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Cellular Microbiol: Consequences of flagellin export through the type III secretion system of Pseudomonas syringae reveal a major difference in the innate immune systems of mammals and plants (2012)

Cellular Microbiol: Consequences of flagellin export through the type III secretion system of Pseudomonas syringae reveal a major difference in the innate immune systems of mammals and plants (2012) | Plants and Microbes | Scoop.it

Bacterial flagellin is perceived as a microbe (or pathogen)-associated molecular pattern (MAMP or PAMP) by the extracellular pattern recognition receptors, FLS2 and TLR5, of plants and mammals, respectively. Flagellin accidently translocated into mammalian cells by pathogen type III secretion systems (T3SSs) is recognized by nucleotide-binding leucine-rich repeat receptor NLRC4 as a pattern of pathogenesis and induces a death-associated immune response. The nonpathogen Pseudomonas fluorescens Pf0-1, expressing a Pseudomonas syringae T3SS, and the plant pathogen P. syringae pv. tomato DC3000 were used to seek evidence of an analogous cytoplasmic recognition system for flagellin in the model plant Nicotiana benthamiana. Flagellin (FliC) was secreted in culture and translocated into plant cells by the T3SS expressed in Pf0-1 and DC3000 and in their ΔflgGHI flagellar pathway mutants. ΔfliC and ΔflgGHI mutants of Pf0-1 and DC3000 were strongly reduced in elicitation of reactive oxygen species production and in immunity induction as indicated by the ability of challenge bacteria inoculated 6 h later to translocate a type III effector-reporter and to elicit effector-triggered cell death. Agrobacterium-mediated transient expression in N. benthamiana of FliC with or without a eukaryotic export signal peptide, coupled with virus-induced gene silencing of FLS2, revealed no immune response that was not FLS2 dependent. Transiently expressed FliC from DC3000 and Pectobacterium carotovorum did not induce cell death in N. benthamiana, tobacco, or tomato leaves. Flagellin is the major Pseudomonas MAMP perceived by N. benthamiana, and although flagellin secretion through the plant cell wall by the T3SS may partially contribute to FLS2-dependent immunity, flagellin in the cytosol does not elicit immune-associated cell death. We postulate that a death response to translocated MAMPs would produce vulnerability to the many necrotrophic pathogens of plants, such as P. carotovorum, which differ from P. syringae and other (hemi)biotrophic pathogens in benefitting from death-associated immune responses.


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News: Longping to stop selling super-hybrid rice variety (2015)

News: Longping to stop selling super-hybrid rice variety (2015) | Plants and Microbes | Scoop.it

Yuan Longping High-Tech Agriculture Co Ltd said on Monday that it would stop selling its hybrid rice variety "Liangyou 0293", following a massive crop failure in Anhui province in eastern China, where it was largely cultivated.


"Sales of the 'Liangyou 0293' variety fetched about 7 million yuan ($1.1 million) for the company last year. The latest move is certain to hit profit this year," the listed company, known as Longping High-Tech, said in a regulatory filing.


More than 667 hectares of rice fields in six cities in Anhui province suffered low-yields or even outright crop failure last October due to rice blast, a serious disease caused by the imperfect fungus, according to the provincial seed management station.


Some counties such as Wuhe, one of the rice-producing areas, were hit hard with the yield of rice plummeting to 50 kilograms per mu (0.06 hectare) or to even none, from the expected 500 kilograms.


"I did my best but only a few bags of rice were harvested," said Wang Peijie, a local farmer. "It is almost nothing."


Local farmers said misleading advertisements were to blame for their heavy losses.


On the packages of seeds sold to farmers, the ad claimed the strain had a resistance of 5.6 grades, which indicates an incidence rate of only 25 percent, but inside, a piece of paper showed that the seeds had a resistance of 9 grades, suggesting the possibility of catching a disease is as high as 100 percent, a report from the Guangzhou-based Southern Weekly said.


However, Longping High-Tech said that it was mainly the natural conditions including low temperatures and rains in the rice-growing regions that had led to the rice blast outbreak.


"The variety has been grown in the region for six years, and during the period rice blast had never occurred," according to the statement.


"We are sorry for the losses to farmers ... and insurance companies will take care of that."

