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Rescooped by James Hane from TAL effector science
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XA23 is an executor R protein and confers broad-spectrum disease resistance in rice - Mol. Plant

XA23 is an executor R protein and confers broad-spectrum disease resistance in rice - Mol. Plant | plant pathogen interactions | Scoop.it

(via T. Schreiber, thx)

Wang et al, 2014

The majority of plant disease resistance (R) genes encode proteins that share common structural features. However, the transcription activator-like effector (TALE) associated executor type R genes show no considerable sequence homology to any known R genes. We adopted a map-based cloning approach and TALE-based technology to isolate and characterize Xa23, a new executor R gene derived from the wild rice (Oryza rufipogon) that confers an extremely broad spectrum of resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). Xa23 encodes a 113-amino acid protein that shares 50% identity to the known executor R protein XA10. The predicted transmembrane helices in XA23 also overlap with those of XA10. Unlike Xa10, however, Xa23 transcription is specifically activated by AvrXa23, a TALE present in all examined Xoo field isolates. Moreover, the susceptible xa23 allele has an identical open reading frame of Xa23, but differs in promoter region by lacking the TALE binding-element (EBE) for AvrXa23. XA23 can trigger strong hypersensitive response in rice, tobacco and tomato. Our results provide the first evidence that plant genomes have an executor R gene family in which members execute their function and spectrum of disease resistance by recognizing the cognate TALEs in pathogen.


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The Scientist: Opinion: The Planet Needs More Plant Scientists (2014)

The Scientist: Opinion: The Planet Needs More Plant Scientists (2014) | plant pathogen interactions | Scoop.it

Academia is not producing sufficient PhDs in the plant sciences to solve the crop production challenges facing a rapidly growing population.


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Peter Buckland's curator insight, October 2, 6:34 AM

Yet more evidence of the decline in plant sciences

Rescooped by James Hane from Virology and Bioinformatics from Virology.ca
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SDT: A Virus Classification Tool Based on Pairwise ... [PLoS One. 2014] - PubMed - NCBI

SDT: A Virus Classification Tool Based on Pairwise ... [PLoS One. 2014] - PubMed - NCBI | plant pathogen interactions | Scoop.it

The perpetually increasing rate at which viral full-genome sequences are being determined is creating a pressing demand for computational tools that will aid the objective classification of these genome sequences. Taxonomic classification approaches that are based on pairwise genetic identity measures are potentially highly automatable and are progressively gaining favour with the International Committee on Taxonomy of Viruses (ICTV). There are, however, various issues with the calculation of such measures that could potentially undermine the accuracy and consistency with which they can be applied to virus classification.  


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Aphid gene of bacterial origin encodes a protein transported to an obligate endosymbiont

Aphid gene of bacterial origin encodes a protein transported to an obligate endosymbiont | plant pathogen interactions | Scoop.it

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Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014)

Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014) | plant pathogen interactions | Scoop.it

Neurospora crassa has a long history as an excellent model for genetic, cellular, and biochemical research. Although this fungus is known as a saprotroph, it normally appears on burned vegetations or trees after forest fires. However, due to a lack of experimental evidence, the nature of its association with living plants remains enigmatic. Here we report that Scots pine (Pinus sylvestris) is a host plant for N. crassa. The endophytic lifestyle of N. crassa was found in its interaction with Scots pine. Moreover, the fungus can switch to a pathogenic state when its balanced interaction with the host is disrupted. Our data reveal previously unknown lifestyles of N. crassa, which are likely controlled by both environmental and host factors. Switching among the endophytic, pathogenic, and saprotrophic lifestyles confers upon fungi phenotypic plasticity in adapting to changing environments and drives the evolution of fungi and associated plants.


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MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014)

MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014) | plant pathogen interactions | Scoop.it

Vascular wilts caused by Verticillium spp. are destructive plant diseases, affecting hundreds of hosts. Only few Verticillium spp. are causal agents of vascular wilt diseases, of which V. dahliae is the most notorious pathogen, and several V. dahliae genomes are available. In contrast, V. tricorpus is mainly known as saprophyte and causal agent of opportunistic infections. Based on a hybrid approach that combines second and third generation sequencing, a near-gapless V. tricorpus genome assembly was obtained. With comparative genomics, we aimed to identify genomic features in V. dahliae that confer the ability to cause vascular wilt disease. Unexpectedly, both species encode similar effector repertoires and share a genomic structure with genes encoding secreted proteins clustered in genomic islands. Intriguingly, V. tricorpus contains significantly less repetitive elements and an extended spectrum of secreted carbohydrate-active enzymes when compared with V. dahliae. In conclusion, we highlight the technical advances of a hybrid sequencing and assembly approach and reveal that the saprophyte V. tricorpus shares many hallmark features with V. dahliae.


