Emerging Research in Plant Cell Biology
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Two terrific GARNet "Weeding the Gems" blog posts

Two terrific GARNet "Weeding the Gems" blog posts | Emerging Research in Plant Cell Biology | Scoop.it

"Weeding the Gems" (http://blog.garnetcommunity.org.uk/) is a new community blog from GARNet that posts summaries of papers, events and items of general interest to the plant biology community.

 

Their latest two posts look at the fungal pathogen Botrytis cinerea. The first is an overview of a paper from The Plant Cell that looks at high resolution transcriptional responses of Arabidopsis to Botrytis (http://dx.doi.org/10.1105/tpc.112.102046).

 

They follow up with a fun post of a time-lapse video showing what Botrytis does to a strawberry, and a video about how the wine industry sometimes benefits from Botrytis infection - yummy

(http://blog.garnetcommunity.org.uk/botrytis-cinerea-time-lapse/).

 

WtG is an attractive and informative blog, and you can get updates of new posts by following @weedinggems.


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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.
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1,135 Genomes Reveal the Global Pattern of Polymorphism in Arabidopsis thaliana

1,135 Genomes Reveal the Global Pattern of Polymorphism in Arabidopsis thaliana | Emerging Research in Plant Cell Biology | Scoop.it
Arabidopsis thaliana serves as a model organism for the study of fundamental physiological, cellular, and molecular processes. It has also greatly advanced our understanding of intraspecific genome variation. We present a detailed map of variation in 1,135 high-quality re-sequenced natural inbred lines representing the native Eurasian and North African range and recently colonized North America. We identify relict populations that continue to inhabit ancestral habitats, primarily in the Iberian Peninsula. They have mixed with a lineage that has spread to northern latitudes from an unknown glacial refugium and is now found in a much broader spectrum of habitats. Insights into the history of the species and the fine-scale distribution of genetic diversity provide the basis for full exploitation of A. thaliana natural variation through integration of genomes and epigenomes with molecular and non-molecular phenotypes.
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Sequencing of the genus Arabidopsis identifies a complex history of nonbifurcating speciation and abundant trans-specific polymorphism : Nature Genetics : Nature Publishing Group

Sequencing of the genus Arabidopsis identifies a complex history of nonbifurcating speciation and abundant trans-specific polymorphism : Nature Genetics : Nature Publishing Group | Emerging Research in Plant Cell Biology | Scoop.it
Magnus Nordborg and colleagues report a genomic analysis of all 27 known species in the genus Arabidopsis. They find evidence for a complex speciation history that is not accurately reflected by a traditional bifurcating species tree and identify widespread shared polymorphisms between species.
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Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016)

Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016) | Emerging Research in Plant Cell Biology | Scoop.it

Programmed cell death (PCD) is a conserved process among eukaryotes that serves a multitude of functional roles during an organism’s natural life cycle. PCD involves the tightly regulated process of cell death cued by specific spatiotemporal stimuli, which confer survival benefits. In eukaryotes, PCD is an essential process involved in senescence, aging, embryo development, cell differentiation, and immunity. In animal systems, morphologically distinct forms of PCD have been described (Figure 1) [1, 2]. Type I, or apoptotic cell death, is the best understood form of PCD and is defined by cell shrinkage, nuclear condensation and fragmentation, and eventual disintegration of the cell into apoptotic bodies that are digested by phagocytes. Type II cell death is an autophagic process that is induced during nutrient deprivation and chronic stress. Autophagic cell death is characterized by the rupture of the lysosome and subsequent release of toxic chemicals that degrade the cell contents. Unlike type I and type II, type III PCD is distinguished by the swelling of organelles and subsequent rupture of the plasma membrane. A programmed necrosis or necroptosis was initially believed to be an uncontrolled process of necrosis, but has been recently reclassified as type III form of cell death. Finally, pyroptosis is another recently categorized form of cell death that is mediated by caspase-1 activity. Morphologically, pyroptotic cells share characteristics of both apoptosis and necrosis [1]. Noteworthy, necroptosis and pyroptosis are pro-inflammatory forms of PCD activated by microbial infections and diverse environmental stimuli.

