.1104/pp.16.01804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5411136PMC
May 2017

RNA-seq Profiling Reveals Defense Responses in a Tolerant Potato Cultivar to Stem Infection by ssp. .

Front Plant Sci 2016 20;7:1905. Epub 2016 Dec 20.

Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute, Genomics Research Institute, University of Pretoria Pretoria, South Africa.

subsp. is a member of the soft rot Enterobacteriaceae (SRE) family that causes tuber soft rot and blackleg diseases of stems in potato plants. Currently, there are no effective chemical strategies for the control of members of the SRE. Thus, an understanding of the inducible defense responses in stems of potato plants is important, particularly during colonization of the vascular system. Here, time-course RNA-sequencing analysis was used to compare expressed genes between a susceptible potato cultivar ( cv Valor) and a tolerant cultivar ( cv BP1) at 0, 6, 12, 24, and 72 h post-inoculation with . In total, we identified 6139 and 8214 differentially expressed genes (DEGs) in the tolerant and susceptible cultivars, compared to mock-inoculated controls, respectively. Key DEGs distinguishing between tolerance and susceptibility were associated with negative regulation of cell death and plant-type cell wall organization/biogenesis biological processes in the tolerant and susceptible cultivars, respectively. Among these were DEGs involved in signaling (mainly MAPK cascade and ethylene pathway), defense-related transcription regulation including WRKY transcription factors, and downstream secondary cell biosynthesis. Together, our results suggest that cv BP1 likely employs quantitative defense response against . Overall, our study provides the first transcriptome-wide insight into the molecular basis of tolerance and/or resistance of potato stems to SRE infection.
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http://dx.doi.org/10.3389/fpls.2016.01905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5167753PMC
December 2016

BTB-BACK Domain Protein POB1 Suppresses Immune Cell Death by Targeting Ubiquitin E3 ligase PUB17 for Degradation.

PLoS Genet 2017 01 5;13(1):e1006540. Epub 2017 Jan 5.

School of Biological and Biomedical Sciences, Durham University, United Kingdom.

Hypersensitive response programmed cell death (HR-PCD) is a critical feature in plant immunity required for pathogen restriction and prevention of disease development. The precise control of this process is paramount to cell survival and an effective immune response. The discovery of new components that function to suppress HR-PCD will be instrumental in understanding the regulation of this fundamental mechanism. Here we report the identification and characterisation of a BTB domain E3 ligase protein, POB1, that functions to suppress HR-PCD triggered by evolutionarily diverse pathogens. Nicotiana benthamiana and tobacco plants with reduced POB1 activity show accelerated HR-PCD whilst those with increased POB1 levels show attenuated HR-PCD. We demonstrate that POB1 dimerization and nuclear localization are vital for its function in HR-PCD suppression. Using protein-protein interaction assays, we identify the Plant U-Box E3 ligase PUB17, a well established positive regulator of plant innate immunity, as a target for POB1-mediated proteasomal degradation. Using confocal imaging and in planta immunoprecipitation assays we show that POB1 interacts with PUB17 in the nucleus and stimulates its degradation. Mutated versions of POB1 that show reduced interaction with PUB17 fail to suppress HR-PCD, indicating that POB1-mediated degradation of PUB17 U-box E3 ligase is an important step for negative regulation of specific immune pathways in plants. Our data reveals a new mechanism for BTB domain proteins in suppressing HR-PCD in plant innate immune responses.
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http://dx.doi.org/10.1371/journal.pgen.1006540DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5249250PMC
January 2017

Opening the Effector Protein Toolbox for Plant-Parasitic Cyst Nematode Interactions.

Mol Plant 2016 11 28;9(11):1451-1453. Epub 2016 Sep 28.

Division of Plant Sciences, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

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http://dx.doi.org/10.1016/j.molp.2016.09.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5106285PMC
November 2016

Genome-wide identification of potato long intergenic noncoding RNAs responsive to Pectobacterium carotovorum subspecies brasiliense infection.