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PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014)

PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014) | plant pathogen interactions | Scoop.it

Rust diseases caused by fungi of the order Pucciniales afflict a wide range of plants, including cereals, legumes, ornamentals, and fruit trees, and pose a serious threat to cropping systems and global food security. The obligate parasitic lifestyle of these fungi and their complex life cycles, often involving alternate hosts for the sexual and asexual stages, also make this group of pathogens of great biological interest. One of the most remarkable adaptations of rust fungi is the specialized infection structure that underpins the sustained biotrophic association with hosts; the haustorium (Figure 1A and C). This organ forms after penetration of the wall of a live host cell, expanding on the inner side of the cell wall while invaginating the surrounding host plasma membrane (Figure 1C). Through haustoria, the pathogen derives nutrients from the host and secretes virulence proteins called effectors, which are believed to be the key players that manipulate the physiological and immune responses of host cells [1]–[4]. Analogous terminal feeding structures have independently evolved in other organisms such as the haustorium in powdery mildews (ascomycetes) and downy mildews (oomycetes, not true fungi), and the arbuscules in arbuscular mycorrhizae, suggesting that such architecture represents a successful adaptation of these organisms to interact with their respective host plants [5], [6].


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Global Ecology and Biogeography: The global spread of crop pests and pathogens (2014)

Global Ecology and Biogeography: The global spread of crop pests and pathogens (2014) | plant pathogen interactions | Scoop.it

Aim - To describe the patterns and trends in the spread of crop pests and pathogens around the world, and determine the socioeconomic, environmental and biological factors underlying the rate and degree of redistribution of crop-destroying organisms.


Location - Global.


Methods - Current country- and state-level distributions of 1901 pests and pathogens and historical observation dates for 424 species were compared with potential distributions based upon distributions of host crops. The degree of ‘saturation’, i.e. the fraction of the potential distribution occupied, was related to pest type, host range, crop production, climate and socioeconomic variables using linear models.


Results - More than one-tenth of all pests have reached more than half the countries that grow their hosts. If current trends continue, many important crop-producing countries will be fully saturated with pests by the middle of the century. While dispersal increases with host range overall, fungi have the narrowest host range but are the most widely dispersed group. The global dispersal of some pests has been rapid, but pest assemblages remain strongly regionalized and follow the distributions of their hosts. Pest assemblages are significantly correlated with socioeconomics, climate and latitude. Tropical staple crops, with restricted latitudinal ranges, tend to be more saturated with pests and pathogens than temperate staples with broad latitudinal ranges. We list the pests likely to be the most invasive in coming years.


Main conclusions - Despite ongoing dispersal of crop pests and pathogens, the degree of biotic homogenization of the globe remains moderate and regionally constrained, but is growing. Fungal pathogens lead the global invasion of agriculture, despite their more restricted host range. Climate change is likely to influence future distributions. Improved surveillance would reveal greater levels of invasion, particularly in developing countries.


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Nature Communications: Unconventionally secreted effectors of two filamentous pathogens target plant salicylate biosynthesis (2014)

Nature Communications: Unconventionally secreted effectors of two filamentous pathogens target plant salicylate biosynthesis (2014) | plant pathogen interactions | Scoop.it

Plant diseases caused by fungi and oomycetes pose an increasing threat to food security and ecosystem health worldwide. These filamentous pathogens, while taxonomically distinct, modulate host defense responses by secreting effectors, which are typically identified based on the presence of signal peptides. Here we show that Phytophthora sojae and Verticillium dahliaesecrete isochorismatases (PsIsc1 and VdIsc1, respectively) that are required for full pathogenesis. PsIsc1 and VdIsc1 can suppress salicylate-mediated innate immunity in plantaand hydrolyse isochorismate in vitro. A conserved triad of catalytic residues is essential for both functions. Thus, the two proteins are isochorismatase effectors that disrupt the plant salicylate metabolism pathway by suppressing its precursor. Furthermore, these proteins lack signal peptides, but exhibit characteristics that lead to unconventional secretion. Therefore, this secretion pathway is a novel mechanism for delivering effectors and might play an important role in host–pathogen interactions.


