plant cell genetics
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Dominant resistance to Bt cotton and minor cross-resistance to Bt toxin Cry2Ab in cotton bollworm from China - Jin - 2013 - Evolutionary Applications - Wiley Online Library

Dominant resistance to Bt cotton and minor cross-resistance to Bt toxin Cry2Ab in cotton bollworm from China - Jin - 2013 - Evolutionary Applications - Wiley Online Library | plant cell genetics | Scoop.it

Evolution of resistance by insect pests threatens the long-term benefits of transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt). Previous work has detected increases in the frequency of resistance to Bt toxin Cry1Ac in populations of cotton bollworm, Helicoverpa armigera, from northern China where Bt cotton producing Cry1Ac has been grown extensively for more than a decade. Confirming that trend, we report evidence from 2011 showing that the percentage of individuals resistant to a diagnostic concentration of Cry1Ac was significantly higher in two populations from different provinces of northern China (1.4% and 2.3%) compared with previously tested susceptible field populations (0%). We isolated two resistant strains: one from each of the two field-selected populations. Relative to a susceptible strain, the two strains had 460- and 1200-fold resistance to Cry1Ac, respectively. Both strains had dominant resistance to a diagnostic concentration of Cry1Ac in diet and to Bt cotton leaves containing Cry1Ac. Both strains had low, but significant cross-resistance to Cry2Ab (4.2- and 5.9-fold), which is used widely as the second toxin in two-toxin Bt cotton. Compared with resistance in other strains of H. armigera, the resistance in the two strains characterized here may be especially difficult to suppress.

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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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Néonicotinoïdes : pour la fin des outrances

Néonicotinoïdes : pour la fin des outrances | plant cell genetics | Scoop.it

Via ForumPhyto
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ForumPhyto's curator insight, May 12, 11:43 AM

Autour d'un article de Stéphane Foucart dans Le Monde.
A partir des tweets de @AEGRW et d'un article de Wackes Seppi

Sylvain Rotillon's curator insight, May 12, 4:44 PM

Comme trop souvent, forum phyto dénonce ce qu'ils pratiquent, à savoir une position de lobby. C'est dommage car les contrepoints développés pourraient enrichir le débat.

congruence-RSO's curator insight, May 12, 5:45 PM
ForumPhyto est un regroupement de professionnels du monde agricole qui travaillent ensemble à développer une protection des plantes assumée, responsable et durable sur les fruits, légumes et pommes de terre.
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Gene-edited CRISPR mushroom escapes US regulation

Gene-edited CRISPR mushroom escapes US regulation | plant cell genetics | Scoop.it
A fungus engineered with the CRISPR–Cas9 technique can be cultivated and sold without further oversight.
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Light-driven oxidation of polysaccharides by photosynthetic pigments and a metalloenzyme

Light-driven oxidation of polysaccharides by photosynthetic pigments and a metalloenzyme | plant cell genetics | Scoop.it
Oxidative processes are essential for the degradation of plant biomass. A class of powerful and widely distributed oxidative enzymes, the lytic polysaccharide monooxygenases (LPMOs), oxidize the most recalcitrant polysaccharides and require extracellular electron donors. Here we investigated the effect of using excited photosynthetic pigments as electron donors. LPMOs combined with pigments and reducing agents were exposed to light, which resulted in a never before seen 100-fold increase in catalytic activity. In addition, LPMO substrate specificity was broadened to include both cellulose and hemicellulose. LPMO enzymes and pigment derivatives common in the environment of plant-degrading organisms thus form a highly reactive and stable light-driven system increasing the turnover rate and versatility of LPMOs. This light-driven system may find applications in biotechnology and chemical processing.
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Macro-Process of Past Plant Subsistence from the Upper Paleolithic to Middle Neolithic in China: A Quantitative Analysis of Multi-Archaeobotanical Data

Macro-Process of Past Plant Subsistence from the Upper Paleolithic to Middle Neolithic in China: A Quantitative Analysis of Multi-Archaeobotanical Data | plant cell genetics | Scoop.it
Detailed studies of the long-term development of plant use strategies indicate that plant subsistence patterns have noticeably changed since the Upper Paleolithic, when humans underwent a transitional process from foraging to agriculture. This transition was best recorded in west Asia; however, information about how plant subsistence changed during this transition remains limited in China. This lack of information is mainly due to a limited availability of sufficiently large, quantified archaeobotanical datasets and a paucity of related synthetic analyses. Here, we present a compilation of extensive archaeobotanical data derived from interdisciplinary approaches, and use quantitative analysis methods to reconstruct past plant use from the Upper Paleolithic to Middle Neolithic in China. Our results show that intentional exploitation for certain targeted plants, particularly grass seeds, may be traced back to about 30,000 years ago during the Upper Paleolithic. Subsequently, the gathering of wild plants dominated the subsistence system; however, this practice gradually diminished in dominance until about 6~5 ka cal BP during the Middle Neolithic. At this point, farming based on the domestication of cereals became the major subsistence practice. Interestingly, differences in plant use strategies were detected between north and south China, with respect to (1) the proportion of certain plant taxa in assemblages, (2) the domestication rate of cereals, and (3) the type of plant subsistence practiced after the establishment of full farming. In conclusion, the transition from foraging to rice and millet agriculture in China was a slow and long-term process spanning 10s of 1000s of years, which may be analogous to the developmental paths of wheat and barley farming in west Asia.
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Reconsidering plant memory: Intersections between stress recovery, RNA turnover, and epigenetics