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MPMI: Synergistic Interactions of the Plant Cell Death Pathways Induced by Phytophthora infestans Nep1-Like Protein PiNPP1.1 and INF1 Elicitin (2006)

MPMI: Synergistic Interactions of the Plant Cell Death Pathways Induced by Phytophthora infestans Nep1-Like Protein PiNPP1.1 and INF1 Elicitin (2006) | Plants and Microbes | Scoop.it

Cell death plays a ubiquitous role in plant-microbe interactions, given that it is associated with both susceptible and resistance interactions. A class of cell death-inducing proteins, termed Nep1-like proteins (NLPs), has been reported in bacteria, fungi, and oomycetes. These proteins induce nonspecific necrosis in a variety of dicotyledonous plants. Here, we describe three members of the NLP family from the oomycete Phytophthora infestans (PiNPP1.1, PiNPP1.2, and PiNPP1.3). Using agroinfection with a binary Potato virus X vector, we showed that PiNPP1.1 induces cell death in Nicotiana benthamiana and the host plant tomato. Expression analyses indicated that PiNPP1.1 is up-regulated during late stages of infection of tomato by P. infestans. We compared PiNPP1.1 necrosis-inducing activity to INF1 elicitin, a well-studied protein that triggers the hypersensitive response in Nicotiana spp. Using virus-induced gene silencing, we showed that the cell death induced by PiNPP1.1 is dependent on the ubiquitin ligase-associated protein SGT1 and the heat-shock protein HSP90. In addition, cell death triggered by PiNPP1.1 but not that by INF1 was dependent on the defense-signaling proteins COI1, MEK2, NPR1, and TGA2.2, suggesting distinct signaling requirements. Combined expression of PiNPP1.1 and INF1 in N. benthamiana resulted in enhanced cell death, suggesting synergistic interplay between the two cell-death responses. Altogether, these results point to potentially distinct but interacting cell-death pathways induced by PiNPP1.1 and INF1 in plants.

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Mol Plant Pathol: Transcriptional Dynamics of Phytophthora infestans During Sequential Stages of Hemibiotrophic Infection of Tomato (2015)

Mol Plant Pathol: Transcriptional Dynamics of Phytophthora infestans During Sequential Stages of Hemibiotrophic Infection of Tomato (2015) | Plants and Microbes | Scoop.it

Hemibiotrophic plant pathogens, such as the oomycete Phytophthora infestans, employ a biphasic infection strategy, initially behaving as biotrophs where minimal symptoms are exhibited by the plant, and subsequently as necrotrophs, feeding on dead plant tissue. The regulation of this transition and the breadth of molecular mechanisms that modulate plant defenses are not well understood, although effector proteins secreted by the pathogen are thought to play a key role. We examined the transcriptional dynamics of P. infestans in a compatible interaction with its host tomato (Solanum lycopersicum), at three infection stages: biotrophy; the transition from biotrophy to necrotrophy; and necrotrophy. The expression data suggested a tight temporal regulation of many pathways associated with suppression of plant defense mechanisms and pathogenicity, including the induction of putative cytoplasmic and apoplastic effectors. Twelve of these were experimentally evaluated to determine their ability to suppress necrosis caused by the P. infestans necrosis-inducing protein PiNPP1.1 in Nicotiana benthamiana. Four effectors suppressed necrosis, suggesting that they might prolong the biotrophic phase. This study suggests that a complex regulation of effector expression modulates the outcome of the interaction.


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BES Symposium: The Ecology and Evolution of Emerging Plant Pests and Pathogens: Challenges to Global Food Security and Ecosystem Resilience, 13–14 July, 2015, Cornwall, UK

BES Symposium: The Ecology and Evolution of Emerging Plant Pests and Pathogens: Challenges to Global Food Security and Ecosystem Resilience, 13–14 July, 2015, Cornwall, UK | Plants and Microbes | Scoop.it
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MPMI: A recent expansion of the RXLR effector gene Avrblb2 is maintained in global populations of Phytophthora infestans indicating different contributions to virulence (2015)

MPMI: A recent expansion of the RXLR effector gene Avrblb2 is maintained in global populations of Phytophthora infestans indicating different contributions to virulence (2015) | Plants and Microbes | Scoop.it

The introgression of disease resistance (R) genes encoding immunoreceptors with broad-spectrum recognition into cultivated potato appears to be the most promising approach to achieve sustainable management of late blight caused by the oomycete pathogen Phytophthora infestans. Rpi-blb2 from Solanum bulbocastanum, shows great potential for use in agriculture based on preliminary potato disease trials. Rpi-blb2 confers immunity by recognizing the P. infestans avirulence effector protein AVRblb2 after it is translocated inside the plant cell. This effector belongs to the RXLR class of effectors and is under strong positive selection. Structure-function analyses revealed a key polymorphic amino acid (position 69) in AVRblb2 effector that is critical for activation of Rpi-blb2. In this study, we reconstructed the evolutionary history of the Avrblb2 gene family and further characterized its genetic structure in worldwide populations. Our data indicates that Avrblb2 evolved as a single copy gene in a putative ancestral species of P. infestans and has recently expanded in the Phytophthora species that infect solanaceous hosts. As a consequence, at least four variants of AVRblb2 arose in P. infestans. One of these variants, with a Phe residue at position 69, evades recognition by the cognate resistance gene. Surprisingly, all Avrblb2 variants are maintained in pathogen populations. This suggests a potential benefit for the pathogen in preserving duplicated versions of AVRblb2 possibly because the variants may have different contributions to pathogen fitness in a diversified solanaceous host environment.