 

In plants, PCD is less rigorously classified (Figure 1). One difficulty in distinguishing the forms of PCD in plants and animals comes as a result of the different cellular morphology in plant cells — most notably the presence of the cell wall and chloroplasts. Unlike the plasma membrane, the degradation of the cell wall is not a universal feature of PCD in plants. Additionally, the formation of apoptotic bodies is not observed in plant cells, as there are no circulating phagocytes to engulf them [3]. Instead, plant cells committed to PCD release autolytic compounds stored in the vacuole that degrade cell contents. In these cases, the cell wall may develop perforations for the absorption and recycling of cellular components by neighboring cells. Although not as well characterized as the mitochondria, the chloroplasts have been shown to induce light-dependent PCD through singlet oxygen species (1O2) that may function in parallel to mitochondrial-mediated PCD at an early step in initiating the rupture of the vacuole [3].

 

A specialized form of plant cell death called hypersensitive response (HR) is initiated as a defense response to pathogen infection. HR shares morphological features and molecular mechanisms reminiscent of both pyroptosis and necroptosis [4]. Moreover, HR is unique in that it induces a signaling cascade to propagate immunity in neighboring cells as well as priming distal tissues for potential pathogen challenge, a phenomenon known as systemic acquired resistance [5]. Here we will briefly describe diverse plant disease resistance pathways, early molecular events during pathogen perception, and downstream signaling components. We will thoroughly discuss how pathogens have evolved strategies to circumvent and/or suppress diverse immune responses, in particular plant cell death. While many of these mechanisms involve indirect disabling of upstream immune responses to avoid cell death, direct manipulation of PCD regulators by pathogen effectors has not been extensively explored in the literature, and will be the focal point of this article.


Via Kamoun Lab @ TSL
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Special Issue: Next-generation precision genome engineering and plant biotechnology

Special Issue: Next-generation precision genome engineering and plant biotechnology | Emerging Research in Plant Cell Biology | Scoop.it
In recent history, mutagenesis, selection, and breeding of crop varieties have significantly improved agricultural traits and increased yields, for example, the renowned Green Revolution work on control of plant stature. Early in the 1990s, transgenic technologies were transformative to commercial crop agriculture by adding foreign DNA to improve plant traits. The transgenic methods traditionally used for crop improvement have many limitations, including random insertions, potential silencing, and varied gene expression. Transgenic methods also do not exploit the full potential of the genetic repertoire of the plant species targeted for improvement. Moreover, there remain dogged public concerns on consuming food from transgenic plants, “GMOs,” especially those with genes from distantly related organisms. Nonetheless, crop improvement and basic research have greatly benefitted from targeted modification of plant genomes. In this special issue (SI), which includes eight reviews, two opinion papers, and four original articles, the development of targeted genome editing approaches in higher plants is discussed from various perspectives, including research, intellectual property, regulatory affairs, and consumer acceptance issues.
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PNAS: Rapidly evolving R genes in diverse grass species confer resistance to rice blast disease (2013)

PNAS: Rapidly evolving R genes in diverse grass species confer resistance to rice blast disease (2013) | Emerging Research in Plant Cell Biology | Scoop.it

We show that the genomes of maize, sorghum, and brachypodium contain genes that, when transformed into rice, confer resistance to rice blast disease. The genes are resistance genes (R genes) that encode proteins with nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains (NBS–LRR proteins). By using criteria associated with rapid molecular evolution, we identified three rapidly evolving R-gene families in these species as well as in rice, and transformed a randomly chosen subset of these genes into rice strains known to be sensitive to rice blast disease caused by the fungus Magnaporthe oryzae. The transformed strains were then tested for sensitivity or resistance to 12 diverse strains of M. oryzae. A total of 15 functional blast R genes were identified among 60 NBS–LRR genes cloned from maize, sorghum, and brachypodium; and 13 blast R genes were obtained from 20 NBS–LRR paralogs in rice. These results show that abundant blast R genes occur not only within species but also among species, and that the R genes in the same rapidly evolving gene family can exhibit an effector response that confers resistance to rapidly evolving fungal pathogens. Neither conventional evolutionary conservation nor conventional evolutionary convergence supplies a satisfactory explanation of our findings. We suggest a unique mechanism termed “constrained divergence,” in which R genes and pathogen effectors can follow only limited evolutionary pathways to increase fitness. Our results open avenues for R-gene identification that will help to elucidate R-gene vs. effector mechanisms and may yield new sources of durable pathogen resistance.


