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Rescooped by Jennifer Mach from Plant Biology Teaching Resources (Higher Education)
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Teaching Tools in Plant Biology. Medicinal Plants: Past, Present and Future

Teaching Tools in Plant Biology. Medicinal Plants: Past, Present and Future | Emerging Research in Plant Cell Biology | Scoop.it

Plants produce thousands of specialized metabolites, many of which have medicinal uses. More than half of the top 150 prescribed drugs in the US have at least one compound derived from plants, and about 80% of the world's population depends on plants or plant extracts as a major source of healthcare. This lecture looks at the history of medicinal plants, herbal remedies in traditional and contemporary medicine, and ongoing efforts to identify novel medicinal compounds from plants. New approaches, such as metabolomics, metabolic engineering and systems and synthetic biology, are contributing towards the identification, characterization and production of plant-derived medicines.


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Emerging Research in Plant Cell Biology
A science editor's take on what's new and interesting in the plant kingdom.
Curated by Jennifer Mach
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Transcriptomic and physiological characterization of the fefe mutant of melon (Cucumis melo) reveals new aspects of iron–copper crosstalk

Transcriptomic and physiological characterization of the fefe mutant of melon (Cucumis melo) reveals new aspects of iron–copper crosstalk | Emerging Research in Plant Cell Biology | Scoop.it
Iron (Fe) and copper (Cu) homeostasis are tightly linked across biology. In previous work, Fe deficiency interacted with Cu-regulated genes and stimulated Cu accumulation.The C940-fe (fefe) Fe-uptake mutant of melon (Cucumis melo) was characterized, and the fefe mutant was used to test whether Cu deficiency could stimulate Fe uptake. Wild-type and fefe mutant transcriptomes were determined by RNA-seq under Fe and Cu deficiency.FeFe-regulated genes included core Fe uptake, metal homeostasis, and transcription factor genes. Numerous genes were regulated by both Fe and Cu. The fefe mutant was rescued by high Fe or by Cu deficiency, which stimulated ferric-chelate reductase activity,FRO2 expression, and Fe accumulation. Accumulation of Fe in Cu-deficient plants was independent of the normal Fe-uptake system. One of the four FRO genes in the melon and cucumber (Cucumis sativus) genomes was Fe-regulated, and one was Cu-regulated. Simultaneous Fe and Cu deficiency synergistically up-regulated Fe-uptake gene expression.Overlap in Fe and Cu deficiency transcriptomes highlights the importance of Fe–Cu crosstalk in metal homeostasis. The fefe gene is not orthologous to FIT, and thus identification of this gene will provide clues to help understand regulation of Fe uptake in plants.
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Plant, Cell & Environment - Volume 37, Issue 8 - Plant Volatiles

Plant, Cell & Environment - Volume 37, Issue 8 - Plant Volatiles | Emerging Research in Plant Cell Biology | Scoop.it

Special Issue on plant volatiles!

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Auxin transport sites are visualized in planta using fluorescent auxin analogs

The plant hormone auxin is a key morphogenetic signal that controls many aspects of plant growth and development. Cellular auxin levels are coordinately regulated by multiple processes, including auxin biosynthesis and the polar transport and metabolic pathways. The auxin concentration gradient determines plant organ positioning and growth responses to environmental cues. Auxin transport systems play crucial roles in the spatiotemporal regulation of the auxin gradient. This auxin gradient has been analyzed using SCF-type E3 ubiquitin-ligase complex-based auxin biosensors in synthetic auxin-responsive reporter lines. However, the contributions of auxin biosynthesis and metabolism to the auxin gradient have been largely elusive. Additionally, the available information on subcellular auxin localization is still limited. Here we designed fluorescently labeled auxin analogs that remain active for auxin transport but are inactive for auxin signaling and metabolism. Fluorescent auxin analogs enable the selective visualization of the distribution of auxin by the auxin transport system. Together with auxin biosynthesis inhibitors and an auxin biosensor, these analogs indicated a substantial contribution of local auxin biosynthesis to the formation of auxin maxima at the root apex. Moreover, fluorescent auxin analogs mainly localized to the endoplasmic reticulum in cultured cells and roots, implying the presence of a subcellular auxin gradient in the cells. Our work not only provides a useful tool for the plant chemical biology field but also demonstrates a new strategy for imaging the distribution of small-molecule hormones.