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Plant Cell: A Secreted Effector Protein of Ustilago maydis Guides Maize Leaf Cells to Form Tumors (2015)

Plant Cell: A Secreted Effector Protein of Ustilago maydis Guides Maize Leaf Cells to Form Tumors (2015) | Plants and Microbes | Scoop.it

The biotrophic smut fungus Ustilago maydis infects all aerial organs of maize (Zea mays) and induces tumors in the plant tissues. U. maydis deploys many effector proteins to manipulate its host. Previously, deletion analysis demonstrated that several effectors have important functions in inducing tumor expansion specifically in maize leaves. Here, we present the functional characterization of the effector See1 (Seedling efficient effector1). See1 is required for the reactivation of plant DNA synthesis, which is crucial for tumor progression in leaf cells. By contrast, See1 does not affect tumor formation in immature tassel floral tissues, where maize cell proliferation occurs independent of fungal infection. See1 interacts with a maize homolog of SGT1 (Suppressor of G2 allele of skp1), a factor acting in cell cycle progression in yeast (Saccharomyces cerevisiae) and an important component of plant and human innate immunity. See1 interferes with the MAPK-triggered phosphorylation of maize SGT1 at a monocot-specific phosphorylation site. We propose that See1 interferes with SGT1 activity, resulting in both modulation of immune responses and reactivation of DNA synthesis in leaf cells. This identifies See1 as a fungal effector that directly and specifically contributes to the formation of leaf tumors in maize.

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4th International Conference on Biotic Plant Interactions, Nanjing, Jiangsu, China, Aug 1-3, 2015.

4th International Conference on Biotic Plant Interactions, Nanjing, Jiangsu, China, Aug 1-3, 2015. | Plants and Microbes | Scoop.it

Plants constantly interact with a wide range of microbes and insects. These interactions, which can be beneficial or harmful to plants, influence greatly on agricultural production and our daily life. On behalf of the steering committee, it is our pleasure to invite colleagues in the fields of biotic plant interactions to attend the 4th International Conference on Biotic Plant Interactions, which will be held at Nanjing, Jiangsu, China, on Aug 1-3, 2015.


The theme of this 3-day meeting is Biotic Plant Interactions and Agricultural Production. As a continuing effort after the 1st conference held in Brisbane, Australia, 2008, 2nd conference held in Kunming, China, 2011, and 3rd conference held in Yangling, China, 2013, this meeting will cover a wide range of scientific research topics spanning Plant Pathology, Plant-Microbe Interactions, Plant-Insect interactions, Pathogen and Insect Genomics and Molecular Evolution, and Biotechnology on disease and insect resistance. This conference will bring together scientists and students who are interested in plant pathology and beneficial interactions of plants with other organisms, including viruses, bacteria, fungi, oomycetes, nematodes, insects and other herbivores, and genomics and evolution of pathogens and insects.


We are looking forward to welcoming you in Nanjing, China.


Sincerely Yours!


Yuanchao Wang & Zuhua He


Chairmans of the Organizing Committee

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eLife: Natural genetic variation in Arabidopsis thaliana defense metabolism genes modulates field fitness (2015)

eLife: Natural genetic variation in Arabidopsis thaliana defense metabolism genes modulates field fitness (2015) | Plants and Microbes | Scoop.it

Natural populations persist in complex environments, where biotic stressors, such as pathogen and insect communities, fluctuate temporally and spatially. These shifting biotic pressures generate heterogeneous selective forces that can maintain standing natural variation within a species. To directly test if genes containing causal variation for the Arabidopsis thaliana defensive compounds, glucosinolates (GSL) control field fitness and are therefore subject to natural selection, we conducted a multi-year field trial using lines that vary in only specific causal genes. Interestingly, we found that variation in these naturally polymorphic GSL genes affected fitness in each of our environments but the pattern fluctuated such that highly fit genotypes in one trial displayed lower fitness in another and that no GSL genotype or genotypes consistently out-performed the others. This was true both across locations and within the same location across years. These results indicate that environmental heterogeneity may contribute to the maintenance of GSL variation observed within Arabidopsis thaliana.