Via Kamoun Lab @ TSL
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Pea Plants Show Risk Sensitivity

Pea Plants Show Risk Sensitivity | Emerging Research in Plant Cell Biology | Scoop.it
Sensitivity to variability in resources has been documented in humans, primates, birds, and social insects, but the fit between empirical results and the predictions of risk sensitivity theory (RST), which aims to explain this sensitivity in adaptive terms, is weak [ 1 ]. RST predicts that agents should switch between risk proneness and risk aversion depending on state and circumstances, especially according to the richness of the least variable option [ 2 ]. Unrealistic assumptions about agents’ information processing mechanisms and poor knowledge of the extent to which variability imposes specific selection in nature are strong candidates to explain the gap between theory and data. RST’s rationale also applies to plants, where it has not hitherto been tested. Given the differences between animals’ and plants’ information processing mechanisms, such tests should help unravel the conflicts between theory and data. Measuring root growth allocation by split-root pea plants, we show that they favor variability when mean nutrient levels are low and the opposite when they are high, supporting the most widespread RST prediction. However, the combination of non-linear effects of nitrogen availability at local and systemic levels may explain some of these effects as a consequence of mechanisms not necessarily evolved to cope with variance [ 3, 4 ]. This resembles animal examples in which properties of perception and learning cause risk sensitivity even though they are not risk adaptations [ 5 ].
Jennifer Mach's insight:
This paper has been all over the news-- looking forward to checking it out.
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Trichomes control flower bud shape by linking together young petals

Trichomes control flower bud shape by linking together young petals | Emerging Research in Plant Cell Biology | Scoop.it
Trichomes are widespread in plants and develop from surface cells on different tissues1. They have many forms and functions, from defensive spines to physical barriers that trap layers of air to insulate against desiccation, but there is growing evidence that trichomes can also have developmental roles in regulating flower structure2,3. We report here that the trichomes on petals of cotton, Gossypium hirsutum L., are essential for correct flower bud shape through a mechanical entanglement of the trichomes on adjacent petals that anchor the edges to counter the opposing force generated by asymmetric expansion of overlapping petals. Silencing a master regulator of petal trichomes, GhMYB-MIXTA-Like10 (GhMYBML10), by RNA interference (RNAi) suppressed petal trichome growth and resulted in flower buds forming into abnormal corkscrew shapes that exposed developing anthers and stigmas to desiccation damage. Artificially gluing petal edges together could partially restore correct bud shape and fertility. Such petal ‘Velcro’ is present in other Malvaceae and perhaps more broadly in other plant families, although it is not ubiquitous. This mechanism for physical association between separate organs to regulate flower shape and function is different from the usual organ shape control4 exerted through cell-to-cell communication and differential cell expansion within floral tissues5,6.Trichomes control flower bud shape by linking together young petals
Jennifer Mach's insight:
A mechanical role for trichomes in floral development!
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Fungal Innate Immunity Induced by Bacterial Microbe-Associated Molecular Patterns (MAMPs)

