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The beet R locus encodes a new cytochrome P450 required for red betalain production

The beet R locus encodes a new cytochrome P450 required for red betalain production | plant cell genetics | Scoop.it

Anthocyanins are red and violet pigments that color flowers, fruits and epidermal tissues in virtually all flowering plants. A single order, Caryophyllales, contains families in which an unrelated family of pigments, the betalains, color tissues normally pigmented by anthocyanins1. Here we show thatCYP76AD1 encoding a novel cytochrome P450 is required to produce the red betacyanin pigments in beets. Gene silencing of CYP76AD1 results in loss of red pigment and production of only yellow betaxanthin pigment. Yellow betalain mutants are complemented by transgenic expression ofCYP76AD1, and an insertion in CYP76AD1 maps to the R locus2, 3 that is responsible for yellow versus red pigmentation. Finally, expression of CYP76AD1 in yeast verifies its position in the betalain biosynthetic pathway. Thus, this cytochrome P450 performs the biosynthetic step that provides the cyclo-DOPA moiety of all red betacyanins. This discovery will contribute to our ability to engineer this simple, nutritionally valuable pathway4 into heterologous species

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Basidiomycete yeasts in the cortex of ascomycete macrolichens

Basidiomycete yeasts in the cortex of ascomycete macrolichens | plant cell genetics | Scoop.it
For over 140 years, lichens have been regarded as a symbiosis between a single fungus, usually an ascomycete, and a photosynthesizing partner. Other fungi have long been known to occur as occasional parasites or endophytes, but the one lichen–one fungus paradigm has seldom been questioned. Here we show that many common lichens are composed of the known ascomycete, the photosynthesizing partner, and, unexpectedly, specific basidiomycete yeasts. These yeasts are embedded in the cortex, and their abundance correlates with previously unexplained variations in phenotype. Basidiomycete lineages maintain close associations with specific lichen species over large geographical distances and have been found on six continents. The structurally important lichen cortex, long treated as a zone of differentiated ascomycete cells, appears to consistently contain two unrelated fungi.
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Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016)

Current Biology: Pathogen Tactics to Manipulate Plant Cell Death (2016) | plant cell genetics | 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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Factors associated with the farmer suicide crisis in India Bt cotton is unlikely to be an important factor

Socioeconomic factors, rather than mental health problems, are associated with farmer suicides, with increased indebtedness playing the predominant role. Available research suggests this has arisen to a greater extent recently, due to an agrarian crisis affecting the most vulnerable farmers. This has multiple manifestations, including a lack of agricultural investment and irrigation improvement, use of cash crops, the increased use of noninstitutional credit sources, and the reduction of trade barriers. Bt cotton is unlikely to be an important factor and no studies reported a significant burden of mental health problems.
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The Cultivar Series

The Cultivar Series | plant cell genetics | Scoop.it
This website showcases the work of Berlin based artist Uli Westphal. His works deal with the way humans perceive, depict and transform the natural world.

Via Saclay Plant Sciences
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The critical role of pre-publication peer review—a case study of glyphosate

This discussion considers the impact of inadequate peer review on an internationally important decision on the safety of a common pesticide. There have been hundreds of articles and essays and conferences on the importance and the problems of pre-publication review, but difficulties with the process are still with us.

Ideally, before publication, a research report submitted to a scientific journal is sent by the editor to one or more experts in the field for review. The author responds to the critiques and the editor(s) decide whether the revised paper is to be published. That ideal may fail if the pre-publication peer review has been less than thorough or the work has been sent to a journal with inadequate or no review. Unfortunately, such outlets do exist. When poor work finds its way into print, it is too often accepted as authoritative. The costs in time, knowledge, and social distress are substantial.