Reconsidering plant memory: Intersections between stress recovery, RNA turnover, and epigenetics | plant cell genetics | Scoop.it
Plants grow in dynamic environments where they can be exposed to a multitude of stressful factors, all of which affect their development, yield, and, ultimately, reproductive success. Plants are adept at rapidly acclimating to stressful conditions and are able to further fortify their defenses by retaining memories of stress to enable stronger or more rapid responses should an environmental perturbation recur. Indeed, one mechanism that is often evoked regarding environmental memories is epigenetics. Yet, there are relatively few examples of such memories; neither is there a clear understanding of their duration, considering the plethora of stresses in nature. We propose that this field would benefit from investigations into the processes and mechanisms enabling recovery from stress. An understanding of stress recovery could provide fresh insights into when, how, and why environmental memories are created and regulated. Stress memories may be maladaptive, hindering recovery and affecting development and potential yield. In some circumstances, it may be advantageous for plants to learn to forget. Accordingly, the recovery process entails a balancing act between resetting and memory formation. During recovery, RNA metabolism, posttranscriptional gene silencing, and RNA-directed DNA methylation have the potential to play key roles in resetting the epigenome and transcriptome and in altering memory. Exploration of this emerging area of research is becoming ever more tractable with advances in genomics, phenomics, and high-throughput sequencing methodology that will enable unprecedented profiling of high-resolution stress recovery time series experiments and sampling of large natural populations.
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EU decision process hinders use of genetically modified trees - VIB (2016)

EU decision process hinders use of genetically modified trees - VIB (2016) | plant cell genetics | Scoop.it

Just like other crops, trees can also be genetically modified in order to introduce new, useful characteristics. Although such trees offer many socio-economic and environmental benefits, complex and unpredictable EU procedures are hindering their introduction to the market. This is the conclusion reached by researchers in a joint text drawn up as part of a European Cooperation in Science and Technology (COST) project about genetically modified trees. The researchers state that Europe is lagging behind in worldwide GM developments and call for a more scientifically substantiated decision process... 

 

Genetically modified trees can be used as an efficient raw material for renewable products or bioenergy, which could in turn promote the transition to a sustainable, CO2-neutral economy. However, Europe imposes a comprehensive risk assessment and authorization procedure on the development and use of genetically modified crops... “It’s also difficult to predict exactly how detailed the risk analyses need to be. This all means that the risk-analysis process for GM trees in Europe demands a huge amount of time and money. More clarity on the data required and the use of predictive models is needed.”

The European decision process is not only complex, but also unpredictable. After the risk analysis and a scientific conclusion from EFSA, it is still by no means certain that a European approval will follow. The fact that individual EU Member States can restrict or prohibit the cultivation of GMOs on their territory for reasons having nothing to do with substantiated risks further increases this uncertainty... “This is in sharp contrast to the introduction of conventionally cultivated, non-European trees and other cultivated crops. Although these also interact differently with their environment, a prior risk analysis is not required for this.”

Genetically modified poplars are already being planted in China and it looks like the green light will also be given in North and South America... “Just like with other GM crops, the commercial developments in the field of GM trees are taking place outside Europe. The question is whether that can be scientifically substantiated. After all, more than twenty years of experiments and commercial application have shown that genetic modification poses no inherent risks. There is no reason to assume trees would be different. Europe should learn from the experience we have built up with GM technology and base its decisions more on scientific facts. Today the decision process is politicized and dogmatic and the environment itself could end up being the biggest victim of this.” 