Fungal Innate Immunity Induced by Bacterial Microbe-Associated Molecular Patterns (MAMPs) | Emerging Research in Plant Cell Biology | Scoop.it
Plants and animals detect bacterial presence through Microbe-Associated Molecular Patterns (MAMPs) which induce an innate immune response. The field of fungal–bacterial interaction at the molecular level is still in its infancy and little is known about MAMPs and their detection by fungi. Exposing Fusarium graminearum to bacterial MAMPs led to increased fungal membrane hyperpolarization, a putative defense response, and a range of transcriptional responses. The fungus reacted with a different transcript profile to each of the three tested MAMPs, although a core set of genes related to energy generation, transport, amino acid production, secondary metabolism, and especially iron uptake were detected for all three. Half of the genes related to iron uptake were predicted MirA type transporters that potentially take up bacterial siderophores. These quick responses can be viewed as a preparation for further interactions with beneficial or pathogenic bacteria, and constitute a fungal innate immune response with similarities to those of plants and animals.

Via Francis Martin, Christophe Jacquet
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Zhenchuan Ma's comment, June 2, 8:40 PM
Interesting work!
Jessie Uehling's curator insight, June 5, 8:12 PM
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Nature Microbiology: Fungal pathogenesis: Host modulation every which way (2016)

Nature Microbiology: Fungal pathogenesis: Host modulation every which way (2016) | Emerging Research in Plant Cell Biology | Scoop.it

The plant pathogenic fungus Fusarium oxysporum secretes an effector that is similar to a plant peptide hormone, underscoring the variety of mechanisms that plant pathogens have evolved to tamper with host physiology.

 

Plant pathogens cause devastating diseases of crop plants and threaten food security in an era of continuous population growth. Annual losses due to fungal and oomycete diseases amount to enough food calories to feed at least half a billion people. Understanding how plant pathogens infect and colonize plants should help to develop disease-resistant crops. It appears that plant pathogens are sophisticated manipulators of their hosts. They secrete effector molecules that alter host biological processes in a variety of ways, generally promoting the pathogen lifestyle. A new study by Masachis, Segorbe and colleagues describes a new mechanism by which plant pathogens interfere with plant physiology. They discovered that the root-infecting fungus F. oxysporum secretes a peptide similar to the plant regulatory peptide RALF (rapid alkalinization factor) to induce host tissue alkalinization and enhance plant colonization. This study demonstrates that in addition to secreting classical plant hormones (or mimics thereof), fungi have also evolved functional homologues of plant peptides to alter host cellular processes.


Via Kamoun Lab @ TSL
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Ectomycorrhizal fungal spore bank recovery after a severe forest fire: some like it hot

Ectomycorrhizal fungal spore bank recovery after a severe forest fire: some like it hot | Emerging Research in Plant Cell Biology | Scoop.it
After severe wildfires, pine recovery depends on ectomycorrhizal (ECM) fungal spores surviving and serving as partners for regenerating forest trees. We took advantage of a large, severe natural forest fire that burned our long-term study plots to test the response of ECM fungi to fire. We sampled the ECM spore bank using pine seedling bioassays and high-throughput sequencing before and after the California Rim Fire. We found that ECM spore bank fungi survived the fire and dominated the colonization of in situ and bioassay seedlings, but there were specific fire adapted fungi such as Rhizopogon olivaceotinctus that increased in abundance after the fire. The frequency of ECM fungal species colonizing pre-fire bioassay seedlings, post-fire bioassay seedlings and in situ seedlings were strongly positively correlated. However, fire reduced the ECM spore bank richness by eliminating some of the rare species, and the density of the spore bank was reduced as evidenced by a larger number of soil samples that yielded uncolonized seedlings. Our results show that although there is a reduction in ECM inoculum, the ECM spore bank community largely remains intact, even after a high-intensity fire. We used advanced techniques for data quality control with Illumina and found consistent results among varying methods. Furthermore, simple greenhouse bioassays can be used to determine which fungi will colonize after fires. Similar to plant seed banks, a specific suite of ruderal, spore bank fungi take advantage of open niche space after fires.