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The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria

The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria | Emerging Research in Plant Cell Biology | Scoop.it

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3–C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect.

Jennifer Mach's insight:

Also Insight from eLife:

http://elifesciences.org/content/3/e03702

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TAA1-Regulated Local Auxin Biosynthesis in the Root-Apex Transition Zone Mediates the Aluminum-Induced Inhibition of Root Growth in Arabidopsis

TAA1-Regulated Local Auxin Biosynthesis in the Root-Apex Transition Zone Mediates the Aluminum-Induced Inhibition of Root Growth in Arabidopsis | Emerging Research in Plant Cell Biology | Scoop.it

The transition zone (TZ) of the root apex is the perception site of Al toxicity. Here, we show that exposure of Arabidopsis thaliana roots to Al induces a localized enhancement of auxin signaling in the root-apex TZ that is dependent on TAA1, which encodes a Trp aminotransferase and regulates auxin biosynthesis. TAA1 is specifically upregulated in the root-apex TZ in response to Al treatment, thus mediating local auxin biosynthesis and inhibition of root growth. The TAA1-regulated local auxin biosynthesis in the root-apex TZ in response to Al stress is dependent on ethylene, as revealed by manipulating ethylene homeostasis via the precursor of ethylene biosynthesis 1-aminocyclopropane-1-carboxylic acid, the inhibitor of ethylene biosynthesis aminoethoxyvinylglycine, or mutant analysis. In response to Al stress, ethylene signaling locally upregulates TAA1 expression and thus auxin responses in the TZ and results in auxin-regulated root growth inhibition through a number of auxin response factors (ARFs). In particular, ARF10 and ARF16 are important in the regulation of cell wall modification–related genes. Our study suggests a mechanism underlying how environmental cues affect root growth plasticity through influencing local auxin biosynthesis and signaling.

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Plant biology informs drug discovery

In times of tight budgets, researchers are frequently asked to focus on 'translational science', although paradigm-shifting breakthroughs often emerge from basic research that is conducted without aiming for therapeutically relevant applications. An unconventional marriage between plant biology and embryology provides a striking example.

Auxins are a class of phytohormones that regulate…

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A link between auxin functions and the birth defects caused by thalidomide? 

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Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew

Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew | Emerging Research in Plant Cell Biology | Scoop.it

Sequence-specific nucleases have been applied to engineer targeted modifications in polyploid genomes1, but simultaneous modification of multiple homoeoalleles has not been reported. Here we use transcription activator–like effector nuclease (TALEN)2, 3 and clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 (refs. 4,5) technologies in hexaploid bread wheat to introduce targeted mutations in the three homoeoalleles that encode MILDEW-RESISTANCE LOCUS (MLO) proteins6. Genetic redundancy has prevented evaluation of whether mutation of all three MLO alleles in bread wheat might confer resistance to powdery mildew, a trait not found in natural populations7. We show that TALEN-induced mutation of all three TaMLOhomoeologs in the same plant confers heritable broad-spectrum resistance to powdery mildew. We further use CRISPR-Cas9 technology to generate transgenic wheat plants that carry mutations in the TaMLO-A1 allele. We also demonstrate the feasibility of engineering targeted DNA insertion in bread wheat through nonhomologous end joining of the double-strand breaks caused by TALENs. Our findings provide a methodological framework to improve polyploid crops.

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Rescooped by Jennifer Mach from Plant roots and rhizosphere
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Control of phosphate homeostasis through gene regulation in crops

Control of phosphate homeostasis through gene regulation in crops | Emerging Research in Plant Cell Biology | Scoop.it

Phosphorus (P) is an essential yet frequently deficient element in plants. Maintenance of phosphate (Pi) homeostasis is crucial for crop production. In comparison with the model plant Arabidopsis, crops face wider ranges and larger fluctuations in P supply from the soil environment, and thus develop more complicated strategies to improve Pi acquisition and utilization efficiency. Undergirding these strategies, there are numerous genes involved in alternative metabolism pathways that are regulated by complex Pi signaling networks. In this review, we intend to summarize the recent advances in crops on control of Pi homeostasis through gene regulation from Pi acquisition and mobilization within plants, as well as activation of rhizosphere P and P uptake through symbiotic associations.