The consequences of insufficiently critiqued publication on an issue of worldwide concern can be expected to draw more attention to the problem: A useful example has been handed the scientific community in the recent Monograph 112 of the International Agency for Research on Cancer (IARC), declaring the herbicide glyphosate to be a category 2A, probable human carcinogen (IARC 2015). This is an internationally visible official decision, and it is founded on flawed publications. (Several of the papers used as authoritative by IARC in Monograph 112 were discussed years ago as examples of defective review (Dost 2008).)
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The shocking consequences of hybrid epigenomes

The shocking consequences of hybrid epigenomes | plant cell genetics | Scoop.it
DNA methylation is perhaps the best-known and best-studied chromatin modification. Occurring primarily at cytosine nucleotides in eukaryotic genomes, methylation is a reversible DNA modification that is linked with epialleles, which are genes that are identical in sequence but differ in methylation status and that are inherited between generations. A recent study by Rigal et al. [1] published in Proceedings of the National Academy of Sciences U S A reported the discovery of novel epialleles in hybrids that formed from crossing mutants that are defective in the maintenance of DNA methylation with wild-type plants, highlighting a potential mechanism by which natural epialleles arise.
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An innate immunity pathway in the moss Physcomitrella patens

MAP kinase (MPK) cascades in Arabidopsis thaliana and other vascular plants are activated by developmental cues, abiotic stress, and pathogen infection. Much less is known of MPK functions in nonvascular land plants such as the moss Physcomitrella patens. Here we provide evidence for a signaling pathway in P. patens required for immunity triggered by pathogen associated molecular patterns (PAMPs). This pathway induces rapid growth inhibition, a novel fluorescence burst, cell wall depositions, and accumulation of defense-related transcripts. Two P. patens MPKs (MPK4a and MPK4b) are phosphorylated and activated in response to PAMPs. This activation in response to the fungal PAMP chitin requires a chitin receptor and one or more MAP kinase kinase kinases and MAP kinase kinases. Knockout lines of MPK4a appear wild type but have increased susceptibility to the pathogenic fungi Botrytis cinerea and Alternaria brassisicola. Both PAMPs and osmotic stress activate some of the same MPKs in Arabidopsis. In contrast, abscisic acid treatment or osmotic stress of P. patens does not activate MPK4a or any other MPK, but activates at least one SnRK2 kinase. Signaling via MPK4a may therefore be specific to immunity, and the moss relies on other pathways to respond to osmotic stress.
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Soy and Breast Cancer: Focus on Angiogenesis

Soy and Breast Cancer: Focus on Angiogenesis | plant cell genetics | Scoop.it
Epidemiological studies have revealed that high consumption of soy products is associated with low incidences of hormone-dependent cancers, including breast and prostate cancer. Soybeans contain large amounts of isoflavones, such as the genistein and daidzain. Previously, it has been demonstrated that genistein, one of the predominant soy isoflavones, can inhibit several steps involved in carcinogenesis. It is suggested that genistein possesses pleiotropic molecular mechanisms of action including inhibition of tyrosine kinases, DNA topoisomerase II, 5α-reductase, galectin-induced G2/M arrest, protein histidine kinase, and cyclin-dependent kinases, modulation of different signaling pathways associated with the growth of cancer cells (e.g., NF-κB, Akt, MAPK), etc. Moreover, genistein is also a potent inhibitor of angiogenesis. Uncontrolled angiogenesis is considered as a key step in cancer growth, invasion, and metastasis. Genistein was found to inhibit angiogenesis through regulation of multiple pathways, such as regulation of VEGF, MMPs, EGFR expressions and NF-κB, PI3-K/Akt, ERK1/2 signaling pathways, thereby causing strong antiangiogenic effects. This review focuses on the antiangiogenic properties of soy isoflavonoids and examines their possible underlying mechanisms.
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A Transcriptome Atlas of Physcomitrella patens Provides Insights into the Evolution and Development of Land Plants: Molecular Plant