Via Francis Martin, Christophe Jacquet
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An effective strategy for reliably isolating heritable and Cas9-free Arabidopsis mutants generated by CRISPR/Cas9-mediated genome editing

An effective strategy for reliably isolating heritable and Cas9-free Arabidopsis mutants generated by CRISPR/Cas9-mediated genome editing | Emerging Research in Plant Cell Biology | Scoop.it
Mutations generated by CRISPR/Cas9 in Arabidopsis are often somatic and are rarely heritable. Isolation of mutations in Cas9-free Arabidopsis plants can ensure stable transmission of the identified mutations to next generations, but the process is laborious and inefficient. Here we present a simple visual screen for Cas9-free T2 seeds, allowing us to quickly obtain Cas9-free Arabidopsis mutants at T2 generation. To demonstrate this in principle, we targeted two sites in the AUXIN BINDING PROTEIN 1 (ABP1) gene, whose function as a membrane-associated auxin receptor has been challenged recently. We obtained many T1 plants with detectable mutations near the target sites, but only a small fraction of T1 plants yielded Cas9-free abp1 mutations at T2 generation. Moreover, the mutations did not segregate in Mendelian fashion at T2 generation. However, mutations identified in the Cas9-free T2 plants were stably transmitted to T3 generation following Mendelian genetics. To further simplify the screening procedure, we simultaneously targeted two sites in ABP1 to generate large deletions, which can be easily identified by a PCR reaction. We successfully generated two abp1 alleles, which contained 1141 bp and 711 bp deletions in the ABP1 gene, respectively. All of the Cas9-free abp1 alleles we generated were stable and heritable. The method described here allows for effectively isolating Cas9-free heritable CRISPR mutants in Arabidopsis.
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Phosphorus: The Underrated Element for Feeding the World: Trends in Plant Science

Phosphorus: The Underrated Element for Feeding the World: Trends in Plant Science | Emerging Research in Plant Cell Biology | Scoop.it
Predictions on the lifetime of phosphate (Pi) reserves usually take into account only the need for crop production. A recent report predicts the global need of chemical Pi fertilizer for sustaining productivity in cropland and grassland. Here we discuss the implications of these predictions for the lifetime of Pi reserves.

Via Christophe Jacquet, Jean-Michel Ané
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TOPOISOMERASE1α Acts through Two Distinct Mechanisms to Regulate Stele and Columella Stem Cell Maintenance

TOPOISOMERASE1α Acts through Two Distinct Mechanisms to Regulate Stele and Columella Stem Cell Maintenance | Emerging Research in Plant Cell Biology | Scoop.it
TOPOISOMERASE1 (TOP1), which releases DNA torsional stress generated during replication through its DNA relaxation activity, plays vital roles in animal and plant development. In Arabidopsis (Arabidopsis thaliana), TOP1 is encoded by two paralogous genes (TOP1α and TOP1β), of which TOP1α displays specific developmental functions that are critical for the maintenance of shoot and floral stem cells. Here, we show that maintenance of two different populations of root stem cells is also dependent on TOP1α-specific developmental functions, which are exerted through two distinct novel mechanisms. In the proximal root meristem, the DNA relaxation activity of TOP1α is critical to ensure genome integrity and survival of stele stem cells (SSCs). Loss of TOP1α function triggers DNA double-strand breaks in S-phase SSCs and results in their death, which can be partially reversed by the replenishment of SSCs mediated by ETHYLENE RESPONSE FACTOR115. In the quiescent center and root cap meristem, TOP1α is epistatic to RETINOBLASTOMA-RELATED (RBR) in the maintenance of undifferentiated state and the number of columella stem cells (CSCs). Loss of TOP1α function in either wild-type or RBR RNAi plants leads to differentiation of CSCs, whereas overexpression of TOP1α mimics and further enhances the effect of RBR reduction that increases the number of CSCs. Taken together, these findings provide important mechanistic insights into understanding stem cell maintenance in plants.

Via Christophe Jacquet
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Testing the Münch hypothesis of long distance phloem transport in plants

Testing the Münch hypothesis of long distance phloem transport in plants | Emerging Research in Plant Cell Biology | Scoop.it

Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.