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The Conversation: The cutting-edge science taking on some of the world's most notorious parasitic plants (2015)

The Conversation: The cutting-edge science taking on some of the world's most notorious parasitic plants (2015) | Plants and Microbes | Scoop.it
Little is known about how parasitic plants live side-by-side with their hosts. But new genetic techniques may help scientists gain further insights.


Thousands of plant species have adopted a “parasitic” mode of life, living off a host plant which supplies it with water and nutrients. Most of these remain harmless, but a few have evolved to become serious agricultural weeds that threaten food security in some of the world’s poorest regions.

Parasitic plants are deceptively common, you have probably come across the snarling strands of Dodder – a stem parasite which infects nettles – in a local hedgerow. Even the world’s largest flower, Rafflesia arnoldii, found in the rainforests of South-East Asia, is a parasite, infecting and living off tropical vines.

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ASPB News: 2015 Charles Albert Shull Award Winner: Dr. Cyril Zipfel

ASPB News: 2015 Charles Albert Shull Award Winner: Dr. Cyril Zipfel | Plants and Microbes | Scoop.it

Cyril Zipfel, who heads The Sainsbury Laboratory, is the 2015 recipient of the Charles Albert Shull Award. Cyril played a leading role in the discovery of pattern-triggered immunity in plants, including the characterization of the bacterial peptides flagellin (flg22) and EF-Tu (elf18) as pattern-associated molecular markers that activate signaling by the receptor-like kinases FLS2 and EFR, respectively, leading to plant immunity. He found that the brassinosteroid co-receptor, BAK1, also cooperates with 2 FLS2 and EFR, and he identified residues of BAK1 that are key to specifying co-receptor output toward brassinosteroid signaling, cell death control, or innate immunity. Cyril also made the major practical discovery that transgenic expression of Arabidopsis EFR in Solanaceous species, which normally do not recognize the bacterial ligand EF-Tu, confers immunity to a broad range of bacteria, and he has extended this approach to cereals. Honors will be presented at the Plant Biology 2015 meeting in Minneapolis. You can read the full list of 2015 ASPB awardees on the ASPB website.

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Euro J. Biochem: Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco (1989)

Euro J. Biochem: Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco (1989) | Plants and Microbes | Scoop.it

The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non-host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianae, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 μg/plant, whereas 50-fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10323 and 10155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C-terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.

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#JGI2015 Day 3 of 10th Annual DOE Joint Genome Institute Genomics of Energy & Environment Meeting (with images, tweets)

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PLOS ONE: Novel Mutations Detected in Avirulence Genes Overcoming Tomato Cf Resistance Genes in Isolates of a Japanese Population of Cladosporium fulvum (2015)

PLOS ONE: Novel Mutations Detected in Avirulence Genes Overcoming Tomato  Cf  Resistance Genes in Isolates of a Japanese Population of  Cladosporium fulvum (2015) | Plants and Microbes | Scoop.it

Leaf mold of tomato is caused by the biotrophic fungus Cladosporium fulvum which complies with the gene-for-gene system. The disease was first reported in Japan in the 1920s and has since been frequently observed. Initially only race 0 isolates were reported, but since the consecutive introduction of resistance genes Cf-2Cf-4Cf-5 and Cf-9 new races have evolved. Here we first determined the virulence spectrum of 133 Cfulvum isolates collected from 22 prefectures in Japan, and subsequently sequenced the avirulence (Avr) genes Avr2Avr4Avr4EAvr5 and Avr9 to determine the molecular basis of overcoming Cf genes. Twelve races of Cfulvum with a different virulence spectrum were identified, of which races 9, 2.9, 4.9, 4.5.9 and 4.9.11 occur only in Japan. The Avr genes in many of these races contain unique mutations not observed in races identified elsewhere in the world including (i) frameshift mutations and (ii) transposon insertions in Avr2, (iii) point mutations in Avr4 and Avr4E, and (iv) deletions of Avr4EAvr5 and Avr9. New races have developed by selection pressure imposed by consecutive introductions of Cf-2Cf-4Cf-5 and Cf-9 genes in commercially grown tomato cultivars. Our study shows that molecular variations to adapt to different Cf genes in an isolated Cfulvum population in Japan are novel but overall follow similar patterns as those observed in populations from other parts of the world. Implications for breeding of more durable Cfulvumresistant varieties are discussed.