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Rescooped by James Hane from Genomics and metagenomics of microbes
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BMC Genomics | Full text | HGTector: an automated method facilitating genome-wide discovery of putative horizontal gene transfers

BMC Genomics | Full text | HGTector: an automated method facilitating genome-wide discovery of putative horizontal gene transfers | plant pathogen interactions | Scoop.it
First pass methods based on BLAST match are commonly used as an initial step to separate the different phylogenetic histories of genes in microbial genomes, and target putative horizontal gene transfer (HGT) events. This will continue to be necessary given the rapid growth of genomic data and the technical difficulties in conducting large-scale explicit phylogenetic analyses. However, these methods often produce misleading results due to their inability to resolve indirect phylogenetic links and their vulnerability to stochastic events.

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MPMI: Comparative and functional analysis of the widely occurring family of Nep1-like proteins (2014)

MPMI: Comparative and functional analysis of the widely occurring family of Nep1-like proteins (2014) | plant pathogen interactions | Scoop.it

Nep-1 Like Proteins (NLPs) are best known for their cytotoxic activity in dicot plants. NLPs are taxonomically widespread among microbes with very different lifestyles. To learn more about this enigmatic protein family we analyzed more than 500 available NLP protein sequences from fungi, oomycetes, and bacteria. Phylogenetic clustering showed that, besides the previously documented two types, an additional more divergent third NLP type could be distinguished. By closely examining the three NLP types, we identified a non-cytotoxic subgroup of type 1 NLPs (designated type 1a), which have substitutions in amino acids making up a cation-binding pocket that is required for cytotoxicity. Type 2 NLPs were found to contain a putative calcium-binding motif, which was shown to be required for cytotoxicity. Members of both type 1 and type 2 NLPs were found to possess additional cysteine residues that, based on their predicted proximity, make up potential disulfide bridges that could provide additional stability to these secreted proteins. Type 1 and type 2 NLPs, although both cytotoxic to plant cells, differ in their ability to induce necrosis when artificially targeted to different cellular compartments in planta, suggesting they have different mechanisms of cytotoxicity.


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Nature Biotechnology: Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew (2014)

Nature Biotechnology: Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew (2014) | plant pathogen interactions | Scoop.it

Sequence-specific nucleases have been applied toengineer targeted modifications in polyploid genomes, but simultaneous modification of multiple homoeoalleles has not been reported. Here we use transcription activator–like effector nuclease (TALEN) and clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 technologies in hexaploid bread wheat to introduce targeted mutations in the three homoeoalleles that encode MILDEW- RESISTANCE LOCUS (MLO) proteins. Genetic redundancy has prevented evaluation of whether mutation of all three MLO alleles in bread wheat might confer resistance to powdery mildew, a trait not found in natural populations. We show that TALEN-induced mutation of all three TaMLO homoeologs in the same plant confers heritable broad-spectrum resistanceto powdery mildew. We further use CRISPR-Cas9 technologyto generate transgenic wheat plants that carry mutations inthe TaMLO-A1 allele. We also demonstrate the feasibility of engineering targeted DNA insertion in bread wheat through nonhomologous end joining of the double-strand breaks caused by TALENs. Our findings provide a methodological framework to improve polyploid crops.

 


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Fesquet didier's curator insight, July 22, 5:22 AM

this open the way for developping non toxic wheat species...good for celiac people...maybe one day...hopes for a slice of pizza :-)

 

Mary Williams's curator insight, July 31, 6:33 AM

I'm trying to catch up with what I missed while traveling. I think this is one of the more exciting papers that came out in the past few weeks, and I'm a bit surprised that it didn't get more press coverage.

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Mashable: Chinese Researchers Create Disease-Resistant Wheat by Deleting Genes (2014)

Mashable: Chinese Researchers Create Disease-Resistant Wheat by Deleting Genes (2014) | plant pathogen interactions | Scoop.it

Advanced genome-editing techniques have been used to create a strain of wheat resistant to a destructive fungal pathogen — called powdery mildew — that is a major bane to the world's top food source, according to scientists at one of China's leading centers for agricultural research.