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Nature Plants: A symbiotic SNARE protein generated by alternative termination of transcription (2016)

Nature Plants: A symbiotic SNARE protein generated by alternative termination of transcription (2016) | Emerging Research in Plant Cell Biology | Scoop.it

Many microbes interact with their hosts across a membrane interface, which is often distinct from existing membranes. Understanding how this interface acquires its identity has significant implications. In the symbiosis between legumes and rhizobia, the symbiosome encases the intracellular bacteria and receives host secretory proteins important for bacterial development. We show that the Medicago truncatula SYNTAXIN 132 (SYP132) gene undergoes alternative cleavage and polyadenylation during transcription, giving rise to two target-membrane soluble NSF attachment protein receptor (t-SNARE) isoforms. One of these isoforms, SYP132A, is induced during the symbiosis, is able to localize to the peribacteroid membrane, and is required for the maturation of symbiosomes into functional forms. The second isoform, SYP132C, has important functions unrelated to symbiosis. The SYP132A sequence is broadly found in flowering plants that form arbuscular mycorrhizal symbiosis, an ancestral mutualism between soil fungi and most land plants. SYP132A silencing severely inhibited arbuscule colonization, indicating that SYP132A is an ancient factor specifying plant–microbe interfaces.


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S-Acylation of the cellulose synthase complex is essential for its plasma membrane localization

S-Acylation of the cellulose synthase complex is essential for its plasma membrane localization | Emerging Research in Plant Cell Biology | Scoop.it
Cellulose synthase is a large, multisubunit machine that “swims” along the plant cell membrane as it spins out cellulose fibers. Kumar et al. show that the cellulose synthase complex is heavily modified through S-acylation. Subsets of the acylation sites were required for the complex to integrate into the plasma membrane. A single functional complex could bear as many as 100 modification sites, potentially changing its biophysical characteristics and helping it to associate with the membrane.

Science , this issue p. [166][1]

[1]: /lookup/doi/10.1126/science.aaf4009
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Current Opinion in Plant Biology: Signals and cues in the evolution of plant–microbe communication (2016)

Current Opinion in Plant Biology: Signals and cues in the evolution of plant–microbe communication (2016) | Emerging Research in Plant Cell Biology | Scoop.it

Communication has played a key role in organismal evolution. If sender and receiver have a shared interest in propagating reliable information, such as when they are kin relatives, then effective communication can bring large fitness benefits. However, interspecific communication (among different species) is more prone to dishonesty. Over the last decade, plants and their microbial root symbionts have become a model system for studying interspecific molecular crosstalk. However, less is known about the evolutionary stability of plant–microbe communication. What prevents partners from hijacking or manipulating information to their own benefit? Here, we focus on communication between arbuscular mycorrhizal fungi and their host plants. We ask how partners use directed signals to convey specific information, and highlight research on the problem of dishonest signaling.


Via Kamoun Lab @ TSL, Jim Alfano
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Revisiting the phosphatidylethanolamine-binding protein (PEBP) gene family reveals cryptic FLOWERING LOCUS T gene homologs in gymnosperms and sheds new light on functional evolution

Revisiting the phosphatidylethanolamine-binding protein (PEBP) gene family reveals cryptic FLOWERING LOCUS T gene homologs in gymnosperms and sheds new light on functional evolution | Emerging Research in Plant Cell Biology | Scoop.it
Angiosperms and gymnosperms are two major groups of extant seed plants. It has been suggested that gymnosperms lack FLOWERING LOCUS T (FT), a key integrator at the core of flowering pathways in angiosperms. Taking advantage of newly released gymnosperm genomes, we revisited the evolutionary history of the plant phosphatidylethanolamine-binding protein (PEBP) gene family through phylogenetic reconstruction. Expression patterns in three gymnosperm taxa and heterologous expression in Arabidopsis were studied to investigate the functions of gymnosperm FT-like and TERMINAL FLOWER 1 (TFL1)-like genes. Phylogenetic reconstruction suggests that an ancient gene duplication predating the divergence of seed plants gave rise to the FT and TFL1 genes. Expression patterns indicate that gymnosperm TFL1-like genes play a role in the reproductive development process, while GymFT1 and GymFT2, the FT-like genes resulting from a duplication event in the common ancestor of gymnosperms, function in both growth rhythm and sexual development pathways. When expressed in Arabidopsis, both spruce FT-like and TFL1-like genes repressed flowering. Our study demonstrates that gymnosperms do have FT-like and TFL1-like genes. Frequent gene and genome duplications contributed significantly to the expansion of the plant PEBP gene family. The expression patterns of gymnosperm PEBP genes provide novel insight into the functional evolution of this gene family.