BMC Genomics 2016 08 11;17(1):614. Epub 2016 Aug 11.

Forestry and Agricultural Biotechnology Institute (FABI), Genomics Research Institute (GRI), Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, 0028, South Africa.

Background: Long noncoding RNAs (lncRNAs) represent a class of RNA molecules that are implicated in regulation of gene expression in both mammals and plants. While much progress has been made in determining the biological functions of lncRNAs in mammals, the functional roles of lncRNAs in plants are still poorly understood. Specifically, the roles of long intergenic nocoding RNAs (lincRNAs) in plant defence responses are yet to be fully explored.

Results: In this study, we used strand-specific RNA sequencing to identify 1113 lincRNAs in potato (Solanum tuberosum) from stem tissues. The lincRNAs are expressed from all 12 potato chromosomes and generally smaller in size compared to protein-coding genes. Like in other plants, most potato lincRNAs possess single exons. A time-course RNA-seq analysis between a tolerant and a susceptible potato cultivar showed that 559 lincRNAs are responsive to Pectobacterium carotovorum subsp. brasiliense challenge compared to mock-inoculated controls. Moreover, coexpression analysis revealed that 17 of these lincRNAs are highly associated with 12 potato defence-related genes.

Conclusions: Together, these results suggest that lincRNAs have potential functional roles in potato defence responses. Furthermore, this work provides the first library of potato lincRNAs and a set of novel lincRNAs implicated in potato defences against P. carotovorum subsp. brasiliense, a member of the soft rot Enterobacteriaceae phytopathogens.
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http://dx.doi.org/10.1186/s12864-016-2967-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4982125PMC
August 2016

Utilizing "Omic" Technologies to Identify and Prioritize Novel Sources of Resistance to the Oomycete Pathogen Phytophthora infestans in Potato Germplasm Collections.

Front Plant Sci 2016 27;7:672. Epub 2016 May 27.

Cell and Molecular Sciences, The James Hutton Institute Dundee, UK.

The greatest threat to potato production world-wide is late blight, caused by the oomycete pathogen Phytophthora infestans. A screen of 126 wild diploid Solanum accessions from the Commonwealth Potato Collection (CPC) with P. infestans isolates belonging to the genotype 13-A2 identified resistances in the species S. bulbocastanum, S. capsicibaccatum, S. microdontum, S. mochiquense, S. okadae, S. pinnatisectum, S. polyadenium, S. tarijense, and S. verrucosum. Effector-omics, allele mining, and diagnostic RenSeq (dRenSeq) were utilized to investigate the nature of resistances in S. okadae accessions. dRenSeq in resistant S. okadae accessions 7129, 7625, 3762, and a bulk of 20 resistant progeny confirmed the presence of full-length Rpi-vnt1.1 under stringent mapping conditions and corroborated allele mining results in the accessions 7129 and 7625 as well as Avr-vnt1 recognition in transient expression assays. In contrast, susceptible S. okadae accession 3761 and a bulk of 20 susceptible progeny lacked sequence homology in the 5' end compared to the functional Rpi-vnt1.1 gene. Further evaluation of S. okadae accessions with P. infestans isolates that have a broad spectrum of virulence demonstrated that, although S. okadae accessions 7129, 7625, and 7629 contain functional Rpi-vnt1.1, they also carry a novel resistance gene. We provide evidence that existing germplasm collections are important sources of novel resistances and that "omic" technologies such as dRenSeq-based genomics and effector-omics are efficacious tools to rapidly explore the diversity within these collections.
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http://dx.doi.org/10.3389/fpls.2016.00672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882398PMC
June 2016

Oomycetes Seek Help from the Plant: Phytophthora infestans Effectors Target Host Susceptibility Factors.

Mol Plant 2016 05 16;9(5):636-638. Epub 2016 Apr 16.

