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Emerging Research in Plant Cell Biology
A science editor's take on what's new and interesting in the plant kingdom.
Curated by Jennifer Mach
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Arabidopsis uses two gluconeogenic gateways for organic acids to fuel seedling establishment

Arabidopsis uses two gluconeogenic gateways for organic acids to fuel seedling establishment | Emerging Research in Plant Cell Biology | Scoop.it

Gluconeogenesis is a fundamental metabolic process that allows organisms to make sugars from non-carbohydrate stores such as lipids and protein. In eukaryotes only one gluconeogenic route has been described from organic acid intermediates and this relies on the enzyme phosphoenolpyruvate carboxykinase (PCK). Here we show that two routes exist in Arabidopsis, and that the second uses pyruvate, orthophosphate dikinase (PPDK). Gluconeogenesis is critical to fuel the transition from seed to seedling. Arabidopsis pck1 and ppdk mutants are compromised in seed-storage reserve mobilization and seedling establishment. Radiolabelling studies show that PCK predominantly allows sugars to be made from dicarboxylic acids, which are products of lipid breakdown. However, PPDK also allows sugars to be made from pyruvate, which is a major product of protein breakdown. We propose that both routes have been evolutionarily conserved in plants because, while PCK expends less energy, PPDK is twice as efficient at recovering carbon from pyruvate.

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Flowering time and seed dormancy control use external coincidence to generate life history strategy

Flowering time and seed dormancy control use external coincidence to generate life history strategy | Emerging Research in Plant Cell Biology | Scoop.it

Climate change is accelerating plant developmental transitions coordinated with the seasons in temperate environments. To understand the importance of these timing advances for a stable life history strategy, we constructed a full life cycle model of Arabidopsis thaliana. Modelling and field data reveal that a cryptic function of flowering time control is to limit seed set of winter annuals to an ambient temperature window which coincides with a temperature-sensitive switch in seed dormancy state. This coincidence is predicted to be conserved independent of climate at the expense of flowering date, suggesting that temperature control of flowering time has evolved to constrain seed set environment and therefore frequency of dormant and non-dormant seed states. We show that late flowering can disrupt this bet-hedging germination strategy. Our analysis shows that life history modelling can reveal hidden fitness constraints and identify non-obvious selection pressures as emergent features.

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The future of starch bioengineering: GM microorganisms or GM plants?

Plant starches regularly require extensive modification to permit subsequent applications. Such processing is usually done by the use of chemical and/or physical treatments. The use of recombinant enzymes produced by large-scale fermentation of GM microorganisms is increasingly used in starch processing and modification, sometimes as an alternative to chemical or physical treatments.

 

However, as a means to impart the modifications as early as possible in the starch production chain, similar recombinant enzymes may also be expressed in planta in the developing starch storage organ such as in roots, tubers and cereal grains to provide a GM crop as an alternative to the use of enzymes from GM microorganisms... In planta starch bioengineering is generally challenged by yield penalties and inefficient production of the desired product. However in some situations, GM crops for starch bioengineering without deleterious effects have been achieved...

 

We have compared the use of starch modifying enzymes produced by GM microrganisms with the expression of these enzymes directly in crops. In summary we find that in planta starch bioengineering by expression of starch modifying enzymes directly in crop storage organs faces a number of challenges that need to be addressed further. In particular, starch bioengineering may sometimes be associated with significant yield loss...

 

Only a few studies have been carried through to agronomic field trials. The physiological conditions in amyloplasts of crop starch organs may not be optimal for starch modifying enzymes of non-plant origin, and in several studies only very small amounts of the desired product is formed. However, the method looks promising for situations where the transgenic enzymes remain inactive during crop development, so that the above mentioned deleterious effects are avoided.

 

For example crops expressing thermophilic hydrolytic enzymes, which are activated by heat, have been shown to reduce production costs and energy and water usage of grain processing. Other methods of “post-harvest” activation of transgenic enzymes in crops could be explored. In other situations there may not be a biotechnological alternative to transgenic enzyme expression directly in developing crop organs. For example starch kinases have been used to increase starch phosphate content in cereal grains and in potatoes, whereas there are currently no reports that a similar modification can be made during post-harvest starch processing... 