Via Pierre-Marc Delaux
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Chloroplast FtsZ assembles into a contractible ring via tubulin-like heteropolymerization

Chloroplast FtsZ assembles into a contractible ring via tubulin-like heteropolymerization | Emerging Research in Plant Cell Biology | Scoop.it
Chloroplast division is driven by a ring containing FtsZ1 and FtsZ2 proteins, which originated from bacterial FtsZ, a tubulin-like protein; however, mechanistic details of the chloroplast FtsZ ring remain unclear. Here, we report that FtsZ1 and FtsZ2 can heteropolymerize into a contractible ring ex vivo. Fluorescently labelled FtsZ1 and/or FtsZ2 formed single rings in cells of the yeast Pichia pastoris. Photobleaching experiments indicated that co-assembly of FtsZ1 and FtsZ2 imparts polarity to polymerization. Assembly of FtsZ chimaeras revealed that the protofilaments assemble via heteropolymerization of FtsZ2 and FtsZ1. Contraction of the ring was accompanied by an increase in the filament turnover rate. Our findings suggest that the evolutionary duplication of FtsZ in plants may have increased the mobility and kinetics of FtsZ ring dynamics in chloroplast division. Thus, the gene duplication and heteropolymerization of chloroplast FtsZs may represent convergent evolution with eukaryotic tubulin.
Jennifer Mach's insight:
How FtsZ polymerizes into a contractile ring in chloroplasts-- recapitulated in the yeast Pichia.
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Advancing Crop Transformation in the Era of Genome Editing

Plant transformation has enabled fundamental insights into plant biology and revolutionized commercial agriculture. Unfortunately, for most crops, transformation and regeneration remain arduous even after more than thirty years of technological advances. Genome editing provides new opportunities to enhance crop productivity, but relies on genetic transformation and plant regeneration, which are bottlenecks in the process. Herein we review the state of plant transformation and point to innovations needed to enable genome editing in crops. Plant tissue culture methods need optimization and simplification for efficiency and minimize time in culture. Currently, specialized facilities exist for crop transformation. Single cell and robotic techniques should be developed for high throughput genomic screens. Utilization of plant genes involved in developmental reprogramming, wound response, and/or homologous recombination could boost recovery of transformed plants. Engineering universal Agrobacterium strains and recruitment of other microbes, such as Ensifer or Rhizobium, could facilitate delivery of DNA and proteins into plant cells. Synthetic biology should be employed for de novo design of transformation systems. Genome editing is a potential game-changer in crop genetics when plant transformation systems are optimized.
Jennifer Mach's insight:
We all love CRISPR/Cas and the exciting potential for genome editing-- but what to do for species where it's hard to regenerate a whole plant? Whither tissue culture?
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Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins

Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins | Emerging Research in Plant Cell Biology | Scoop.it
Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins | The auxin-sensitive Aux/IAA transcriptional repressors regulate approximately 35% of the annotated genes in Physcomitrella patens and exhibit complex interactions with both the activating and repressing ARF transcription factors.
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Nuclear-localized cyclic nucleotide–gated channels mediate symbiotic calcium oscillations

Nuclear-localized cyclic nucleotide–gated channels mediate symbiotic calcium oscillations | Emerging Research in Plant Cell Biology | Scoop.it
Plant cell nuclei respond to signals from symbiotic nitrogenfixing rhizobial bacteria or arbuscular mycorrhizal fungi with oscillating Ca2+ release. Charpentier et al. identified a trio of responsible Ca2+ channels in a legume. These channels contain nuclear localization signals and are expressed in root cell nuclear envelopes. The channels function early in the establishment of symbiosis to produce oscillations in Ca2+ release from nuclear stores.