A Transcriptome Atlas of Physcomitrella patens Provides Insights into the Evolution and Development of Land Plants: Molecular Plant | plant cell genetics | Scoop.it
Identifying the genetic mechanisms that underpin the evolution of new organ and tissue systems is an aim of evolutionary developmental biology. Comparative functional genetic studies between angiosperms and bryophytes can define those genetic changes that were responsible for developmental innovations. Here, we report the generation of a transcriptome atlas covering most phases in the life cycle of the model bryophyte Physcomitrella patens, including detailed sporophyte developmental progression. We identified a comprehensive set of sporophyte-specific transcription factors, and found that many of these genes have homologs in angiosperms that function in developmental processes such as flowering and shoot branching. Deletion of the PpTCP5 transcription factor results in development of supernumerary sporangia attached to a single seta, suggesting that it negatively regulates branching in the moss sporophyte. Given that TCP genes repress branching in angiosperms, we suggest that this activity is ancient. Finally, comparison of P. patens and Arabidopsis thaliana transcriptomes led us to the identification of a conserved core of transcription factors expressed in tip-growing cells. We identified modifications in the expression patterns of these genes that could account for developmental differences between P. patens tip-growing cells and A. thaliana pollen tubes and root hairs.
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Between China and South Asia: A Middle Asian corridor of crop dispersal and agricultural innovation in the Bronze Age

Between China and South Asia: A Middle Asian corridor of crop dispersal and agricultural innovation in the Bronze Age | plant cell genetics | Scoop.it
The period from the late third millennium BC to the start of the first millennium AD witnesses the first steps towards food globalization in which a significant number of important crops and animals, independently domesticated within China, India, Africa and West Asia, traversed Central Asia greatly increasing Eurasian agricultural diversity. This paper utilizes an archaeobotanical database (AsCAD), to explore evidence for these crop translocations along southern and northern routes of interaction between east and west. To begin, crop translocations from the Near East across India and Central Asia are examined for wheat (Triticum aestivum) and barley (Hordeum vulgare) from the eighth to the second millennia BC when they reach China. The case of pulses and flax (Linum usitatissimum) that only complete this journey in Han times (206 BC–AD 220), often never fully adopted, is also addressed. The discussion then turns to the Chinese millets, Panicum miliaceum and Setaria italica, peaches (Amygdalus persica) and apricots (Armeniaca vulgaris), tracing their movement from the fifth millennium to the second millennium BC when the Panicum miliaceum reaches Europe and Setaria italica Northern India, with peaches and apricots present in Kashmir and Swat. Finally, the translocation of japonica rice from China to India that gave rise to indica rice is considered, possibly dating to the second millennium BC. The routes these crops travelled include those to the north via the Inner Asia Mountain Corridor, across Middle Asia, where there is good evidence for wheat, barley and the Chinese millets. The case for japonica rice, apricots and peaches is less clear, and the northern route is contrasted with that through northeast India, Tibet and west China. Not all these journeys were synchronous, and this paper highlights the selective long-distance transport of crops as an alternative to demic-diffusion of farmers with a defined crop package.

Via Dorian Q Fuller, Luigi Guarino
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Dorian Q Fuller's curator insight, June 15, 8:50 AM
An updated treatment of the wider archaeological context of agricultural interchanges between East, West and South within which the hybrid origins of indica rice occurred.
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Scientists discover oldest plant root stem cells

Scientists discover oldest plant root stem cells | plant cell genetics | Scoop.it
Scientists at Oxford University have discovered the oldest known population of plant root stem cells in a 320 million-year-old fossil.
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New developments in engineering plant metabolic pathways

New developments in engineering plant metabolic pathways | plant cell genetics | Scoop.it
Plants contain countless metabolic pathways that are responsible for the biosynthesis of complex metabolites. Armed with new tools in sequencing and bioinformatics, the genes that encode these plant biosynthetic pathways have become easier to discover, putting us in an excellent position to fully harness the wealth of compounds and biocatalysts (enzymes) that plants provide. For overproduction and isolation of high-value plant-derived chemicals, plant pathways can be reconstituted in heterologous hosts. Alternatively, plant pathways can be modified in the native producer to confer new properties to the plant, such as better biofuel production or enhanced nutritional value. This perspective highlights a range of examples that demonstrate how the metabolic pathways of plants can be successfully harnessed with a variety of metabolic engineering approaches.
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Climate-smart soils : Nature : Nature Publishing Group