 

http://journal.frontiersin.org/article/10.3389/fpls.2015.00247/abstract

 


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Chromosome Replacement and Deletion Lead to Clonal Polymorphism of Berry Color in Grapevine

Chromosome Replacement and Deletion Lead to Clonal Polymorphism of Berry Color in Grapevine | Emerging Research in Plant Cell Biology | Scoop.it
Author Summary Pinot is one of the most ancient grapevine varieties made up of a large panel of clones, most of them used to produce very different wines with specific oenological characteristics in different vineyards around the world. This great diversity of clones, which is due to spontaneous somatic mutations that have occurred over time, makes Pinot a fascinating subject of study. It is the reason why we have undertaken a study focused on the color locus to identify the mutations responsible for color variation in a large panel of Pinot gris and Pinot blanc clones. The results we obtained shed light on large-scale molecular events that account for the loss of anthocyanin biosynthesis, such as chromosome replacement and deletion. These mutations first multiplied and, depending on the cell layer in which they occurred, lead to chimeras. Occasionally, cell layer rearrangements homogenize the whole plant. Clonal polymorphism of grapevine varieties results from a succession of such molecular and cellular mechanisms that are the driving forces behind the genetic drift of clones and the evolution of the grapevine genome.
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The Extent and Consequences of P-Hacking in Science

The Extent and Consequences of P-Hacking in Science | Emerging Research in Plant Cell Biology | Scoop.it
Publication bias resulting from so-called "p-hacking" is pervasive throughout the life sciences; however, its effects on general conclusions made from the literature appear to be weak.
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Endogenous Arabidopsis messenger RNAs transported to distant tissues

Endogenous Arabidopsis messenger RNAs transported to distant tissues | Emerging Research in Plant Cell Biology | Scoop.it

The concept that proteins and small RNAs can move to and function in distant body parts is well established. However, non-cell-autonomy of small RNA molecules raises the question: To what extent are protein-coding messenger RNAs (mRNAs) exchanged between tissues in plants? Here we report the comprehensive identification of 2,006 genes producing mobile RNAs in Arabidopsis thaliana. The analysis of variant ecotype transcripts that were present in heterografted plants allowed the identification of mRNAs moving between various organs under normal or nutrient-limiting conditions. Most of these mobile transcripts seem to follow the phloem-dependent allocation pathway transporting sugars from photosynthetic tissues to roots via the vasculature. Notably, a high number of transcripts also move in the opposite, root-to-shoot direction and are transported to specific tissues including flowers. Proteomic data on grafted plants indicate the presence of proteins from mobile RNAs, allowing the possibility that they may be translated at their destination site. The mobility of a high number of mRNAs suggests that a postulated tissue-specific gene expression profile might not be predictive for the actual plant body part in which a transcript exerts its function

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Guojian HU's curator insight, March 26, 4:31 AM

attractive!

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Phosphorus limitation, soil-borne pathogens and the coexistence of plant species in hyperdiverse forests and shrublands-- Tansley review.

Phosphorus limitation, soil-borne pathogens and the coexistence of plant species in hyperdiverse forests and shrublands-- Tansley review. | Emerging Research in Plant Cell Biology | Scoop.it

Hyperdiverse forests occur in the lowland tropics, whereas the most species-rich shrublands are found in regions such as south-western Australia (kwongan) and South Africa (fynbos). Despite large differences, these ecosystems share an important characteristic: their soils are strongly weathered and phosphorus (P) is a key growth-limiting nutrient. Soil-borne pathogens are increasingly being recognized as drivers of plant diversity in lowland tropical rainforests, but have received little attention in species-rich shrublands. We suggest a trade-off in which the species most proficient at acquiring P have ephemeral roots that are particularly susceptible to soil-borne pathogens. This could equalize out the differences in competitive ability among co-occurring species in these ecosystems, thus contributing to coexistence. Moreover, effective protection against soil-borne pathogens by ectomycorrhizal (ECM) fungi might explain the occurrence of monodominant stands of ECM trees and shrubs amongst otherwise species-rich communities. We identify gaps in our knowledge which need to be filled in order to evaluate a possible link between P limitation, fine root traits, soil-borne pathogens and local plant species diversity. Such a link may help to explain how numerous plant species can coexist in hyperdiverse rainforests and shrublands, and, conversely, how monodominant stands can develop in these ecosystems.