Science , this issue p. [1102][1]

[1]: /lookup/doi/10.1126/science.aae0109
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Protocol: a method to study the direct reprogramming of lateral root primordia to fertile shoots.

Protocol: a method to study the direct reprogramming of lateral root primordia to fertile shoots. | Emerging Research in Plant Cell Biology | Scoop.it
Plant Methods is an open access, peer-reviewed, online journal for the plant research community that encompasses all aspects of technological innovation in the plant sciences.
There is no doubt that we have entered an exciting new era in plant biology. The completion of the Arabidopsis genome sequence, and the rapid progress being made in other plant genomics projects are providing unparalleled opportunities for progress in all areas of plant science. Nevertheless, enormous challenges lie ahead if we are to understand the function of every gene in the genome, and how the individual parts work together to make the whole organism. Achieving these goals will require an unprecedented collaborative effort, combining high-throughput, system-wide technologies with more focused approaches that integrate traditional disciplines such as cell biology, biochemistry and molecular genetics.
Technological innovation is probably the most important catalyst for progress in any scientific discipline. Plant Methods’ goal is to stimulate the development and adoption of new and improved techniques and research tools and, where appropriate, to promote consistency of methodologies for better integration of data from different laboratories.

Via Christophe Jacquet
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Survival trade-offs in plant roots during colonization by closely related beneficial and pathogenic fungi

Survival trade-offs in plant roots during colonization by closely related beneficial and pathogenic fungi | Emerging Research in Plant Cell Biology | Scoop.it
The sessile nature of plants forced them to evolve mechanisms to prioritize their responses to simultaneous stresses, including colonization by microbes or nutrient starvation. Here, we compare the genomes of a beneficial root endophyte, Colletotrichum tofieldiae and its pathogenic relative C. incanum, and examine the transcriptomes of both fungi and their plant host Arabidopsis during phosphate starvation. Although the two species diverged only 8.8 million years ago and have similar gene arsenals, we identify genomic signatures indicative of an evolutionary transition from pathogenic to beneficial lifestyles, including a narrowed repertoire of secreted effector proteins, expanded families of chitin-binding and secondary metabolism-related proteins, and limited activation of pathogenicity-related genes in planta. We show that beneficial responses are prioritized in C. tofieldiae-colonized roots under phosphate-deficient conditions, whereas defense responses are activated under phosphate-sufficient conditions. These immune responses are retained in phosphate-starved roots colonized by pathogenic C. incanum, illustrating the ability of plants to maximize survival in response to conflicting stresses.

Via Stéphane Hacquard, Jean-Michel Ané
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Sequence-specific protein aggregation generates defined protein knockdowns in plants

Protein aggregation is determined by short (5-15 amino acids) aggregation-prone regions (APRs) of the polypeptide sequence that self-associate in a specific manner to form β-structured inclusions. Here, we demonstrate that the sequence specificity of APRs can be exploited to selectively knockdown proteins with different localization and function in plants. Synthetic aggregation-prone peptides derived from the APRs of either the negative regulators of the brassinosteroid (BR) signaling, the glycogen synthase kinase 3/Arabidopsis SHAGGY-like kinases (GSK3/ASKs), or the starch-degrading enzyme α-glucan water dikinase (GWD) were designed. Stable expression of the APRs in Arabidopsis thaliana (Arabidopsis) and Zea mays (maize) induced aggregation of the target proteins, giving rise to plants displaying constitutive BR responses and increased starch content, respectively. Overall, we show that the sequence specificity of APRs can be harnessed to generate aggregation-associated phenotypes in a targeted manner in different subcellular compartments. This study points toward the potential application of induced targeted aggregation as a useful tool to knockdown protein functions in plants and, especially, to generate beneficial traits in crops.
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