Via Christophe Jacquet
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A global database of C4 photosynthesis in grasses

A global database of C4 photosynthesis in grasses | Emerging Research in Plant Cell Biology | Scoop.it

C3, C4 or Crassulacean acid metabolism (CAM) photosynthetic
pathways represent a fundamental axis of trait variation in plants,
with importance at scales from genome to biome. Knowing the
distribution of these pathways among wild species is a crucial first
step in understanding the patterns and processes of photosynthetic
evolution and its role in ecological processes at large scales.


Via Pierre-Marc Delaux
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Closing the carbon cycle: Current Biology

Closing the carbon cycle: Current Biology | Emerging Research in Plant Cell Biology | Scoop.it

The Sun sends us much more energy than we need, but we have yet to learn how to capture, store, and distribute it efficiently. And while we’re learning, we continue to deplete solar energy that nature stored for us many millions of years ago in the shape of fossil fuels and to increase the carbon dioxide content of the atmosphere.

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Comparative Phylogenomics Uncovers the Impact of Symbiotic Associations on Host Genome Evolution

Comparative Phylogenomics Uncovers the Impact of Symbiotic Associations on Host Genome Evolution | Emerging Research in Plant Cell Biology | Scoop.it

Mutualistic symbioses between eukaryotes and beneficial microorganisms of their microbiome play an essential role in nutrition, protection against disease, and development of the host. However, the impact of beneficial symbionts on the evolution of host genomes remains poorly characterized. Here we used the independent loss of the most widespread plant–microbe symbiosis, arbuscular mycorrhization (AM), as a model to address this question. Using a large phenotypic approach and phylogenetic analyses, we present evidence that loss of AM symbiosis correlates with the loss of many symbiotic genes in the Arabidopsis lineage (Brassicales). Then, by analyzing the genome and/or transcriptomes of nine other phylogenetically divergent non-host plants, we show that this correlation occurred in a convergent manner in four additional plant lineages, demonstrating the existence of an evolutionary pattern specific to symbiotic genes. Finally, we use a global comparative phylogenomic approach to track this evolutionary pattern among land plants. Based on this approach, we identify a set of 174 highly conserved genes and demonstrate enrichment in symbiosis-related genes. Our findings are consistent with the hypothesis that beneficial symbionts maintain purifying selection on host gene networks during the evolution of entire lineages.

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Multiple FLC haplotypes defined by independent cis-regulatory variation underpin life history diversity in Arabidopsis thaliana

Multiple FLC haplotypes defined by independent cis-regulatory variation underpin life history diversity in Arabidopsis thaliana | Emerging Research in Plant Cell Biology | Scoop.it

Relating molecular variation to phenotypic diversity is a central goal in evolutionary biology. In Arabidopsis thaliana, FLOWERING LOCUS C (FLC) is a major determinant of variation in vernalization—the acceleration of flowering by prolonged cold. Here, through analysis of 1307 A. thaliana accessions, we identify five predominant FLC haplotypes defined by noncoding sequence variation. Genetic and transgenic experiments show that they are functionally distinct, varying in FLC expression level and rate of epigenetic silencing. Allelic heterogeneity at this single locus accounts for a large proportion of natural variation in vernalization that contributes to adaptation of A. thaliana.

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Paired-End Analysis of Transcription Start Sites in Arabidopsis Reveals Plant-Specific Promoter Signatures

Paired-End Analysis of Transcription Start Sites in Arabidopsis Reveals Plant-Specific Promoter Signatures | Emerging Research in Plant Cell Biology | Scoop.it

