plant molecular biology
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Rescooped by Guojian HU from Emerging Research in Plant Cell Biology
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Chilling-induced tomato flavor loss is associated with altered volatile synthesis and transient changes in DNA methylation

Commercial tomatoes are widely perceived by consumers as lacking flavor. A major part of that problem is a postharvest handling system that chills fruit. Low-temperature storage is widely used to slow ripening and reduce decay. However, chilling results in loss of flavor. Flavor-associated volatiles are sensitive to temperatures below 12 °C, and their loss greatly reduces flavor quality. Here, we provide a comprehensive view of the effects of chilling on flavor and volatiles associated with consumer liking. Reduced levels of specific volatiles are associated with significant reductions in transcripts encoding key volatile synthesis enzymes. Although expression of some genes critical to volatile synthesis recovers after a return to 20 °C, some genes do not. RNAs encoding transcription factors essential for ripening, including RIPENING INHIBITOR (RIN), NONRIPENING, and COLORLESS NONRIPENING are reduced in response to chilling and may be responsible for reduced transcript levels in many downstream genes during chilling. Those reductions are accompanied by major changes in the methylation status of promoters, including RIN. Methylation changes are transient and may contribute to the fidelity of gene expression required to provide maximal beneficial environmental response with minimal tangential influence on broader fruit developmental biology.


Via Jennifer Mach
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Rescooped by Guojian HU from Plant development and evolution
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A flower is born: an update on Arabidopsis floral meristem formation

A flower is born: an update on Arabidopsis floral meristem formation | plant molecular biology | Scoop.it
"In Arabidopsis, floral meristems appear on the flanks of the inflorescence meristem. Their stereotypic development, ultimately producing the four whorls of floral organs, is essentially controlled by a network coordinating growth and cell-fate determination. This network integrates hormonal signals, transcriptional regulators, and mechanical constraints. Mechanisms regulating floral meristem formation have been studied at many different scales, from protein structure to tissue modeling. In this paper, we review recent findings related to the emergence of the floral meristem and floral fate determination and examine how this field has been impacted by recent technological developments."

Via CHAHTANE Hicham
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Arabidopsis transcriptional repressor VAL1 triggers Polycomb silencing at FLC during vernalization. - Science

Arabidopsis transcriptional repressor VAL1 triggers Polycomb silencing at FLC during vernalization. - Science | plant molecular biology | Scoop.it
Abstract
The determinants that specify the genomic targets of Polycomb silencing complexes are still unclear. Polycomb silencing of Arabidopsis FLOWERING LOCUS C (FLC) accelerates flowering and involves a cold-dependent epigenetic switch. Here we identify a single point mutation at an intragenic nucleation site within FLC that prevents this epigenetic switch from taking place. The mutation blocks nucleation of plant homeodomain-Polycomb repressive complex 2 (PHD-PRC2) and indicates a role for the transcriptional repressor VAL1 in the silencing mechanism. VAL1 localizes to the nucleation region in vivo, promoting histone deacetylation and FLC transcriptional silencing, and interacts with components of the conserved apoptosis- and splicing-associated protein (ASAP) complex. Sequence-specific targeting of transcriptional repressors thus recruits the machinery for PHD-PRC2 nucleation and epigenetic silencing.

Via Loïc Lepiniec
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Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins

Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins | plant molecular biology | Scoop.it
Constitutive auxin response in Physcomitrella reveals complex interactions between Aux/IAA and ARF proteins | The auxin-sensitive Aux/IAA transcriptional repressors regulate approximately 35% of the annotated genes in Physcomitrella patens and exhibit complex interactions with both the activating and repressing ARF transcription factors.

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Writing workshop 2016

How to write scientific research articles- from structuring your paper to polishing it, ethical issues in writing and figure preparation, and peer review

Via Mary Williams
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I ran a two-hour writing workshop for scientists yesterday at the University of Nottingham - here are my slides.

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Mary Williams's curator insight, March 10, 7:28 AM

I ran a two-hour writing workshop for scientists yesterday at the University of Nottingham - here are my slides.

Jennifer Mach's curator insight, March 21, 3:51 PM

I ran a two-hour writing workshop for scientists yesterday at the University of Nottingham - here are my slides.

Thirumurugan's curator insight, March 26, 5:05 AM

I ran a two-hour writing workshop for scientists yesterday at the University of Nottingham - here are my slides.