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Fungal Genetics & Biology: The ipiO Gene of Phytophthora infestans Is Highly Expressed in Invading Hyphae during Infection (1998)

Fungal Genetics & Biology: The ipiO Gene of Phytophthora infestans Is Highly Expressed in Invading Hyphae during Infection (1998) | Plants and Microbes | Scoop.it

The expression of thein planta-induced geneipiO of the potato late blight pathogenPhytophthora infestanswas analyzed during various developmental stages of its life cycle.ipiO mRNA was detected in zoospores, cysts, germinating cysts, and young mycelia, but not in sporangia or in old mycelia grownin vitro. ipiO is not only expressed in stages prior to infection but also during colonization of potato and tomato leaves. In disease lesions,ipiO mRNA was detected in the water-soaked area and the healthy-looking plant tissue surrounding it. In contrast,ipiO mRNA was not found in necrotized tissue or in sporulating areas of a lesion. To determine more precisely the location and time ofipiO gene expressionin planta,cytological assays were performed using aP. infestanstransformant expressing a transcriptional fusion between theipiO1 promoter and the β-glucuronidase (GUS) reporter gene. GUS staining was found specifically in the subapical and vacuolated area of tips of invading hyphae. The histochemical GUS assays demonstrate thatipiO is expressed during biotrophic stages of the disease cycle.

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Wheat diseases: a threat to the greatest crop on earth, 22 May 2015, The Sainsbury Laboratory, Norwich, United Kingdom

Wheat diseases: a threat to the greatest crop on earth, 22 May 2015, The Sainsbury Laboratory, Norwich, United Kingdom | Plants and Microbes | Scoop.it

You are invited to attend a special day on wheat disease resistance at the John Innes Conference Centre on Friday 22 May 2015 in Norwich.


This day will bring together scientists, plant breeders, growers and policy-makers in a series of scientific seminars and networking. The day’s sessions will highlight current research and strategies for delivering increased and sustainable production of wheat in face of the many diseases that infect this crop.


Wheat is the most widely planted crop in the world and has an average production of 650 million tonnes per year, of which 65% is for human consumption. An increasing world population has placed substantial demands on wheat production, a battle exacerbated by the many and emerging diseases which can compromise crop quality and yield.


World-leading scientists from the John Innes Centre, The Genome Analysis Centre (TGAC), and The Sainsbury Laboratory (TSL) are carrying out strategic research into the biology and evolution of wheat diseases, as well as in the genomics and immune responses of wheat. These programmes, which further highlight the integrative and collaborative nature of research across these different institutes on the Norwich Research Park, are required to provide practical solutions to the significant challenge caused by wheat diseases in UK and worldwide.


Programme


9:30 Registration and refreshments
10:00 Introduction by John Snape (JIC)
10:10 Dr. Ravi Singh (CIMMYT): Approaches to develop and deliver high yielding, disease resistant wheat germplasm at CIMMYT
10:50 Introduction to the Norwich Rust Group
11:00 Dr. Cristobal Uauy (JIC)
11:25 Refreshments
11:50 Dr. Diane Saunders (TGAC/JIC)
12:15 Prof. James Brown (JIC)
12:40 Lunch
13:40 Dr. Kim Hammond-Kosack (Rothamsted)
14:20 Dr. Brande Wulff (JIC)
14:45 Dr. Matthew Moscou (TSL)
15:10 Refreshments
15:35 Dr. Paul Nicholson (JIC)
16:00 Dr. Ksenia Krasileva (TGAC/TSL)
16:25 Concluding remarks by John Snape (JIC)
16:30 Closing remarks

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Molecular Plant Pathology: A new look at plant viruses and their potential beneficial roles in crops (2015)

Molecular Plant Pathology: A new look at plant viruses and their potential beneficial roles in crops (2015) | Plants and Microbes | Scoop.it

Twenty years ago most people (including many scientists) thought of bacteria solely as agents of disease, best treated with disinfectants and antibiotics. Today, most of us are aware that bacteria make up almost 90% of the cells in our bodies, and play a critical role in digestion and the immune response. In plants, bacteria also form important mutualistic relationships, providing nitrogen fixation, growth enhancement and defence against pathogens, and undoubtedly a host of other functions that have yet to be described. The stigma of bacteria has changed dramatically in recent decades, and most people are aware that we need our good microbes.


Although there have been recent efforts to characterize the plant microbiome with a focus on finding beneficial microbes, viruses generally have not been included in the beneficial microbe lists (Berg et al., 2014, and references cited therein). Recent work has indicated that they can also play important and beneficial roles in plants, especially in extreme environments in which they are involved in conferring tolerance to drought, cold and hot soil temperatures (Roossinck, 2011). Beneficial viruses are defined for the purposes of this discussion as viruses that provide a trait to crop plants that increases their value or growth potential, or decreases the need for the use of chemical fertilizers or pesticides.