Cell and Molecular Science, James Hutton Institute (JHI), Invergowrie, Dundee DD2 5DA, UK; Division of Plant Science, College of Life Science, University of Dundee (at JHI), Invergowrie, Dundee DD2 5DA, UK. Electronic address:

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http://dx.doi.org/10.1016/j.molp.2016.04.005DOI Listing
May 2016

Potato NPH3/RPT2-Like Protein StNRL1, Targeted by a Phytophthora infestans RXLR Effector, Is a Susceptibility Factor.

Plant Physiol 2016 05 10;171(1):645-57. Epub 2016 Mar 10.

Fujian Key Laboratory of Plant Virology, Institute of Plant Virology, Fujian Agricultural and Forestry University, Fuzhou, Fujian 350002, China (L.Y., J.Z.);Cell and Molecular Science, James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom (L.Y., S.N., P.C.B., M.A., L.M.G., E.M.G., P.R.J.B.);Dundee Effector Consortium, Invergowrie, Dundee DD2 5DA, United Kingdom (L.Y., H.M., S.N., Q.H., P.C.B., M.A., L.M.G., E.M.G., P.R.J.B.);Division of Plant Science, School of Life Science, University of Dundee, Invergowrie, Dundee DD2 5DA, United Kingdom (L.Y., H.M., Q.H., M.A., P.R.J.B.); andKey Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, China (Q.H., W.Z., Z.T.)

Plant pathogens deliver effectors to manipulate host processes. We know little about how fungal and oomycete effectors target host proteins to promote susceptibility, yet such knowledge is vital to understand crop disease. We show that either transient expression in Nicotiana benthamiana, or stable transgenic expression in potato (Solanum tuberosum), of the Phytophthora infestans RXLR effector Pi02860 enhances leaf colonization by the pathogen. Expression of Pi02860 also attenuates cell death triggered by the P. infestans microbe-associated molecular pattern INF1, indicating that the effector suppresses pattern-triggered immunity. However, the effector does not attenuate cell death triggered by Cf4/Avr4 coexpression, showing that it does not suppress all cell death activated by cell surface receptors. Pi02860 interacts in yeast two-hybrid assays with potato NPH3/RPT2-LIKE1 (NRL1), a predicted CULLIN3-associated ubiquitin E3 ligase. Interaction of Pi02860 in planta was confirmed by coimmunoprecipitation and bimolecular fluorescence complementation assays. Virus-induced gene silencing of NRL1 in N. benthamiana resulted in reduced P. infestans colonization and accelerated INF1-mediated cell death, indicating that this host protein acts as a negative regulator of immunity. Moreover, whereas NRL1 virus-induced gene silencing had no effect on the ability of the P. infestans effector Avr3a to suppress INF1-mediated cell death, such suppression by Pi02860 was significantly attenuated, indicating that this activity of Pi02860 is mediated by NRL1. Transient overexpression of NRL1 resulted in the suppression of INF1-mediated cell death and enhanced P. infestans leaf colonization, demonstrating that NRL1 acts as a susceptibility factor to promote late blight disease.
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http://dx.doi.org/10.1104/pp.16.00178DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854710PMC
May 2016

A Phytophthora infestans RXLR effector targets plant PP1c isoforms that promote late blight disease.

Nat Commun 2016 Jan 29;7:10311. Epub 2016 Jan 29.

Department of Cell and Molecular Sciences, James Hutton Institute, Errol Road, Invergowrie, Dundee DD2 5DA, UK.