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Redefining fine roots improves understanding of below-ground contributions to terrestrial biosphere processes

Redefining fine roots improves understanding of below-ground contributions to terrestrial biosphere processes | Emerging Research in Plant Cell Biology | Scoop.it
Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain because of the challenges of consistently measuring and interpreting fine-root systems. Traditionally, fine roots have been defined as all roots ≤ 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. Here, we demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are either separated into individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine-root pool. Using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally – a c. 30% reduction from previous estimates assuming a single fine-root pool. Future work developing tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi into fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand below-ground processes in the terrestrial biosphere.

Via Christophe Jacquet
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Importance of tyrosine phosphorylation in receptor kinase complexes

Importance of tyrosine phosphorylation in receptor kinase complexes | Emerging Research in Plant Cell Biology | Scoop.it
Tyrosine phosphorylation is an important post-translational modification that is known to regulate receptor kinase (RK)-mediated signaling in animals. Plant RKs are annotated as serine/threonine kinases, but recent work has revealed that tyrosine phosphorylation is also crucial for the activation of RK-mediated signaling in plants. These initial observations have paved the way for subsequent detailed studies on the mechanism of activation of plant RKs and the biological relevance of tyrosine phosphorylation for plant growth and immunity. In this Opinion article we review recent reports on the contribution of RK tyrosine phosphorylation in plant growth and immunity; we propose that tyrosine phosphorylation plays a major regulatory role in the initiation and transduction of RK-mediated signaling in plants.

Via Jean-Michel Ané
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Punctual Transcriptional Regulation by the Rice Circadian Clock under Fluctuating Field Conditions (Plant Cell)

Punctual Transcriptional Regulation by the Rice Circadian Clock under Fluctuating Field Conditions (Plant Cell) | Emerging Research in Plant Cell Biology | Scoop.it

Using hundreds of samples of field-grown rice (Oryza sativa) leaves, we developed a statistical model for the expression of circadian clock-related genes integrating diurnally entrained circadian clock with phase setting by light, both responses to light and temperature gated by the circadian clock. We show that expression of individual genes was strongly affected by temperature. However, internal time estimated from expression of multiple genes, which may reflect transcriptional regulation of downstream genes, is punctual to 22 min and not affected by weather, daylength, or plant developmental age in the field. Thus, we demonstrated that the circadian clock is a regulatory network of multiple genes that retains accurate physical time of day by integrating the perturbations on individual genes under fluctuating environments in the field.


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Nat. Commun.: Bacterial killing via a type IV secretion system (2015)

Nat. Commun.: Bacterial killing via a type IV secretion system (2015) | Emerging Research in Plant Cell Biology | Scoop.it

http://www.nature.com/ncomms/2015/150306/ncomms7453/full/ncomms7453.html?WT.ec_id=NCOMMS-20150311

 

Type IV secretion systems (T4SSs) are multiprotein complexes that transport effector proteins and protein–DNA complexes through bacterial membranes to the extracellular milieu or directly into the cytoplasm of other cells. Many bacteria of the family Xanthomonadaceae, which occupy diverse environmental niches, carry a T4SS with unknown function but with several characteristics that distinguishes it from other T4SSs. Here we show that the Xanthomonas citri T4SS provides these cells the capacity to kill other Gram-negative bacterial species in a contact-dependent manner. The secretion of one type IV bacterial effector protein is shown to require a conserved C-terminal domain and its bacteriolytic activity is neutralized by a cognate immunity protein whose 3D structure is similar to peptidoglycan hydrolase inhibitors. This is the first demonstration of the involvement of a T4SS in bacterial killing and points to this special class of T4SS as a mediator of both antagonistic and cooperative interbacterial interactions.