See also http://www.noble.org/ag/research/microbes/

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PNAS: The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop (2015)

PNAS: The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop (2015) | Plants and Microbes | Scoop.it

Agrobacterium rhizogenes and Agrobacterium tumefaciens are plant pathogenic bacteria capable of transferring DNA fragments [transfer DNA (T-DNA)] bearing functional genes into the host plant genome. This naturally occurring mechanism has been adapted by plant biotechnologists to develop genetically modified crops that today are grown on more than 10% of the world’s arable land, although their use can result in considerable controversy. While assembling small interfering RNAs, or siRNAs, of sweet potato plants for metagenomic analysis, sequences homologous to T-DNA sequences from Agrobacterium spp. were discovered. Simple and quantitative PCR, Southern blotting, genome walking, and bacterial artificial chromosome library screening and sequencing unambiguously demonstrated that two different T-DNA regions (IbT-DNA1 and IbT-DNA2) are present in the cultivated sweet potato (Ipomoea batatas [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. IbT-DNA1 was found to contain four open reading frames (ORFs) homologous to the tryptophan-2-monooxygenase (iaaM), indole-3-acetamide hydrolase (iaaH), C-protein (C-prot), and agrocinopine synthase (Acs) genes of Agrobacterium spp. IbT-DNA1 was detected in all 291 cultigens examined, but not in close wild relatives. IbT-DNA2 contained at least five ORFs with significant homology to the ORF14, ORF17n, rooting locus (Rol)B/RolC, ORF13, and ORF18/ORF17n genes of A. rhizogenes. IbT-DNA2 was detected in 45 of 217 genotypes that included both cultivated and wild species. Our finding, that sweet potato is naturally transgenic while being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops.

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PNAS: Phytophthora effector targets a novel component of small RNA pathway in plants to promote infection (2015)

PNAS: Phytophthora effector targets a novel component of small RNA pathway in plants to promote infection (2015) | Plants and Microbes | Scoop.it

Phytophthora is a major threat to agriculture. However, the molecular interaction of these severe pathogens with plant hosts is poorly understood. Here, we report that the Phytophthora Suppressor of RNA Silencing 1 (PSR1) effectively promotes infection in Arabidopsis thaliana by directly targeting an essential protein containing a aspartate–glutamate–alanine–histidine-box RNA helicase domain. This PSR1-Interacting Protein 1 (PINP1) is required for the accumulation of distinct classes of endogenous small RNAs and acts as a positive regulator of plant immunity. Silencing of PINP1 impaired the assembly of microRNA-processing complexes in the nucleus, leading to defects in development and immunity. This study revealed a conserved RNA helicase as a regulator of RNA silencing and provides mechanistic insight into Phytophthora pathogenesis.

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The New Yorker: We Have No Bananas - Can scientists defeat a devastating blight? (2015)

The New Yorker: We Have No Bananas - Can scientists defeat a devastating blight? (2015) | Plants and Microbes | Scoop.it

Darwin, the capital of Australia’s Northern Territory, is more than a thousand miles northwest of the country’s largest banana plantations, which are centered around Innisfail, on the eastern seaboard. A ramshackle place, Darwin is known for its many impoverished indigenous residents, entertainment attractions like Crocosaurus Cove (where visitors are lowered, via “the Cage of Death,” into a crocodile-filled tank), and, as one local puts it, “not partying, exactly, but certainly drinking.” To Robert Borsato, a fruit farmer, the area looked like an ideal place to grow bananas. In 1996, he began farming a thousand acres in Humpty Doo, which is on the road between Darwin and Kakadu National Park.


To bear fruit, banana plants need at least fourteen consecutive months of frost-free weather, which is why they are not grown commercially in the continental United States. Darwin offered this, and more. As one of Borsato’s workers told me recently, “You came up here and saw the consistency that you’ve got between the blue sky, the sunshine, the water, the fucking soil. You knew you were going to beat everybody else, hands down.” There were a few nuisances: crocodiles wandered onto the property, Asian buffalo trampled young plants, and dingoes chewed the sprinklers. Before long, though, the Darwin Banana Farming Company was growing lush ten-foot plants with as many as a hundred and seventy bananas on each stalk. In 2006, Cyclone Larry decimated ninety per cent of the Innisfail plantations; banana prices soared from ten dollars a carton to a hundred and thirty, and Borsato became a multimillionaire.