 

To stop the mildew, researchers at the Chinese Academy of Sciences deleted genes that encode proteins that repress defenses against the mildew. The work promises to someday make wheat more resistant to the disease, which is typically controlled through the heavy use of fungicides. It also represents an important achievement in using genome editing tools to engineer food crops without inserting foreign genes — a flashpoint for opposition to genetically modified crops.

 

The gene-deletion trick is particularly tough to do in wheat because the plant has three genomes — with largely similar copies of the same genes — meaning all three must be deleted or the trait will not be changed. Using gene-editing tools known as TALENs and CRISPR, the researchers were able to do that without changing anything else or adding genes from other organisms.

 

"We now caught all three copies, and only by knocking out all three copies can we get this [mildew]-resistant phenotype," says Caixia Gao, who heads a gene-editing research group at the State Key Laboratory of Plant Cell and Chromosome Engineering at the Institute of Microbiology in Beijing.

 

A paper describing the results appears in Nature Biotechnology http://dx.doi.org/10.1038/nbt.2969.


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Long-distance endosome trafficking drives fungal effector production during plant infection : Nature Communications : Nature Publishing Group

Long-distance endosome trafficking drives fungal effector production during plant infection : Nature Communications : Nature Publishing Group | plant pathogen interactions | Scoop.it

To cause plant disease, pathogenic fungi can secrete effector proteins into plant cells to suppress plant immunity and facilitate fungal infection. Most fungal pathogens infect plants using very long strand-like cells, called hyphae, that secrete effectors from their tips into host tissue. How fungi undergo long-distance cell signalling to regulate effector production during infection is not known. Here we show that long-distance retrograde motility of early endosomes (EEs) is necessary to trigger transcription of effector-encoding genes during plant infection by the pathogenic fungusUstilago maydis. We demonstrate that motor-dependent retrograde EE motility is necessary for regulation of effector production and secretion during host cell invasion. We further show that retrograde signalling involves the mitogen-activated kinase Crk1 that travels on EEs and participates in control of effector production. Fungal pathogens therefore undergo long-range signalling to orchestrate host invasion.

James Hane's insight:

good candidates for novel fungicide targets

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Silencing the mob: disrupting quorum sensing as a means to fight plant disease -

Silencing the mob: disrupting quorum sensing as a means to fight plant disease - | plant pathogen interactions | Scoop.it

Bacteria are able to sense their population's density through a cell–cell communication system, termed ‘quorum sensing’ (QS). This system regulates gene expression in response to cell density through the constant production and detection of signalling molecules. These molecules commonly act as auto-inducers through the up-regulation of their own synthesis. Many pathogenic bacteria, including those of plants, rely on this communication system for infection of their hosts. The finding that the countering of QS-disrupting mechanisms exists in many prokaryotic and eukaryotic organisms offers a promising novel method to fight disease. During the last decade, several approaches have been proposed to disrupt QS pathways of phytopathogens, and hence to reduce their virulence. Such studies have had varied success in vivo, but most lend promising support to the idea that QS manipulation could be a potentially effective method to reduce bacterial-mediated plant disease. This review discusses the various QS-disrupting mechanisms found in both bacteria and plants, as well as the different approaches applied artificially to interfere with QS pathways and thus protect plant health.


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The Vip1 Inositol Polyphosphate Kinase Family Regulates Polarized Growth and Modulates the Microtubule Cytoskeleton in Fungi

The Vip1 Inositol Polyphosphate Kinase Family Regulates Polarized Growth and Modulates the Microtubule Cytoskeleton in Fungi | plant pathogen interactions | Scoop.it