Understanding plant gene promoter architecture has long been a challenge due to the lack of relevant large-scale data sets and analysis methods. Here, we present a publicly available, large-scale transcription start site (TSS) data set in plants using a high-resolution method for analysis of 5′ ends of mRNA transcripts. Our data set is produced using the paired-end analysis of transcription start sites (PEAT) protocol, providing millions of TSS locations from wild-type Columbia-0Arabidopsis thaliana whole root samples. Using this data set, we grouped TSSreads into “TSS tag clusters” and categorized clusters into three spatial initiation patterns: narrow peak, broad with peak, and weak peak. We then designed a machine learning model that predicts the presence of TSS tag clusters with outstanding sensitivity and specificity for all three initiation patterns. We used this model to analyze the transcription factor binding site content of promoters exhibiting these initiation patterns. In contrast to the canonical notions of TATA-containing and more broad “TATA-less” promoters, the model shows that, in plants, the vast majority of transcription start sites are TATA free and are defined by a large compendium of known DNA sequence binding elements. We present results on the usage of these elements and provide our Plant PEAT Peaks (3PEAT) model that predicts the presence of TSSs directly from sequence.

Jennifer Mach's insight:

Plus In Brief mini-review:

http://www.plantcell.org/content/early/2014/07/17/tpc.114.129239.full.pdf+html

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Variation in allelic expression associated with a recombination hotspot in Zea mays

Variation in allelic expression associated with a recombination hotspot in Zea mays | Emerging Research in Plant Cell Biology | Scoop.it

Gene expression is a complex process, requiring precise spatial and temporal regulation of transcription factor activity; however, modifications of individual cis- and trans-acting modules can be molded by natural selection to create a sizeable number of novel phenotypes. Results from decades of research indicate that developmental and phenotypic divergence among eukaryotic organisms is driven primarily by variation in levels of gene expression that are dictated by mutations, either in structural or regulatory regions, of genes. The relative contributions and interplay of cis- and trans-acting regulatory factors to this evolutionary process, however, remain poorly understood. Analysis of eight genes in the Bz1–Sh1 interval of Zea mays (maize) indicates significant allele-specific expression biases in at least one tissue for all genes, ranging from 1.3-fold to 36-fold. All detected effects were cis-regulatory in nature, although genetic background may also influence the level of expression bias and tissue specificity for some allelic combinations. Most allelic pairs exhibited the same direction and approximate intensity of bias across all four tissues; however, a subset of allelic pairs show alternating dominance across different tissue types or variation in the degree of bias in different tissues. In addition, the genes showing the most striking levels of allelic bias co-localize with a previously described recombination hotspot in this region, suggesting a naturally occurring genetic mechanism for creating regulatory variability for a subset of plant genes that may ultimately lead to evolutionary diversification.

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Dt2 Is a Gain-of-Function MADS-Domain Factor Gene That Specifies Semideterminacy in Soybean

Dt2 Is a Gain-of-Function MADS-Domain Factor Gene That Specifies Semideterminacy in Soybean | Emerging Research in Plant Cell Biology | Scoop.it

Similar to Arabidopsis thaliana, the wild soybeans (Glycine soja) and many cultivars exhibit indeterminate stem growth specified by the shoot identity gene Dt1, the functional counterpart of Arabidopsis TERMINAL FLOWER1 (TFL1). Mutations inTFL1 and Dt1 both result in the shoot apical meristem (SAM) switching from vegetative to reproductive state to initiate terminal flowering and thus produce determinate stems. A second soybean gene (Dt2) regulating stem growth was identified, which, in the presence of Dt1, produces semideterminate plants with terminal racemes similar to those observed in determinate plants. Here, we report positional cloning and characterization of Dt2, a dominant MADS domain factor gene classified into the APETALA1/SQUAMOSA (AP1/SQUA) subfamily that includes floral meristem (FM) identity genes AP1, FUL, and CAL in Arabidopsis. Unlike AP1, whose expression is limited to FMs in which the expression of TFL1 is repressed,Dt2 appears to repress the expression of Dt1 in the SAMs to promote early conversion of the SAMs into reproductive inflorescences. Given that Dt2 is not the gene most closely related to AP1 and that semideterminacy is rarely seen in wild soybeans, Dt2 appears to be a recent gain-of-function mutation, which has modified the genetic pathways determining the stem growth habit in soybean.