Plant pathogens deliver effectors to alter host processes. Knowledge of how effectors target and manipulate host proteins is critical to understand crop disease. Here, we show that in planta expression of the RXLR effector Pi04314 enhances leaf colonization by Phytophthora infestans via activity in the host nucleus and attenuates induction of jasmonic and salicylic acid-responsive genes. Pi04314 interacts with three host protein phosphatase 1 catalytic (PP1c) isoforms, causing their re-localization from the nucleolus to the nucleoplasm. Re-localization of PP1c-1 also occurs during infection and is dependent on an R/KVxF motif in the effector. Silencing the PP1c isoforms or overexpression of a phosphatase-dead PP1c-1 mutant attenuates infection, demonstrating that host PP1c activity is required for disease. Moreover, expression of PP1c-1mut abolishes enhanced leaf colonization mediated by in planta Pi04314 expression. We argue that PP1c isoforms are susceptibility factors forming holoenzymes with Pi04314 to promote late blight disease.
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http://dx.doi.org/10.1038/ncomms10311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740116PMC
January 2016

Discovery and profiling of small RNAs responsive to stress conditions in the plant pathogen Pectobacterium atrosepticum.

BMC Genomics 2016 Jan 12;17:47. Epub 2016 Jan 12.

Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa.

Background: Small RNAs (sRNAs) have emerged as important regulatory molecules and have been studied in several bacteria. However, to date, there have been no whole-transcriptome studies on sRNAs in any of the Soft Rot Enterobacteriaceae (SRE) group of pathogens. Although the main ecological niches for these pathogens are plants, a significant part of their life cycle is undertaken outside their host within adverse soil environment. However, the mechanisms of SRE adaptation to this harsh nutrient-deficient environment are poorly understood.

Results: In the study reported herein, by using strand-specific RNA-seq analysis and in silico sRNA predictions, we describe the sRNA pool of Pectobacterium atrosepticum and reveal numerous sRNA candidates, including those that are induced during starvation-activated stress responses. Consequently, strand-specific RNA-seq enabled detection of 137 sRNAs and sRNA candidates under starvation conditions; 25 of these sRNAs were predicted for this bacterium in silico. Functional annotations were computationally assigned to 68 sRNAs. The expression of sRNAs in P. atrosepticum was compared under growth-promoting and starvation conditions: 68 sRNAs were differentially expressed with 47 sRNAs up-regulated under nutrient-deficient conditions. Conservation analysis using BLAST showed that most of the identified sRNAs are conserved within the SRE. Subsequently, we identified 9 novel sRNAs within the P. atrosepticum genome.

Conclusions: Since many of the identified sRNAs are starvation-induced, the results of our study suggests that sRNAs play key roles in bacterial adaptive response. Finally, this work provides a basis for future experimental characterization and validation of sRNAs in plant pathogens.
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http://dx.doi.org/10.1186/s12864-016-2376-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4710047PMC
January 2016

A transcriptional reference map of defence hormone responses in potato.

Sci Rep 2015 Oct 19;5:15229. Epub 2015 Oct 19.

The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.

Phytohormones are involved in diverse aspects of plant life including the regulation of plant growth, development and reproduction, as well as governing biotic and abiotic stress responses. We have generated a comprehensive transcriptional reference map of the early potato responses to exogenous application of the defence hormones abscisic acid, brassinolides (applied as epibrassinolide), ethylene (applied as the ethylene precursor aminocyclopropanecarboxylic acid), salicylic acid and jasmonic acid (applied as methyl jasmonate). Of the 39000 predicted genes on the microarray, a total of 2677 and 2473 genes were significantly differentially expressed at 1 h and 6 h after hormone treatment, respectively. Specific marker genes newly identified for the early hormone responses in potato include: a homeodomain 20 transcription factor (DMG400000248) for abscisic acid; a SAUR gene (DMG400016561) induced in epibrassinolide treated plants; an osmotin gene (DMG400003057) specifically enhanced by aminocyclopropanecarboxylic acid; a gene weakly similar to AtWRKY40 (DMG402007388) that was induced by salicylic acid; and a jasmonate ZIM-domain protein 1 (DMG400002930) which was specifically activated by methyl jasmonate. An online database has been set up to query the expression patterns of potato genes represented on the microarray that can also incorporate future microarray or RNAseq-based expression studies.
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http://dx.doi.org/10.1038/srep15229DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4610000PMC
October 2015