Climate-smart soils : Nature : Nature Publishing Group | plant cell genetics | Scoop.it
Soils are integral to the function of all terrestrial ecosystems and to food and fibre production. An overlooked aspect of soils is their potential to mitigate greenhouse gas emissions. Although proven practices exist, the implementation of soil-based greenhouse gas mitigation activities are at an early stage and accurately quantifying emissions and reductions remains a substantial challenge. Emerging research and information technology developments provide the potential for a broader inclusion of soils in greenhouse gas policies. Here we highlight ‘state of the art’ soil greenhouse gas research, summarize mitigation practices and potentials, identify gaps in data and understanding and suggest ways to close such gaps through new research, technology and collaboration.
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Heterogeneity of cellular circadian clocks in intact plants and its correction under light-dark cycles

Heterogeneity of cellular circadian clocks in intact plants and its correction under light-dark cycles | plant cell genetics | Scoop.it
Recent advances in single-cell analysis have revealed the stochasticity and nongenetic heterogeneity inherent to cellular processes. However, our knowledge of the actual cellular behaviors in a living multicellular organism is still limited. By using a single-cell bioluminescence imaging technique on duckweed, Lemna gibba , we demonstrate that, under constant conditions, cells in the intact plant work as individual circadian clocks that oscillate with their own frequencies and respond independently to external stimuli. Quantitative analysis uncovered the heterogeneity and instability of cellular clocks and partial synchronization between neighboring cells. Furthermore, we found that cellular clocks in the plant body under light-dark cycles showed a centrifugal phase pattern in which the effect of cell-to-cell heterogeneity in period lengths was almost masked. The inherent heterogeneity in the properties of cellular clocks observed under constant conditions is corrected under light-dark cycles to coordinate the daily rhythms of the plant body. These findings provide a novel perspective of spatiotemporal architectures in the plant circadian system.
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Nature News: Bacterial tricks for turning plants into zombies (2014)

Nature News: Bacterial tricks for turning plants into zombies  (2014) | plant cell genetics | Scoop.it

Many parasites commandeer the bodies of their hosts in order to spread. Examples of this include horsehair worms that reach water by forcing their cricket hosts to drown themselves, and liver flukes that drive infected ants to climb blades of grass, where cows can eat the insects, and so the flukes. But parasites can turn plants into zombies, too — and a team of scientists from the John Innes Centre in Norwich, UK, has now discovered how they do it.


When plants are infected by parasitic bacteria called phytoplasmas, their flowers turn into leafy shoots, their petals turn green and they develop a mass of shoots called ‘witches’ brooms’. This transformation sterilizes the plant, while attracting the sap-sucking insects that carry the bacteria to new hosts. “The plant appears alive, but it’s only there for the good of the pathogen,” says plant pathologist Saskia Hogenhout from the John Innes Centre in Norwich, UK. “In an evolutionary sense, the plant is dead and will not produce offspring.” “Many might baulk at the concept of a zombie plant because the idea of plants behaving is strange,” says David Hughes, a parasitologist at Pennsylvania State University in University Park. “But they do, and since they do, why wouldn't parasites have evolved to take over their behaviour, as they do for ants and crickets?”


Via Kamoun Lab @ TSL
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Genomic analysis of 6,000-year-old cultivated grain illuminates the domestication history of barley

Genomic analysis of 6,000-year-old cultivated grain illuminates the domestication history of barley | plant cell genetics | Scoop.it
The cereal grass barley was domesticated about 10,000 years before the present in the Fertile Crescent and became a founder crop of Neolithic agriculture1. Here we report the genome sequences of five 6,000-year-old barley grains excavated at a cave in the Judean Desert close to the Dead Sea. Comparison to whole-exome sequence data from a diversity panel of present-day barley accessions showed the close affinity of ancient samples to extant landraces from the Southern Levant and Egypt, consistent with a proposed origin of domesticated barley in the Upper Jordan Valley. Our findings suggest that barley landraces grown in present-day Israel have not experienced major lineage turnover over the past six millennia, although there is evidence for gene flow between cultivated and sympatric wild populations. We demonstrate the usefulness of ancient genomes from desiccated archaeobotanical remains in informing research into the origin, early domestication and subsequent migration of crop species.
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Copper-induced structural conversion templates prion protein oligomerization and neurotoxicity