 

Diorge P. Souza, Gabriel U. Oka, Cristina E. Alvarez-Martinez, Alexandre W. Bisson-Filho, German Dunger, Lise Hobeika, Nayara S. Cavalcante, Marcos C. Alegria, Leandro R.S. Barbosa, Roberto K. Salinas, Cristiane R. Guzzo & Chuck S. Farah


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Nature Biotechnology: Engineering insect-free cereals (2015)

Nature Biotechnology: Engineering insect-free cereals (2015) | Emerging Research in Plant Cell Biology | Scoop.it

A cluster of three rice lectin receptor kinases confers resistance to planthopper insects.

 

Insect pests reduce yields of crops worldwide through direct damage and because they spread devastating viral diseases. In Asia, the brown planthopper (BPH) decimates rice (Oryza sativa) crops, causing the loss of billions of dollars annually1. In this issue, Liu et al.2 report the cloning of a rice genetic locus that confers broad-spectrum resistance to BPH and at least one other planthopper species (white back planthopper). Introducing this locus into plant genomes is likely to provide an effective means of combating insect pests of rice and of other cereals such as maize.

 

In modern rice agriculture, BPH damage is controlled through breeding and the application of vast amounts of chemical pesticides1. Pesticides are not a sustainable approach, however, owing to high costs, harmful environmental effects and rapid development of resistant insects. Breeding programs have identified more than 20 genetic loci in cultivated or wild rice species that confer BPH resistance1. However, these Bph loci are usually only effective against specific BPH biotypes, and newly evolved BPH populations have rapidly overcome several Bph resistance loci deployed in the field..

 

Of the >20 identified Bph loci, only Bph14 and Bph26 have been cloned. Both of these loci encode coiled-coil, nucleotide-binding and leucine-rich repeat proteins3, 4, the main class of plant intracellular immune receptors5. Bph3 is a resistance locus that was first pinpointed genetically in the Sri Lankan rice indica cultivar Rathu Heenati. Notably, unlike most other Bph loci, including Bph14 and Bph26, Bph3 confers broad-spectrum resistance to many BPH biotypes as well as to the white back planthopper1, 2. The success of Bph3 as a resistance locus might be linked to the fact that it acts against BPH at an early stage of the feeding cycle, before the insect can deploy its arsenal of virulence proteins that circumvent plant defenses.

 

Despite the huge potential of Bph3 for rice agriculture, its molecular identity has been unknown. Liu et al.2 now identify Bph3 through map-based cloning in a cross between the resistant indica cultivar Rathu Heenati and the susceptible japonica cultivar 02428. Bph3 maps to a 79-kb genomic region that contains a cluster of three lectin receptor kinases, OsLecRK1–3 (ref. 2) (Fig. 1). The authors find that single-nucleotide polymorphisms in these genes are associated with BPH resistance in different cultivated rice accessions. They also show that ectopic expression of the OsLecRK1–3 gene cluster in the susceptible japonica Kitaake cultivar confers BPH resistance.

 

See Liu et al. Nature Biotechnology http://www.nature.com/nbt/journal/v33/n3/full/nbt.3069.html


Via Kamoun Lab @ TSL, Francis Martin, Christophe Jacquet, Mary Williams
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A gene cluster encoding lectin receptor kinases confers broad-spectrum and durable insect resistance in rice

A gene cluster encoding lectin receptor kinases confers broad-spectrum and durable insect resistance in rice | Emerging Research in Plant Cell Biology | Scoop.it

The brown planthopper (BPH) is the most destructive pest of rice (Oryza sativa) and a substantial threat to rice production, causing losses of billions of dollars annually1, 2. Breeding of resistant cultivars is currently hampered by the rapid breakdown of BPH resistance2. Thus, there is an urgent need to identify…

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So not open-access that Nature Biotech doesn't even give you the full abstract.