Jennifer Mach's insight:

Bonus content: In Brief 

http://www.plantcell.org/content/early/2014/07/08/tpc.114.129056.full.pdf+html

and profile of lead author: 

http://www.plantcell.org/content/early/2014/07/08/tpc.114.126938/suppl/DC2

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Host-induced bacterial cell wall decomposition mediates pattern-triggered immunity in Arabidopsis

Host-induced bacterial cell wall decomposition mediates pattern-triggered immunity in Arabidopsis | Emerging Research in Plant Cell Biology | Scoop.it

Peptidoglycans (PGNs) are immunogenic bacterial surface patterns that trigger immune activation in metazoans and plants. It is generally unknown how complex bacterial structures such as PGNs are perceived by plant pattern recognition receptors (PRRs) and whether host hydrolytic activities facilitate decomposition of bacterial matrices and generation of soluble PRR ligands. Here we show that Arabidopsis thaliana, upon bacterial infection or exposure to microbial patterns, produces a metazoan lysozyme-like hydrolase (lysozyme 1, LYS1). LYS1 activity releases soluble PGN fragments from insoluble bacterial cell walls and cleavage products are able to trigger responses typically associated with plant immunity. Importantly, LYS1 mutant genotypes exhibit super-susceptibility to bacterial infections similar to that observed on PGN receptor mutants. We propose that plants employ hydrolytic activities for the decomposition of complex bacterial structures, and that soluble pattern generation might aid PRR-mediated immune activation in cell layers adjacent to infection sites.

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Nature: The long-term maintenance of a resistance polymorphism through diffuse interactions (2014)

Nature: The long-term maintenance of a resistance polymorphism through diffuse interactions (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Plant resistance (R) genes are a crucial component in plant defence against pathogens1. Although R genes often fail to provide durable resistance in an agricultural context, they frequently persist as long-lived balanced polymorphisms in nature2, 3, 4. Standard theory explains the maintenance of such polymorphisms through a balance of the costs and benefits of resistance and virulence in a tightly coevolving host–pathogen pair5, 6. However, many plant–pathogen interactions lack such specificity7. Whether, and how, balanced polymorphisms are maintained in diffusely interacting species8 is unknown. Here we identify a naturally interacting R gene and effector pair in Arabidopsis thaliana and its facultative plant pathogen, Pseudomonas syringae. The protein encoded by the R gene RPS5 recognizes an AvrPphB homologue (AvrPphB2) and exhibits a balanced polymorphism that has been maintained for over 2 million years (ref. 3). Consistent with the presence of an ancient balanced polymorphism, the R gene confers a benefit when plants are infected with P. syringae carrying avrPphB2 but also incurs a large cost in the absence of infection. RPS5alleles are maintained at intermediate frequencies in populations globally, suggesting ubiquitous selection for resistance. However, the presence of P. syringae carrying avrPphB is probably insufficient to explain the RPS5 polymorphism. First, avrPphB homologues occur at very low frequencies in P. syringae populations on A. thaliana. Second, AvrPphB only rarely confers a virulence benefit to P. syringae on A. thaliana. Instead, we find evidence that selection for RPS5 involves multiple non-homologous effectors and multiple pathogen species. These results and an associated model suggest that the R gene polymorphism in A. thaliana may not be maintained through a tightly coupled interaction involving a single coevolved R gene and effector pair. More likely, the stable polymorphism is maintained through complex and diffuse community-wide interactions.


Via Kamoun Lab @ TSL
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Epigenetic reprogramming in plant sexual reproduction

Epigenetic reprogramming in plant sexual reproduction | Emerging Research in Plant Cell Biology | Scoop.it

Epigenetic reprogramming consists of global changes in DNA methylation and histone modifications. In mammals, epigenetic reprogramming is primarily associated with sexual reproduction and occurs during both gametogenesis and early embryonic development. Such reprogramming is crucial not only to maintain genomic integrity through silencing transposable elements but also to reset the silenced status of imprinted genes. In plants, observations of stable transgenerational inheritance of epialleles have argued against reprogramming. However, emerging evidence supports that epigenetic reprogramming indeed occurs during sexual reproduction in plants and that it has a major role in maintaining genome integrity and a potential contribution to epiallelic variation.