Copper-induced structural conversion templates prion protein oligomerization and neurotoxicity | plant cell genetics | Scoop.it
Prion protein (PrP) misfolding and oligomerization are key pathogenic events in prion disease. Copper exposure has been linked to prion pathogenesis; however, its mechanistic basis is unknown. We resolve, with single-molecule precision, the molecular mechanism of Cu2+-induced misfolding of PrP under physiological conditions. We also demonstrate that misfolded PrPs serve as seeds for templated formation of aggregates, which mediate inflammation and degeneration of neuronal tissue. Using a single-molecule fluorescence assay, we demonstrate that Cu2+ induces PrP monomers to misfold before oligomer assembly; the disordered amino-terminal region mediates this structural change. Single-molecule force spectroscopy measurements show that the misfolded monomers have a 900-fold higher binding affinity compared to the native isoform, which promotes their oligomerization. Real-time quaking-induced conversion demonstrates that misfolded PrPs serve as seeds that template amyloid formation. Finally, organotypic slice cultures show that misfolded PrPs mediate inflammation and degeneration of neuronal tissue. Our study establishes a direct link, at the molecular level, between copper exposure and PrP neurotoxicity.
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CRISPR-Cas9 mediated efficient directed mutagenesis and RAD51-dependent and -independent gene targeting in the moss Physcomitrella patens

CRISPR-Cas9 mediated efficient directed mutagenesis and RAD51-dependent and -independent gene targeting in the moss Physcomitrella patens | plant cell genetics | Scoop.it
The ability to address the CRISPR-Cas9 nuclease complex to any target DNA using customizable single guide RNAs has now permitted genome engineering in many species. Here, we report its first successful use in a non-vascular plant, the moss Physcomitrella patens. Single guide RNAs (sgRNAs) were designed to target an endogenous reporter gene, PpAPT, whose inactivation confers resistance to 2-fluoroadenine. Transformation of moss protoplasts with these sgRNAs and the Cas9 coding sequence from Streptococcus pyogenes triggered mutagenesis at the PpAPT target in about 2% of the regenerated plants. Mainly deletions were observed, most of them resulting from alternative end joining (alt-EJ)-driven repair. We further demonstrate that, in the presence of a donor DNA sharing sequence homology with the PpAPT gene, most transgene integration events occur by homology-driven repair (HDR) at the target locus, but also that Cas9-induced double-strand breaks are repaired with almost equal frequencies by mutagenic illegitimate recombination. Finally, we establish that a significant fraction of HDR-mediated gene targeting events (30%) is still possible in the absence of PpRAD51 protein, indicating that CRISPR-induced HDR is only partially mediated by the classical homologous recombination (HR) pathway.
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Evolutionary Conservation of Xylan Biosynthetic Genes in Selaginella moellendorffii and Physcomitrella patens

Evolutionary Conservation of Xylan Biosynthetic Genes in Selaginella moellendorffii and Physcomitrella patens | plant cell genetics | Scoop.it
Xylan is a major cross-linking hemicellulose in secondary walls of vascular tissues, and the recruitment of xylan as a secondary wall component was suggested to be a pivotal event for the evolution of vascular tissues. To decipher the evolution of xylan structure and xylan biosynthetic genes, we analyzed xylan substitution patterns and characterized genes mediating methylation of glucuronic acid (GlcA) side chains in xylan of the model seedless vascular plant, Selaginella moellendorffii, and investigated GT43 genes from S. moellendorffii and the model non-vascular plant, Physcomitrella patens, for their roles in xylan biosynthesis. Using nuclear magentic resonance spectroscopy, we have demonstrated that S. moellendorffii xylan consists of β-1,4-linked xylosyl residues subsituted solely with methylated GlcA residues and that xylans from both S. moellendorffii and P. patens are acetylated at O-2 and O-3. To investigate genes responsible for GlcA methylation of xylan, we identified two DUF579 genes in the S. moellendorffii genome and showed that one of them, SmGXM, encodes a glucuronoxylan methyltransferase capable of adding the methyl group onto the GlcA side chain of xylooligomers. Furthermore, we revealed that the two GT43 genes in S. moellendorffii, SmGT43A and SmGT43B, are functional orthologs of the Arabidopsis xylan backbone biosynthetic genes IRX9 and IRX14, respectively, indicating the evolutionary conservation of the involvement of two functionally non-redundant groups of GT43 genes in xylan backbone biosynthesis between seedless and seed vascular plants. Among the five GT43 genes in P. patens, PpGT43A was found to be a functional ortholog of Arabidopsis IRX9, suggesting that the recruitment of GT43 genes in xylan backbone biosynthesis occurred when non-vascular plants appeared on land.
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Moss Chloroplasts are Surrounded by a Peptidoglycan Wall Containing D-Amino Acids