 

http://www.vib.be/en/news/Pages/EU-regulations-impede-market-introduction-GM-forest-trees.aspx

 

Original article: http://dx.doi.org/10.1016/j.tplants.2016.01.015

 


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The dope on l-DOPA formation for betalain pigments - Schwinn - 2016 - New Phytologist - Wiley Online Library

The dope on l-DOPA formation for betalain pigments - Schwinn - 2016 - New Phytologist - Wiley Online Library | plant cell genetics | Scoop.it
Betalains are remarkable pigments that have long intrigued both plant biologists and chemists. In plants these metabolites impart bright yellow to violet pigmentation to a variety of organs (Fig. 1). They occur only in the core Caryophyllales where in most of the families they replace anthocyanin pigments (Clement et al., 1994; Brockington et al., 2015), evolutionarily older and structurally unrelated compounds that are generally the basis for red to blue colours in plants. The final steps in betalain formation are spontaneous, and the synthesis of their core moieties involves only a few enzymatic steps centred on the production and conversion of l-3,4-dihydroxyphenylalanine (l-DOPA) (Strack et al., 2003). Despite much scientific scrutiny and the apparent relative lack of pathway complexity, progress in identifying the genes involved in the pathway has been slow, preventing the development of a depth of knowledge on betalains to match that for the anthocyanins. However, since the landmark identification of the first biosynthetic gene (Christinet et al., 2004), momentum has grown with the identification of genes for other biosynthetic steps (Hatlestad et al., 2012; Gandía-Herrero & García-Carmona, 2013) and pathway regulation (Hatlestad et al., 2015). Now, in this issue of New Phytologist, Polturak et al. (pp. 269–283) resolve a longstanding puzzle of the pathway: the formation of l-DOPA, the last of the key enzymatic steps to be elucidated. Moreover, as many plants are likely to be deficient in l-DOPA, a major block to the molecular engineering of the pathway has been overcome. The authors dramatically demonstrate this with betalain production in several species of the anthocyanin family Solanaceae. These advances broaden the scope of the questions that can be answered about betalain production and function and open up the biotechnological possibilities.
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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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In vivo assembly of DNA-fragments in the moss, Physcomitrella patens

In vivo assembly of DNA-fragments in the moss, Physcomitrella patens | plant cell genetics | Scoop.it
Direct assembly of multiple linear DNA fragments via homologous recombination, a phenomenon known as in vivo assembly or transformation associated recombination, is used in biotechnology to assemble DNA constructs ranging in size from a few kilobases to full synthetic microbial genomes. It has also enabled the complete replacement of eukaryotic chromosomes with heterologous DNA. The moss Physcomitrella patens, a non-vascular and spore producing land plant (Bryophyte), has a well-established capacity for homologous recombination. Here, we demonstrate the in vivo assembly of multiple DNA fragments in P. patens with three examples of effective genome editing: we (i) efficiently deleted a genomic locus for diterpenoid metabolism yielding a biosynthetic knockout, (ii) introduced a salt inducible promoter, and (iii) re-routed endogenous metabolism into the formation of amorphadiene, a precursor of high-value therapeutics. These proof-of-principle experiments pave the way for more complex and increasingly flexible approaches for large-scale metabolic engineering in plant biotechnology.
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Production and characterization of tearless and non-pungent onion

Production and characterization of tearless and non-pungent onion | plant cell genetics | Scoop.it

The onion lachrymatory factor (LF) is produced from trans-S-1-propenyl-L-cysteine sulfoxide (PRENCSO) through successive reactions catalyzed by alliinase (EC 4.4.1.4) and lachrymatory factor synthase (LFS), and is responsible for the tear inducing-property and the pungency of fresh onions. We developed tearless, non-pungent onions non-transgenically by irradiating seeds with neon-ion at 20 Gy. The bulbs obtained from the irradiated seeds and their offspring bulbs produced by selfing were screened by organoleptic assessment of tear-inducing property or HPLC analysis of LF production. After repeated screening and seed production by selfing, two tearless, non-pungent bulbs were identified in the third generation (M3) bulbs. Twenty M4 bulbs obtained from each of them showed no tear-inducing property or pungency when evaluated by 20 sensory panelists. The LF production levels in these bulbs were approximately 7.5-fold lower than those of the normal onion. The low LF production levels were due to reduction in alliinase activity, which was a result of low alliinase mRNA expression (less than 1% of that in the normal onion) and consequent low amounts of the alliinase protein. These tearless, non-pungent onions should be welcomed by all who tear while chopping onions and those who work in facilities where fresh onions are processed.

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Convergence in the temperature response of leaf respiration across biomes and plant functional types

Convergence in the temperature response of leaf respiration across biomes and plant functional types | plant cell genetics | Scoop.it
A major concern for terrestrial biosphere models is accounting for the temperature response of leaf respiration at regional/global scales. Most biosphere models incorrectly assume that respiration increases exponentially with rising temperature, with profound effects for predicted ecosystem carbon exchange. Based on a study of 231 species in 7 biomes, we find that the rise in respiration with temperature can be generalized across biomes and plant types, with temperature sensitivity declining as leaves warm. This finding indicates universally conserved controls on the temperature sensitivity of leaf metabolism. Accounting for the temperature function markedly lowers simulated respiration rates in cold biomes, which has important consequences for estimates of carbon storage in vegetation, predicted concentrations of atmospheric carbon dioxide, and future surface temperatures.
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Higher temperature and increases CO2 fixation are not incompatible
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Cell-to-cell movement of mitochondria in plants