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Beyond the thale: comparative genomics and genetics of Arabidopsis relatives

Beyond the thale: comparative genomics and genetics of Arabidopsis relatives | Emerging Research in Plant Cell Biology | Scoop.it

For decades a small number of model species have rightly occupied a privileged position in laboratory experiments, but it is becoming increasingly clear that our knowledge of biology is greatly improved when informed by a broader diversity of species and evolutionary context.Arabidopsis thaliana has been the primary model organism for plants, benefiting from a high-quality reference genome sequence and resources for reverse genetics. However, recent studies have made a group of species also in the Brassicaceae family and closely related to A. thaliana a focal point for comparative molecular, genomic, phenotypic and evolutionary studies. In this Review, we emphasize how such studies complement continued study of the model plant itself, provide an evolutionary perspective and summarize our current understanding of genetic and phenotypic diversity in plants.

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Best #title ever.

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A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress

A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress | Emerging Research in Plant Cell Biology | Scoop.it
The plasticity of root architecture is crucial for plants to acclimate to unfavourable environments including low nitrogen (LN) stress. How maize roots coordinate the growth of axile roots and lateral roots (LRs), as well as longitudinal and radial cell behaviours in response to LN stress, remains unclear. Maize plants were cultivated hydroponically under control (4 mm nitrate) and LN (40 μm) conditions. Temporal and spatial samples were taken to analyse changes in the morphology, anatomical structure and carbon/nitrogen (C/N) ratio in the axile root and LRs. LN stress increased axile root elongation, reduced the number of crown roots and decreased LR density and length. LN stress extended cell elongation zones and increased the mature cell length in the roots. LN stress reduced the cell diameter and total area of vessels and increased the amount of aerenchyma, but the number of cell layers in the crown root cortex was unchanged. The C/N ratio was higher in the axile roots than in the LRs. Maize roots acclimate to LN stress by optimizing the anatomical structure and N allocation. As a result, axile root elongation is favoured to efficiently find available N in the soil.

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Arabidopsis BREVIPEDICELLUS Interacts with the SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA to Regulate KNAT2 and KNAT6 Expression in Control of Inflorescence Architecture

Arabidopsis  BREVIPEDICELLUS Interacts with the SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA to Regulate  KNAT2  and  KNAT6  Expression in Control of Inflorescence Architecture | Emerging Research in Plant Cell Biology | Scoop.it
Author Summary BP is a class-I KNOX transcription factor that controls normal inflorescence architecture development by repressing the expression of two KNOX genes, KNAT2 and KNAT6 . In this study, we showed that Arabidopsis BP directly interacts with the SWI2/SNF2 chromatin remodeling ATPase BRM. brm and bp mutants displayed similar inflorescence architecture defects, with clustered inflorescences, horizontally orientated pedicels, and short pedicels and internodes. Furthermore, BP and BRM co-target to KNAT2 and KNAT6 genes and repress their expression. This work reveals a new regulatory mechanism that BP associates with BRM in control of inflorescence architecture development.
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Stomatal Guard Cells Co-opted an Ancient ABA-Dependent Desiccation Survival System to Regulate Stomatal Closure

During the transition from water to land, plants had to cope with the loss of water through transpiration, the inevitable result of photosynthetic CO2 fixation on land [ 1, 2 ]. Control of transpiration became possible through the development of a new cell type: guard cells, which form stomata. In vascular plants, stomatal regulation is mediated by the stress hormone ABA, which triggers the opening of the SnR kinase OST1-activated anion channel SLAC1 [ 3, 4 ]. To understand the evolution of this regulatory circuit, we cloned both ABA-signaling elements, SLAC1 and OST1, from a charophyte alga, a liverwort, and a moss, and functionally analyzed the channel-kinase interactions. We were able to show that the emergence of stomata in the last common ancestor of mosses and vascular plants coincided with the origin of SLAC1-type channels capable of using the ancient ABA drought signaling kinase OST1 for regulation of stomatal closure.