It is believed that the plastids in green plants lost peptidoglycan (i.e., a bacterial cell wall containing D-amino acids) during their evolution from an endosymbiotic cyanobacterium. Although wall-like structures could not be detected in the plastids of green plants, the moss Physcomitrella patens has the genes required to generate peptidoglycan (Mur genes), and knocking out these genes causes defects in chloroplast division. Here, we generated P. patens knockout lines (∆Pp-ddl) for a homolog of the bacterial peptidoglycan-synthetic gene encoding D-Ala:D-Ala ligase. ∆Pp-ddl had a macrochloroplast phenotype, similar to other Mur knockout lines. The addition of D-Ala-D-Ala (DA-DA) to the medium suppressed the appearance of giant chloroplasts in ∆Pp-ddl, but the addition of L-Ala-L-Ala (LA-LA), DA-LA, LA-DA or D-Ala, did not. Recently, a metabolic method for labeling bacterial peptidoglycan was established using ethynyl-DA-DA (EDA-DA) and click chemistry to attach an azide-modified fluorophore to the ethynyl group. The ∆Pp-ddl line complemented with EDA-DA showed that moss chloroplasts are completely surrounded by peptidoglycan. Our findings strongly suggest that the moss plastids have a peptidoglycan wall containing D-amino acids. By contrast, no plastid phenotypes were observed in the T-DNA tagged ddl mutant lines of Arabidopsis thaliana.
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Continuous evolution of Bacillus thuringiensis toxins overcomes insect resistance : Nature : Nature Publishing Group

Continuous evolution of Bacillus thuringiensis toxins overcomes insect resistance : Nature : Nature Publishing Group | plant cell genetics | Scoop.it
The Bacillus thuringiensis δ-endotoxins (Bt toxins) are widely used insecticidal proteins in engineered crops that provide agricultural, economic, and environmental benefits. The development of insect resistance to Bt toxins endangers their long-term effectiveness. Here we have developed a phage-assisted continuous evolution selection that rapidly evolves high-affinity protein–protein interactions, and applied this system to evolve variants of the Bt toxin Cry1Ac that bind a cadherin-like receptor from the insect pest Trichoplusia ni (TnCAD) that is not natively bound by wild-type Cry1Ac. The resulting evolved Cry1Ac variants bind TnCAD with high affinity (dissociation constant Kd = 11–41 nM), kill TnCAD-expressing insect cells that are not susceptible to wild-type Cry1Ac, and kill Cry1Ac-resistant T. ni insects up to 335-fold more potently than wild-type Cry1Ac. Our findings establish that the evolution of Bt toxins with novel insect cell receptor affinity can overcome insect Bt toxin resistance and confer lethality approaching that of the wild-type Bt toxin against non-resistant insects.
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A new synthetic biology approach allows transfer of an entire metabolic pathway from a medicinal plant to a biomass crop

A new synthetic biology approach allows transfer of an entire metabolic pathway from a medicinal plant to a biomass crop | plant cell genetics | Scoop.it
A new synthetic biology approach allows transfer of an entire metabolic pathway from a medicinal plant to a biomass crop | A combination of chloroplast transformation with nuclear transformation and large-scale metabolic screening of supertransformed plant lines has enabled an entire biochemical pathway to be transferred from a medicinal plant to a high-biomass crop.
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An innate immunity pathway in the moss Physcomitrella patens