Microtubules (MTs) are pivotal for numerous eukaryotic processes ranging from cellular morphogenesis, chromosome segregation to intracellular transport. Execution of these tasks requires intricate regulation of MT dynamics. Here, we identify a new regulator of the Schizosaccharomyces pombe MT cytoskeleton: Asp1, a member of the highly conserved Vip1 inositol polyphosphate kinase family. Inositol pyrophosphates generated by Asp1 modulate MT dynamic parameters independent of the central +TIP EB1 and in a dose-dependent and cellular-context-dependent manner. Importantly, our analysis of the in vitro kinase activities of various S. pombe Asp1 variants demonstrated that the C-terminal phosphatase-like domain of the dual domain Vip1 protein negatively affects the inositol pyrophosphate output of the N-terminal kinase domain. These data suggest that the former domain has phosphatase activity. Remarkably, Vip1 regulation of the MT cytoskeleton is a conserved feature, as Vip1-like proteins of the filamentous ascomycete Aspergillus nidulans and the distantly related pathogenic basidiomycete Ustilago maydis also affect the MT cytoskeleton in these organisms. Consistent with the role of interphase MTs in growth zone selection/maintenance, all 3 fungal systems show aspects of aberrant cell morphogenesis. Thus, for the first time we have identified a conserved biological process for inositol pyrophosphates.

Author Summary

Fungi are an extremely successful and diverse group of organisms ranging from the small single-celled yeasts to the indefinitely growing filamentous fungi. Polarized growth, where growth is restricted to defined regions, leads to the specific cell shape of yeast cells, as well as the very long hyphae of filamentous fungi. Fungal polar growth is controlled by an internal regulatory circuit of which the microtubule cytoskeleton comprises the transport road for numerous cargos needed for polarized growth. However, the microtubule cytoskeleton is not static, but a dynamic structure, which is modulated by microtubule-associated proteins and the interaction with other cellular structures. Our present analysis has identified a new regulator of the microtubule cytoskeleton in the fission yeast S. pombe: a member of the highly conserved Vip1 inositol polyphosphate kinase family. Vip1 proteins have a dual domain structure consisting of an N-terminal kinase domain which synthesizes inositol pyrophosphates and a C-terminal domain, which we show to negatively regulate the kinase output. Our results suggest that modulation of microtubule dynamics is correlated to Vip1 kinase activity. Importantly, polarized growth and microtubule dynamics were also modulated by Vip1 family members in A. nidulans and U. maydis thus uncovering a conserved biological role for inositol pyrophosphates.


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MPMI: Mycosphaerella graminicola LysM effector-mediated stealth pathogenesis subverts recognition through both CERK1 and CEBiP homologues in wheat (2013)

MPMI: Mycosphaerella graminicola LysM effector-mediated stealth pathogenesis subverts recognition through both CERK1 and CEBiP homologues in wheat (2013) | plant pathogen interactions | Scoop.it

Fungal cell wall chitin is a well-recognized pathogen-associated molecular pattern. Recognition of chitin in plants by pattern recognition receptors activates pathogen triggered immunity (PTI). In Arabidopsis this process is mediated by a plasma membrane receptor kinase CERK1, whereas in rice a receptor-like protein CEBiP in addition to CERK1 is required. Secreted chitin-binding lysin motif (LysM) containing fungal effector proteins such as Ecp6 from the biotrophic fungusCladosporium fulvum have been reported to interfere with PTI. Here we identified wheat homologues of CERK1 and CEBiP and investigated their role in the interaction with the non-biotrophic pathogen of wheatMycosphaerella graminicola (synonym Zymoseptoria tritici). We show that silencing of either CERK1 or CEBiP in wheat using Barley stripe mosaic virus-mediated Virus-induced gene silencing (BSMV-VIGS) is sufficient in allowing leaf colonization by the normally nonpathogenic M. graminicola Mg3LysM (homologue of Ecp6) deletion mutant, while theMg1LysM deletion mutant was fully pathogenic toward both silenced and wild type wheat leaves. These data indicate that Mg3LysM is important for fungal evasion of PTI in wheat leaf tissue and that both CERK1 and CEBiP are required for activation of chitin-induced defenses, a feature conserved between rice and wheat, and also perhaps in other cereal species.


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Stephen Bolus's curator insight, February 10, 1:52 AM

I want to do VIGS on wheat!

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SearchSmallRNA: a graphical interface tool for the assemblage of viral genomes using small RNA libraries data - Virology Journal

SearchSmallRNA: a graphical interface tool for the assemblage of viral genomes using small RNA libraries data - Virology Journal | plant pathogen interactions | Scoop.it
Next-generation parallel sequencing (NGS) allows the identification of viral pathogens by sequencing the small RNAs of infected hosts. Thus, viral genomes may be assembled from host immune response products without prior virus enrichment, amplification or purification. However, mapping of the vast information obtained presents a bioinformatics challenge.