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Plants regenerated from tissue culture contain stable epigenome changes in rice

Plants regenerated from tissue culture contain stable epigenome changes in rice | Emerging Research in Plant Cell Biology | Scoop.it

Most transgenic crops are produced through tissue culture. The impact of utilizing such methods on the plant epigenome is poorly understood. Here we generated whole-genome, single-nucleotide resolution maps of DNA methylation in several regenerated rice lines. We found that all tested regenerated plants had significant losses of methylation compared to non-regenerated plants. Loss of methylation was largely stable across generations, and certain sites in the genome were particularly susceptible to loss of methylation. Loss of methylation at promoters was associated with deregulated expression of protein-coding genes. Analyses of callus and untransformed plants regenerated from callus indicated that loss of methylation is stochastically induced at the tissue culture step. These changes in methylation may explain a component of somaclonal variation, a phenomenon in which plants derived from tissue culture manifest phenotypic variability.

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Okay, "Plants.... in rice"? #titletrouble

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Primary transcripts of microRNAs encode regulatory peptides

Primary transcripts of microRNAs encode regulatory peptides | Emerging Research in Plant Cell Biology | Scoop.it

MicroRNAs (miRNAs) are small regulatory RNA molecules that inhibit the expression of specific target genes by binding to and cleaving their messenger RNAs or otherwise inhibiting their translation into proteins1. miRNAs are transcribed as much larger primary transcripts (pri-miRNAs), the function of which is not fully understood. Here we show that plant pri-miRNAs contain short open reading frame sequences that encode regulatory peptides. The pri-miR171b ofMedicago truncatula and the pri-miR165a of Arabidopsis thaliana produce peptides, which we term miPEP171b and miPEP165a, respectively, that enhance the accumulation of their corresponding mature miRNAs, resulting in downregulation of target genes involved in root development. The mechanism of miRNA-encoded peptide (miPEP) action involves increasing transcription of the pri-miRNA. Five other pri-miRNAs of A. thaliana and M. truncatula encode active miPEPs, suggesting that miPEPs are widespread throughout the plant kingdom. Synthetic miPEP171b and miPEP165a peptides applied to plants specifically trigger the accumulation of miR171b and miR165a, leading to reduction of lateral root development and stimulation of main root growth, respectively, suggesting that miPEPs might have agronomical applications.

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Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat

Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat | Emerging Research in Plant Cell Biology | Scoop.it
Perception of pathogen (or microbe)-associated molecular patterns (PAMPs/MAMPs) by pattern recognition receptors (PRRs) is a key component of plant innate immunity. The Arabidopsis PRR EF-Tu receptor (EFR) recognizes the bacterial PAMP elongation factor Tu (EF-Tu) and its derived peptide elf18. Previous work revealed that transgenic expression of AtEFR in Solanaceae confers elf18 responsiveness and broad-spectrum bacterial disease resistance.
In this study, we developed a set of bioassays to study the activation of PAMP-triggered immunity (PTI) in wheat. We generated transgenic wheat (Triticum aestivum) plants expressing AtEFR driven by the constitutive rice actin promoter and tested their response to elf18.
We show that transgenic expression of AtEFR in wheat confers recognition of elf18, as measured by the induction of immune marker genes and callose deposition. When challenged with the cereal bacterial pathogen Pseudomonas syringae pv. oryzae, transgenic EFR wheat lines had reduced lesion size and bacterial multiplication.
These results demonstrate that AtEFR can be transferred successfully from dicot to monocot species, further revealing that immune signalling pathways are conserved across these distant phyla. As novel PRRs are identified, their transfer between plant families represents a useful strategy for enhancing resistance to pathogens in crops.

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Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2 : Scientific Reports : Nature Publishing Group

Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2 : Scientific Reports : Nature Publishing Group | Emerging Research in Plant Cell Biology | Scoop.it

Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO2, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO2 (eCO2) through optimizing functioning of the root-soil interface. By using a labeling technique with 13C and 15N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO2. These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO2 effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO2. The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.