More than a thousand kinds of banana can be found worldwide, but Borsato specialized in a variety called Cavendish, which a nineteenth-century British explorer happened upon in a household garden in southern China. Today, the Cavendish represents ninety-nine per cent of the banana export market. The vast majority of banana varieties are not viable for international trade: their bunches are too small, or their skin is too thin, or their pulp is too bland. Although Cavendishes need pampering, they are the only variety that provides farmers with a high yield of palatable fruit that can endure overseas trips without ripening too quickly or bruising too easily. The Cavendish, which is rich in Vitamins B6 and C, has high levels of potassium, magnesium, and fibre; it is also cheap—about sixty cents a pound. In 2008, Americans ate 7.6 billion pounds of Cavendish bananas, virtually all of them imported from Latin America. Each year, we eat as many Cavendish bananas as we do apples and oranges combined. Your supermarket likely sells many varieties of apples, but when you shop for bananas you usually have one option. The world’s banana plantations are a monoculture of Cavendishes.


Several years ago, Borsato noticed a couple of sick-looking plants on a neighbor’s property. The leaves turned a soiled yellow, starting at the edges and rapidly moving inward; necrotic patches appeared and, a few weeks later, the leaves buckled. What had once formed a canopy now dangled around the base of the plant, like a cast-off grass skirt. Inside the plant, the effects were even worse. Something was blocking the plants’ vascular system, causing rot, and tissue that should have been as ivory as the inside of a celery stalk was a putrefying mixture of brown, black, and blood-red. When the plants were cut open, they smelled like garbage, and their roots were so anemic that the plants could barely stay upright.


Borsato feared that he was seeing the symptoms of a pestilence that had wiped out the Cavendish across Asia: Tropical Race Four. A soil-borne fungus that is known to be harmful only to bananas, it can survive for decades in the dirt, spreading through the transportation of tainted plants, or in infected mud stuck to a tractor’s tire or a rancher’s boot. It cannot be controlled with chemicals. Tropical Race Four appeared in Taiwan in the late eighties, and destroyed roughly seventy per cent of the island’s Cavendish plantations. In Indonesia, more than twelve thousand acres of export bananas were abandoned; in Malaysia, a local newspaper branded the disease “the H.I.V. of banana plantations.” When the fungus reached China and the Philippines, the effect was equally ruinous.


[Fusarium oxysporum f. sp. cubense TR4]

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New Phytologist: The tomato I-3 gene: a novel gene for resistance to Fusarium wilt disease - Catanzariti (2015)

New Phytologist: The tomato I-3 gene: a novel gene for resistance to Fusarium wilt disease - Catanzariti (2015) | Plants and Microbes | Scoop.it
  • Plant resistance proteins provide race-specific immunity through the recognition of pathogen effectors. The resistance genes I, I-2 and I-3 have been incorporated into cultivated tomato (Solanum lycopersicum) from wild tomato species to confer resistance against Fusarium oxysporum f. sp. lycopersici (Fol) races 1, 2 and 3, respectively. Although the Fol effectors corresponding to these resistance genes have all been identified, only the I-2 resistance gene has been isolated from tomato.
  • To isolate the I-3 resistance gene, we employed a map-based cloning approach and used transgenic complementation to test candidate genes for resistance to Fol race 3.
  • Here, we describe the fine mapping and sequencing of genes at the I-3 locus, which revealed a family of S-receptor-like kinase (SRLK) genes. Transgenic tomato lines were generated with three of these SRLK genes and one was found to confer Avr3-dependent resistance to Fol race 3, confirming it to be I-3.
  • The finding that I-3 encodes an SRLK reveals a new pathway for Fol resistance and a new class of resistance genes, of which Pi-d2from rice is also a member. The identification of I-3 also allows the investigation of the complex effector–resistance protein interaction involving Avr1-mediated suppression of I-2- and I-3-dependent resistance in tomato.
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New Phytologist: Tissue-specific FLAGELLIN-SENSING 2 (FLS2) expression in roots restores immune responses in Arabidopsis fls2 mutants (2015)

New Phytologist: Tissue-specific FLAGELLIN-SENSING 2 (FLS2) expression in roots restores immune responses in Arabidopsis fls2 mutants (2015) | Plants and Microbes | Scoop.it
  • The flagellin receptor of Arabidopsis, At-FLAGELLIN SENSING 2 (FLS2), has become a model for mechanistic and functional studies on plant immune receptors. Responses to flagellin or its active epitope flagellin 22 (flg22) have been extensively studied in Arabidopsis leaves. However, the perception of microbe-associated molecular patterns (MAMPs) and the immune responses in roots are poorly understood.
  • Here, we show that isolated root tissue is able to induce pattern-triggered immunity (PTI) responses upon flg22 perception, in contrast to elf18 (the active epitope of elongation factor thermo unstable (EF-Tu)). Making use of fls2 mutant plants and tissue-specific promoters, we generated transgenic Arabidopsis lines expressing FLS2 only in certain root tissues. This allowed us to study the spatial requirements for flg22 responses in the root.
  • Remarkably, the intensity of the immune responses did not always correlate with the expression level of the FLS2 receptor, but depended on the expressing tissue, supporting the idea that MAMP perception and sensitivity in different tissues contribute to a proper balance of defense responses according to the expected exposure to elicitors.
  • In summary, we conclude that each investigated root tissue is able to perceive flg22 if FLS2 is present and that tissue identity is a major element of MAMP perception in roots.
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ASPB News: 2015 Dennis R. Hoagland Award Winner: Dr. Maria Harrison