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Nature Biotechnology: Wheat rescued from fungal disease (2014)

Nature Biotechnology: Wheat rescued from fungal disease (2014) | plant pathogen interactions | Scoop.it

Knockout of all six alleles of a gene in the large wheat genome confers resistance to powdery mildew --- Genetic engineering to improve crops is entering a new era as conventional transgenesis technology, which involves random insertion of genes into the genome, is superseded by newer approaches that enable precise genetic alterations. A particular technological challenge in carrying out targeted genome modification in crops is that many plant genomes are polyploid, including such important species as wheat, potato and canola1. In this issue, Wang et al.2 report engineering of the hexaploid wheat genome using sequence-specific nucleases (SSNs)—the first demonstration in a polyploid crop of SSN-mediated genetic alterations that are stably transmitted to the next generation. By knocking out all six alleles encoding the MILDEW-RESISTANCE LOCUS (MLO) protein, the authors generated a mutant line that shows strong resistance to powdery mildew, a devastating fungal disease. This is a remarkable feat, given the ploidy and enormous size (17.1 Gb) of the wheat genome, and showcases the power of SSNs for engineering complex plant genomes and for creating crops with valuable traits.


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Ten Simple Rules for Better Figures

Ten Simple Rules for Better Figures | plant pathogen interactions | Scoop.it

"Scientific visualization is classically defined as the process of graphically displaying scientific data. However, this process is far from direct or automatic. There are so many different ways to represent the same data: scatter plots, linear plots, bar plots, and pie charts, to name just a few. Furthermore, the same data, using the same type of plot, may be perceived very differently depending on who is looking at the figure. A more accurate definition for scientific visualization would be a graphical interface between people and data. In this short article, we do not pretend to explain everything about this interface; rather, see [1], [2] for introductory work. Instead we aim to provide a basic set of rules to improve figure design and to explain some of the common pitfalls."


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New Phytologist: TAL effectors – pathogen strategies and plant resistance engineering (2014)

New Phytologist: TAL effectors – pathogen strategies and plant resistance engineering (2014) | plant pathogen interactions | Scoop.it

Transcription activator-like effectors (TALEs) from plant pathogenic Xanthomonas spp. and the related RipTALs from Ralstonia solanacearum are DNA-binding proteins with a modular DNA-binding domain. This domain is both predictable and programmable, which simplifies elucidation of TALE function in planta and facilitates generation of DNA-binding modules with desired specificity for biotechnological approaches. Recently identified TALE host target genes that either promote or stop bacterial disease provide new insights into how expression of TALE genes affects the plant–pathogen interaction. Since its elucidation the TALE code has been continuously refined and now provides a mature tool that, in combination with transcriptome profiling, allows rapid isolation of novel TALE target genes. The TALE code is also the basis for synthetic promoter-traps that mediate recognition of TALE or RipTAL proteins in engineered plants. In this review, we will summarize recent findings in plant-focused TALE research. In addition, we will provide an outline of the newly established gene isolation approach for TALE or RipTAL host target genes with an emphasis on potential pitfalls.


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PLOS Biology: Transient Hypermutagenesis Accelerates the Evolution of Legume Endosymbionts following Horizontal Gene Transfer (2014)

PLOS Biology: Transient Hypermutagenesis Accelerates the Evolution of Legume Endosymbionts following Horizontal Gene Transfer (2014) | plant pathogen interactions | Scoop.it

Horizontal gene transfer (HGT) is an important mode of adaptation and diversification of prokaryotes and eukaryotes and a major event underlying the emergence of bacterial pathogens and mutualists. Yet it remains unclear how complex phenotypic traits such as the ability to fix nitrogen with legumes have successfully spread over large phylogenetic distances. Here we show, using experimental evolution coupled with whole genome sequencing, that co-transfer of imuABC error-prone DNA polymerase genes with key symbiotic genes accelerates the evolution of a soil bacterium into a legume symbiont. Following introduction of the symbiotic plasmid of Cupriavidus taiwanensis, the Mimosasymbiont, into pathogenic Ralstonia solanacearum we challenged transconjugants to become Mimosa symbionts through serial plant-bacteria co-cultures. We demonstrate that a mutagenesis imuABC cassette encoded on the C. taiwanensis symbiotic plasmid triggered a transient hypermutability stage in R. solanacearum transconjugants that occurred before the cells entered the plant. The generated burst in genetic diversity accelerated symbiotic adaptation of the recipient genome under plant selection pressure, presumably by improving the exploration of the fitness landscape. Finally, we show that plasmid imuABC cassettes are over-represented in rhizobial lineages harboring symbiotic plasmids. Our findings shed light on a mechanism that may have facilitated the dissemination of symbiotic competency among α- and β-proteobacteria in natura and provide evidence for the positive role of environment-induced mutagenesis in the acquisition of a complex lifestyle trait. We speculate that co-transfer of complex phenotypic traits with mutagenesis determinants might frequently enhance the ecological success of HGT.