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Molecular genetic framework for protophloem formation

The phloem performs essential systemic functions in tracheophytes, yet little is known about its molecular genetic specification. Here we show that application of the peptide ligand CLAVATA3/EMBRYO SURROUNDING REGION 45 (CLE45) specifically inhibits specification of protophloem in Arabidopsis roots by locking the sieve element precursor cell in its preceding developmental state. CLE45 treatment, as well as viable transgenic expression of a weak CLE45G6T variant, interferes not only with commitment to sieve element fate but also with the formative sieve element precursor cell division that creates protophloem and metaphloem cell files. However, the absence of this division appears to be a secondary effect of discontinuous sieve element files and subsequent systemically reduced auxin signaling in the root meristem. In the absence of the formative sieve element precursor cell division, metaphloem identity is seemingly adopted by the normally procambial cell file instead, pointing to possibly independent positional cues for metaphloem formation. The protophloem formation and differentiation defects in brevis radix (brx) andoctopus (ops) mutants are similar to those observed in transgenic seedlings with increased CLE45 activity and can be rescued by loss of function of a putative CLE45 receptor, BARELY ANY MERISTEM 3 (BAM3). Conversely, a dominant gain-of-function ops allele or mild OPS dosage increase suppresses brx defects and confers CLE45 resistance. Thus, our data suggest that delicate quantitative interplay between the opposing activities of BAM3-mediated CLE45 signals and OPS-dependent signals determines cellular commitment to protophloem sieve element fate, with OPS acting as a positive, quantitative master regulator of phloem fate.

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Mating system shifts and transposable element evolution in the plant genus Capsella

Mating system shifts and transposable element evolution in the plant genus Capsella | Emerging Research in Plant Cell Biology | Scoop.it
Despite having predominately deleterious fitness effects, transposable elements (TEs) are major constituents of eukaryote genomes in general and of plant genomes in particular. Although the proportion of the genome made up of TEs varies at least four-fold across plants, the relative importance of the evolutionary forces shaping variation in TE abundance and distributions across taxa remains unclear. Under several theoretical models, mating system plays an important role in governing the evolutionary dynamics of TEs. Here, we use the recently sequenced Capsella rubella reference genome and short-read whole genome sequencing of multiple individuals to quantify abundance, genome distributions, and population frequencies of TEs in three recently diverged species of differing mating system, two self-compatible species (C. rubella and C. orientalis) and their self-incompatible outcrossing relative, C. grandiflora.
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Exploring the functional soil-microbe interface and exoenzymes through soil metaexoproteomics

Exploring the functional soil-microbe interface and exoenzymes through soil metaexoproteomics | Emerging Research in Plant Cell Biology | Scoop.it

Functionally important proteins at the interface of cell and soil are of potentially low abundance when compared with commonly recovered intracellular proteins. A novel approach was developed and used to extract the metaexoproteome, the subset of proteins found outside the cell, in the context of a soil enriched with the nitrogen-containing recalcitrant polymer chitin. The majority of proteins recovered was of bacterial origin and localized to the outer membrane or extracellular milieu. A wide variety of transporter proteins were identified, particularly those associated with amino-acid and phosphate uptake. The metaexoproteome extract retained chitinolytic activity and we were successful in detecting Nocardiopsis-like chitinases that correlated with the glycoside hydrolase family 18 (GH18)chi gene data and metataxonomic analysis. Nocardiopsis-like chitinases appeared to be solely responsible for chitinolytic activity in soil. This is the first study to detect and sequence bacterial exoenzymes with proven activity in the soil enzyme pool.


Via Jean-Michel Ané, Francis Martin, Christophe Jacquet
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Jean-Michel Ané's curator insight, July 18, 12:28 PM

After metaproteomics, here is metaexoproteomics!

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The impact of widespread regulatory neofunctionalization on homeolog gene evolution following whole-genome duplication in maize

Whole-genome duplications are a widespread feature of plant genome evolution, having been detected in all flowering plant lineages. Despite the prevalence of these events, the extent to which duplicated genes (homeolog gene pairs) functionally diverge (neofunctionalization) is unclear. We present a genome-wide analysis of molecular evolution and regulatory neofunctionalization in maize (Zea mays L.). We demonstrate that 13% of all homeolog gene pairs in maize are regulatory neofunctionalized in leaves, and that regulatory neofunctionalized genes experience enhanced purifying selection. We show that significantly more genes have been regulatory neofunctionalized in foliar leaves than in husk leaves and that both leaf types have experienced selection for distinct functional roles. Furthermore, we demonstrate that biased subgenome expression dominance occurs only in the presence of regulatory neofunctionalization and that in nonregulatory neofunctionalized genes subgenome dominance is progressively acquired during development. Taken together, our study reveals several novel insights into the evolution of maize, genes, and gene expression, and provides a general model for gene evolution following whole-genome duplication in plants.An international, peer-reviewed genome sciences journal featuring outstanding original research that offers novel insights into the biology of all organisms