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Stomatal Guard Cells Co-opted an Ancient ABA-Dependent Desiccation Survival System to Regulate Stomatal Closure

During the transition from water to land, plants had to cope with the loss of water through transpiration, the inevitable result of photosynthetic CO2 fixation on land [ 1, 2 ]. Control of transpiration became possible through the development of a new cell type: guard cells, which form stomata. In vascular plants, stomatal regulation is mediated by the stress hormone ABA, which triggers the opening of the SnR kinase OST1-activated anion channel SLAC1 [ 3, 4 ]. To understand the evolution of this regulatory circuit, we cloned both ABA-signaling elements, SLAC1 and OST1, from a charophyte alga, a liverwort, and a moss, and functionally analyzed the channel-kinase interactions. We were able to show that the emergence of stomata in the last common ancestor of mosses and vascular plants coincided with the origin of SLAC1-type channels capable of using the ancient ABA drought signaling kinase OST1 for regulation of stomatal closure.


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MPMI: Focus on The Good, the Bad and the Unknown: Genomics-Enabled Discovery of Plant-Associated Microbial Processes and Diversity (2015)

MPMI: Focus on The Good, the Bad and the Unknown: Genomics-Enabled Discovery of Plant-Associated Microbial Processes and Diversity (2015) | Emerging Research in Plant Cell Biology | Scoop.it

MPMI has played a leading role in disseminating new insights into plant-microbe interactions and promoting new approaches. Articles in this Focus Issue highlight the power of genomic studies in uncovering novel determinants of plant interactions with microbial symbionts (good), pathogens (bad), and complex microbial communities (unknown). Many articles also illustrate how genomics can support translational research by quickly advancing our knowledge of important microbes that have not been widely studied.

 

Click on Next Article or Table of Contents above to view the articles in this Focus Issue. (From the mobile site, go to the MPMI March 2015 issue.)


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pearfriday's comment, June 4, 6:09 AM
Thats amazing...
gobsmackedmumble's comment, July 1, 6:32 AM
Thats striking...
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A secreted Ustilago maydis effector promotes virulence by targeting anthocyanin biosynthesis in maize

A secreted Ustilago maydis effector promotes virulence by targeting anthocyanin biosynthesis in maize | Emerging Research in Plant Cell Biology | Scoop.it

The biotrophic fungus Ustilago maydis causes smut disease in maize with characteristic tumor formation and anthocyanin induction. Here, we show that anthocyanin biosynthesis is induced by the virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with maize protein kinase ZmTTK1. Tin2 masks a ubiquitin–proteasome degradation motif in ZmTTK1, thus stabilizing the active kinase. Active ZmTTK1 controls activation of genes in the anthocyanin biosynthesis pathway. Without Tin2, enhanced lignin biosynthesis is observed in infected tissue and vascular bundles show strong lignification. This is presumably limiting access of fungal hyphae to nutrients needed for massive proliferation. Consistent with this assertion, we observe that maize brown midrib mutants affected in lignin biosynthesis are hypersensitive to U. maydis infection. We speculate that Tin2 rewires metabolites into the anthocyanin pathway to lower their availability for other defense responses.

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PHABULOSA Controls the Quiescent Center-Independent Root Meristem Activities in Arabidopsis thaliana

PHABULOSA Controls the Quiescent Center-Independent Root Meristem Activities in  Arabidopsis thaliana | Emerging Research in Plant Cell Biology | Scoop.it
Author Summary Plant roots are programmed to grow continuously into the soil, searching for nutrients and water. The iterative process of cell division, elongation, and differentiation contributes to root growth. The quiescent center (QC) is known to maintain the root meristem, and thus ensure root growth. In this study, we report a novel aspect of root growth regulation controlled independently of the QC by PHABULOSA (PHB). In shr mutant plants, PHB, which in the meristem is actively restricted to the central region of the stele by SHORTROOT (SHR) via miR165/6 , suppresses root meristem activity leading to root growth arrest. A high concentration of PHB in the stele does this by modulating B-ARR activity through a QC-independent pathway. Accordingly, we observed a significant recovery of root meristem activity and growth in the shr phb double mutant, while the QC remained absent. However, the presence of QC may be required to sustain continuous root growth. On the basis of our results, we propose that SHR maintains root growth via two separate pathways: by modulating PHB levels in the root stele, and by maintaining the QC identity.
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