Cell-to-cell movement of mitochondria in plants | plant cell genetics | Scoop.it
We report cell-to-cell movement of mitochondria through a graft junction. Mitochondrial movement was discovered in an experiment designed to select for chloroplast transfer from Nicotiana sylvestris into Nicotiana tabacum cells. The alloplasmic N. tabacum line we used carries Nicotiana undulata cytoplasmic genomes, and its flowers are male sterile due to the foreign mitochondrial genome. Thus, rare mitochondrial DNA transfer from N. sylvestris to N. tabacum could be recognized by restoration of fertile flower anatomy. Analyses of the mitochondrial genomes revealed extensive recombination, tentatively linking male sterility to orf293, a mitochondrial gene causing homeotic conversion of anthers into petals. Demonstrating cell-to-cell movement of mitochondria reconstructs the evolutionary process of horizontal mitochondrial DNA transfer and enables modification of the mitochondrial genome by DNA transmitted from a sexually incompatible species. Conversion of anthers into petals is a visual marker that can be useful for mitochondrial transformation.
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Elucidation of the first committed step in betalain biosynthesis enables the heterologous engineering of betalain pigments in plants - Polturak - 2015 - New Phytologist - Wiley Online Library

Elucidation of the first committed step in betalain biosynthesis enables the heterologous engineering of betalain pigments in plants - Polturak - 2015 - New Phytologist - Wiley Online Library | plant cell genetics | Scoop.it
Betalains are tyrosine-derived red-violet and yellow pigments, found in plants only of the Caryophyllales order. Although much progress has been made in recent years in the understanding of the betalain biosynthetic process, many questions remain open with regards to several of the proposed steps in the pathway. Most conspicuous by its absence is the characterization of the first committed step in the pathway, namely the 3-hydroxylation of tyrosine to form l-3,4-dihydroxyphenylalanine (l-DOPA).
We used transcriptome analysis of the betalain-producing plants red beet (Beta vulgaris) and four o'clocks (Mirabilis jalapa) to identify a novel, betalain-related cytochrome P450-type gene, CYP76AD6, and carried out gene silencing and recombinant expression assays in Nicotiana benthamiana and yeast cells to examine its functionality.
l-DOPA formation in red beet was found to be redundantly catalyzed by CYP76AD6 together with a known betalain-related enzyme, CYP76AD1, which was previously thought to only catalyze a succeeding step in the pathway. While CYP76AD1 catalyzes both l-DOPA formation and its subsequent conversion to cyclo-DOPA, CYP76AD6 uniquely exhibits only tyrosine hydroxylase activity.
The new findings enabled us to metabolically engineer entirely red-pigmented tobacco plants through heterologous expression of three genes taking part in the fully decoded betalain biosynthetic pathway.
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Rescooped by Jean-Pierre Zryd from GMOs & Sustainable agriculture
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The enhancement of tolerance to salt and cold stresses by modifying the redox state and salicylic acid content via the cytosolic malate dehydrogenase gene in transgenic apple plants -

The enhancement of tolerance to salt and cold stresses by modifying the redox state and salicylic acid content via the cytosolic malate dehydrogenase gene in transgenic apple plants - | plant cell genetics | Scoop.it
In this paper, we characterized the role of an apple cytosolic malate dehydrogenase gene (MdcyMDH) in the tolerance to salt and cold stresses and investigated its regulation mechanism in stress tolerance. The MdcyMDH transcript was induced by mild cold and salt treatments, and MdcyMDH-overexpressing apple plants possessed improved cold and salt tolerance compared to wild type (WT) plants. A digital gene expression tag profiling analysis revealed that MdcyMDH overexpression largely altered some biological processes, including hormone signal transduction, photosynthesis, citrate cycle, and oxidation-reduction. Further experiments verified that MdcyMDH overexpression modified the mitochondrial and chloroplast metabolisms and elevated the level of reducing power, primarily caused by increased ascorbate and glutathione, as well as the increased ratios of ascorbate/dehydroascorbate and glutathione/glutathione disulfide, under normal and especially stress conditions. Concurrently, the transgenic plants produced a high H2O2 content, but a low O2·- production rate was observed compared to the WT plants. On the other hand, the transgenic plants accumulated more free and total salicylic acid (SA) than the WT plants under normal and stress conditions. Taken together, MdcyMDH conferred the transgenic apple plants a higher stress tolerance by producing more reductive redox states and increasing the SA level; MdcyMDH could serve as a target gene to genetically engineer salt- and cold-tolerant trees.

Via Christophe Jacquet
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