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Polyploid Evolution of the Brassicaceae during the Cenozoic Era

Polyploid Evolution of the Brassicaceae during the Cenozoic Era | Emerging Research in Plant Cell Biology | Scoop.it

The Brassicaceae (Cruciferae) family, owing to its remarkable species, genetic, and physiological diversity as well as its significant economic potential, has become a model for polyploidy and evolutionary studies. Utilizing extensive transcriptome pyrosequencing of diverse taxa, we established a resolved phylogeny of a subset of crucifer species. We elucidated the frequency, age, and phylogenetic position of polyploidy and lineage separation events that have marked the evolutionary history of the Brassicaceae. Besides the well-known ancient α (47 million years ago [Mya]) and β (124 Mya) paleopolyploidy events, several species were shown to have undergone a further more recent (∼7 to 12 Mya) round of genome multiplication. We identified eight whole-genome duplications corresponding to at least five independent neo/mesopolyploidy events. Although the Brassicaceae family evolved from other eudicots at the beginning of the Cenozoic era of the Earth (60 Mya), major diversification occurred only during the Neogene period (0 to 23 Mya). Remarkably, the widespread species divergence, major polyploidy, and lineage separation events during Brassicaceae evolution are clustered in time around epoch transitions characterized by prolonged unstable climatic conditions. The synchronized diversification of Brassicaceae species suggests that polyploid events may have conferred higher adaptability and increased tolerance toward the drastically changing global environment, thus facilitating species radiation.

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Arabidopsis thaliana WAPL Is Essential for the Prophase Removal of Cohesin during Meiosis

Arabidopsis thaliana WAPL Is Essential for the Prophase Removal of Cohesin during Meiosis | Emerging Research in Plant Cell Biology | Scoop.it

Sister chromatid cohesion, which is mediated by the cohesin complex, is essential for the proper segregation of chromosomes in mitosis and meiosis. The establishment of stable sister chromatid cohesion occurs during DNA replication and involves acetylation of the complex by the acetyltransferase CTF7. In higher eukaryotes, the majority of cohesin complexes are removed from chromosomes during prophase. Studies in fly and human have shown that this process involves the WAPL mediated opening of the cohesin ring at the junction between the SMC3 ATPase domain and the N-terminal domain of cohesin's α-kleisin subunit. We report here the isolation and detailed characterization of WAPL in Arabidopsis thaliana. We show that Arabidopsis contains two WAPL genes, which share overlapping functions. Plants in which both WAPL genes contain T-DNA insertions show relatively normal growth and development but exhibit a significant reduction in male and female fertility. The removal of cohesin from chromosomes during meiotic prophase is blocked in Atwapl mutants resulting in chromosome bridges, broken chromosomes and uneven chromosome segregation. In contrast, while subtle mitotic alterations are observed in some somatic cells, cohesin complexes appear to be removed normally. Finally, we show that mutations in AtWAPL suppress the lethality associated with inactivation of AtCTF7. Taken together our results demonstrate that WAPL plays a critical role in meiosis and raises the possibility that mechanisms involved in the prophase removal of cohesin may vary between mitosis and meiosis in plants.

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Regulating gene drives

Regulatory gaps must be filled before gene drives could be used in the wild.

Jennifer Mach's insight:

Also in eLife: http://elifesciences.org/content/early/2014/07/17/eLife.03401

 

...and an article by Carl Zimmer on applications in malaria:

http://www.nytimes.com/2014/07/17/science/a-call-to-fight-malaria-one-mosquito-at-a-time-by-altering-dna.html?_r=0

 

After so much thought about "gene flow control" for transgenic plants, it's interesting to think about the opposite problem-- mechanisms for spreading a genetic modification.

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