MAP kinase (MPK) cascades in Arabidopsis thaliana and other vascular plants are activated by developmental cues, abiotic stress, and pathogen infection. Much less is known of MPK functions in nonvascular land plants such as the moss Physcomitrella patens. Here we provide evidence for a signaling pathway in P. patens required for immunity triggered by pathogen associated molecular patterns (PAMPs). This pathway induces rapid growth inhibition, a novel fluorescence burst, cell wall depositions, and accumulation of defense-related transcripts. Two P. patens MPKs (MPK4a and MPK4b) are phosphorylated and activated in response to PAMPs. This activation in response to the fungal PAMP chitin requires a chitin receptor and one or more MAP kinase kinase kinases and MAP kinase kinases. Knockout lines of MPK4a appear wild type but have increased susceptibility to the pathogenic fungi Botrytis cinerea and Alternaria brassisicola. Both PAMPs and osmotic stress activate some of the same MPKs in Arabidopsis. In contrast, abscisic acid treatment or osmotic stress of P. patens does not activate MPK4a or any other MPK, but activates at least one SnRK2 kinase. Signaling via MPK4a may therefore be specific to immunity, and the moss relies on other pathways to respond to osmotic stress.
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Holophytochrome-Interacting Proteins in Physcomitrella: Putative Actors in Phytochrome Cytoplasmic Signaling

Holophytochrome-Interacting Proteins in Physcomitrella: Putative Actors in Phytochrome Cytoplasmic Signaling | plant cell genetics | Scoop.it
Phytochromes are the principle photoreceptors in light-regulated plant development, primarily acting via translocation of the light-activated photoreceptor into the nucleus and subsequent gene regulation. However, several independent lines of evidence indicate unambiguously that an additional cytoplasmic signaling mechanism must exist. Directional responses in filament tip cells of the moss Physcomitrella patens are steered by phy4 which has been shown to interact physically with the blue light receptor phototropin at the plasma membrane. This complex might perceive and transduce vectorial information leading to cytoskeleton reorganization and finally a directional growth response. We developed yeast two-hybrid procedures using photochemically functional, full-length phy4 as bait in Physcomitrella cDNA library screens and growth assays under different light conditions, revealing Pfr-dependent interactions possibly associated with phytochrome cytoplasmic signaling. Candidate proteins were then expressed in planta with fluorescent protein tags to determine their intracellular localization in darkness and red light. Of 14 candidates, 12 were confirmed to interact with phy4 in planta using bimolecular fluorescence complementation. We also used database information to study their expression patterns relative to those of phy4. We discuss the likely functional characteristics of these holophytochrome-interacting proteins (HIP’s) and their possible roles in signaling.
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Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE (ANR), a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE (ANR), a regulator of ABA responses unique to basal land plants and required for desiccation tolerance | plant cell genetics | Scoop.it
The anatomically simple plants that first colonised land must have acquired molecular and biochemical adaptations to drought stress. Abscisic acid (ABA) coordinates responses leading to desiccation tolerance in all land plants. We identified ABA non-responsive mutants in the model bryophyte Physcomitrella patens and genotyped a segregating population to map and identify the ABA NON-RESPONSIVE (ANR) gene encoding a modular protein kinase comprising an N-terminal PAS domain, a central EDR domain and a C-terminal MAPKKK-like domain. anr mutants fail to accumulate dehydration tolerance-associated gene products in response to drought, ABA or osmotic stress, and do not acquire ABA-dependent desiccation tolerance. The crystal structure of the PAS domain, determined to 1.7Å resolution, shows a conserved PAS-fold that dimerises through a weak dimerization interface. Targeted mutagenesis of a conserved tryptophan residue within the PAS domain generates plants with ABA non-responsive growth and strongly attenuated ABA-responsive gene expression, whereas deleting this domain retains a fully ABA-responsive phenotype. ANR orthologs are found in early-diverging land plant lineages and aquatic algae, but are absent from more recently diverged vascular plants. We propose that ANR genes represent an ancestral adaptation that enabled drought-stress survival of the first terrestrial colonisers, but were lost during land plant evolution.
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