ASPB News: 2015 Dennis R. Hoagland Award Winner: Dr. Maria Harrison | Plants and Microbes | Scoop.it

Dr. Maria Harrison, Boyce Thompson Institute for Plant Science, has pioneered studies of phosphate acquisition in arbuscular mycorrhizal (AM) symbioses using the model legume Medicago truncatula. In particular, her findings that phosphate transport is linked to maintenance of symbiosis and that plants use classic hormone signaling pathways for regulation of the AM symbiosis have ushered the field of fungal–plant interactions in new directions, and they provide opportunities for the future manipulation of phosphate acquisition in crop species. Maria has identified key gene products required for phosphate transport and uptake, and she has shown that redirected plant protein secretion mechanisms target transporters to symbiotic membranes. Maria has also has developed cell biology resources for in vivo cellular imaging in Medicago that expand research capabilities to further unravel the nutritional function of the AM symbiosis. The Hoagland award is given in recognition of her outstanding contributions to plant mineral nutrition. Honors will be presented at the Plant Biology 2015 meeting in Minneapolis. You can read the full list of 2015 ASPB awardees on the ASPB website.


Via Jean-Michel Ané, Pierre-Marc Delaux
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New Phytologist: Immune activation mediated by the late blight resistance protein R1 requires nuclear localization of R1 and the effector AVR1 (2015)

New Phytologist: Immune activation mediated by the late blight resistance protein R1 requires nuclear localization of R1 and the effector AVR1 (2015) | Plants and Microbes | Scoop.it
  • Resistance against oomycete pathogens is mainly governed by intracellular nucleotide-binding leucine-rich repeat (NLR) receptors that recognize matching avirulence (AVR) proteins from the pathogen, RXLR effectors that are delivered inside host cells. Detailed molecular understanding of how and where NLR proteins and RXLR effectors interact is essential to inform the deployment of durable resistance (R) genes.
  • Fluorescent tags, nuclear localization signals (NLSs) and nuclear export signals (NESs) were exploited to determine the subcellular localization of the potato late blight protein R1 and the Phytophthora infestans RXLR effector AVR1, and to target these proteins to the nucleus or cytoplasm.
  • Microscopic imaging revealed that both R1 and AVR1 occurred in the nucleus and cytoplasm, and were in close proximity. Transient expression of NLS- or NES-tagged R1 and AVR1 in Nicotiana benthamiana showed that activation of the R1-mediated hypersensitive response and resistance required localization of the R1/AVR1 pair in the nucleus. However, AVR1-mediated suppression of cell death in the absence of R1 was dependent on localization of AVR1 in the cytoplasm. Balanced nucleocytoplasmic partitioning of AVR1 seems to be a prerequisite.
  • Our results show that R1-mediated immunity is activated inside the nucleus with AVR1 in close proximity and suggest that nucleocytoplasmic transport of R1 and AVR1 is tightly regulated.
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Nature Plants: Elicitin recognition confers enhanced resistance to Phytophthora infestans in potato (2015)

Nature Plants: Elicitin recognition confers enhanced resistance to Phytophthora infestans in potato (2015) | Plants and Microbes | Scoop.it

Potato late blight, caused by the destructive Irish famine pathogen Phytophthora infestans, is a major threat to global food security1,2. All late blight resistance genes identified to date belong to the coiled-coil, nucleotide-binding, leucine-rich repeat class of intracellular immune receptors3. However, virulent races of the pathogen quickly evolved to evade recognition by these cytoplasmic immune receptors4. Here we demonstrate that the receptor-like protein ELR (elicitin response) from the wild potato Solanum microdontum mediates extracellular recognition of the elicitin domain, a molecular pattern that is conserved in Phytophthora species. ELR associates with the immune co-receptor BAK1/SERK3 and mediates broad-spectrum recognition of elicitin proteins from several Phytophthora species, including four diverse elicitins from P. infestans. Transfer of ELR into cultivated potato resulted in enhanced resistance to P. infestans. Pyramiding cell surface pattern recognition receptors with intracellular immune receptors could maximize the potential of generating a broader and potentially more durable resistance to this devastating plant pathogen.

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