 

See also Symbiosis Plasmids Bring Their Own Mutagen to the Wedding Party http://dx.plos.org/10.1371/journal.pbio.1001943


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Markov Chains

A visual explanation by Victor Powell/w text by Lewis Lehe


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ABC News: Canola virus wipes out crops in South Australia (2014)

ABC News: Canola virus wipes out crops in South Australia (2014) | plant pathogen interactions | Scoop.it

Scientists say an outbreak of beet western yellows virus is one of the worst cases ever seen in Australia.

 

Early estimates suggest up to 10,000 hectares of canola have been affected, in South Australia's lower north, mid north and lower mallee regions. The virus is transported by green peach aphids, which have thrived in the state's recent warm and humid weather. Ag consultant Mick Faulkner says agronomists felt like they'd been "blind-sided" after not being able to work out what had been affecting crops. "It took everyone a fair bit of time to realise that we weren't killing the aphids," Mr Faulkner said. "Green paddocks are now brown. "Those that have been affected, I have grave fears that they won't yield anything at all."

 

Virus halted for now - The South Australian Research and Development Institute (SARDI) says it's now testing samples to confirm how the virus is spreading and where else it might turn up. Pulse pathologist Jenny Davidson says with cooler weather, the virus-transmitting aphids aren't moving and at the moment the best thing growers can do is "nothing", "We expect that the spread of this virus would've stopped for now, so there's no point people going out and spraying aphids now," she says. "It's also important growers ascertain it actually is the virus causing problems in their canola crops, there may be other things going on as well. "The potential risk is what these aphids will do in spring time. "We're not sure whether or not pulse crops are at risk but we'll have that information back well and truly before the spring time flights." Ms Davidson says the virus isn't uncommon, but what is unusual is the extent of damage and infection being seen. She says it's taken everyone by surprise. "I've never seen this level of damage from any virus in crops," Ms Davidson says. "It's the magnitude of what we're dealing with that is totally un-expected."


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Nature Biotechnology: Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew (2014)

Nature Biotechnology: Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew (2014) | plant pathogen interactions | Scoop.it

Sequence-specific nucleases have been applied toengineer targeted modifications in polyploid genomes, but simultaneous modification of multiple homoeoalleles has not been reported. Here we use transcription activator–like effector nuclease (TALEN) and clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 technologies in hexaploid bread wheat to introduce targeted mutations in the three homoeoalleles that encode MILDEW- RESISTANCE LOCUS (MLO) proteins. Genetic redundancy has prevented evaluation of whether mutation of all three MLO alleles in bread wheat might confer resistance to powdery mildew, a trait not found in natural populations. We show that TALEN-induced mutation of all three TaMLO homoeologs in the same plant confers heritable broad-spectrum resistanceto powdery mildew. We further use CRISPR-Cas9 technologyto generate transgenic wheat plants that carry mutations inthe TaMLO-A1 allele. We also demonstrate the feasibility of engineering targeted DNA insertion in bread wheat through nonhomologous end joining of the double-strand breaks caused by TALENs. Our findings provide a methodological framework to improve polyploid crops.

 


Via dromius, Kamoun Lab @ TSL
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Fesquet didier's curator insight, July 22, 5:22 AM

this open the way for developping non toxic wheat species...good for celiac people...maybe one day...hopes for a slice of pizza :-)

 

Mary Williams's curator insight, July 31, 6:33 AM

I'm trying to catch up with what I missed while traveling. I think this is one of the more exciting papers that came out in the past few weeks, and I'm a bit surprised that it didn't get more press coverage.