Rescooped by Guojian HU from Plant hormones and signaling peptides
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Embryonic lethality of Arabidopsis abp1-1 is caused by deletion of the adjacent BSM gene

Embryonic lethality of Arabidopsis abp1-1 is caused by deletion of the adjacent BSM gene | plant molecular biology | Scoop.it
Decades of research have suggested that AUXIN BINDING PROTEIN 1 (ABP1) is an essential membrane-associated auxin receptor, but recent findings directly contradict this view. Here we show that embryonic lethality observed in abp1-1, which has been a cornerstone of ABP1 studies, is caused by the deletion of the neighbouring BELAYA SMERT (BSM) gene, not by disruption of ABP1. On the basis of our results, we conclude that ABP1 is not essential for Arabidopsis development.

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Auxin-regulated chromatin switch directs acquisition of flower primordium founder fate | eLife

Auxin-regulated chromatin switch directs acquisition of flower primordium founder fate | eLife | plant molecular biology | Scoop.it

Reprogramming of cell identities during development frequently requires changes in the chromatin state that need to be restricted to the correct cell populations. Here we identify an auxin hormone-regulated chromatin state switch that directs reprogramming from transit amplifying to primordium founder cell fate in Arabidopsis inflorescences. Upon auxin sensing, the MONOPTEROS transcription factor recruits SWI/SNF chromatin remodeling ATPases to increase accessibility of the DNA for induction of key regulators of flower primordium initiation. In the absence of the hormonal cue, auxin sensitive Aux/IAA proteins bound to MONOPTEROS block recruitment of the SWI/SNF chromatin remodeling ATPases in addition to recruiting a co-repressor/histone deacetylase complex. This simple and elegant hormone-mediated chromatin state switch is ideally suited for iterative flower primordium initiation and orchestrates additional auxin-regulated cell fate transitions. Our findings establish a new paradigm for nuclear response to auxin. They also provide an explanation for how this small molecule can direct diverse plant responses.SWI/SNF chromatin remodeling complexes act as ‘gatekeepers’ for auxin responses and directly interact with the auxin response factor MONOPTEROS.


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A Scalable Genome-Editing-Based Approach for Mapping Multiprotein Complexes in Human Cells - Cell Reports

A Scalable Genome-Editing-Based Approach for Mapping Multiprotein Complexes in Human Cells - Cell Reports | plant molecular biology | Scoop.it

(via T. Lahaye, thx)

Dalvai et al, 2015

Conventional affinity purification followed by mass spectrometry (AP-MS) analysis is a broadly applicable method used to decipher molecular interaction networks and infer protein function. However, it is sensitive to perturbations induced by ectopically overexpressed target proteins and does not reflect multilevel physiological regulation in response to diverse stimuli. Here, we developed an interface between genome editing and proteomics to isolate native protein complexes produced from their natural genomic contexts. We used CRISPR/Cas9 and TAL effector nucleases (TALENs) to tag endogenous genes and purified several DNA repair and chromatin-modifying holoenzymes to near homogeneity. We uncovered subunits and interactions among well-characterized complexes and report the isolation of MCM8/9, highlighting the efficiency and robustness of the approach. These methods improve and simplify both small- and large-scale explorations of protein interactions as well as the study of biochemical activities and structure-function relationships.


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Rescooped by Guojian HU from Emerging Research in Plant Cell Biology
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A DEMETER-like DNA demethylase governs tomato fruit ripening

A DEMETER-like DNA demethylase governs tomato fruit ripening | plant molecular biology | Scoop.it

In plants, genomic DNA methylation which contributes to development and stress responses can be actively removed by DEMETER-like DNA demethylases (DMLs). Indeed, in Arabidopsis DMLs are important for maternal imprinting and endosperm demethylation, but only a few studies demonstrate the developmental roles of active DNA demethylation conclusively in this plant. Here, we show a direct cause and effect relationship between active DNA demethylation mainly mediated by the tomato DML, SlDML2, and fruit ripening— an important developmental process unique to plants. RNAi SlDML2 knockdown results in ripening inhibition via hypermethylation and repression of the expression of genes encoding ripening transcription factors and rate-limiting enzymes of key biochemical processes such as carotenoid synthesis. Our data demonstrate that active DNA demethylation is central to the control of ripening in tomato.


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Rescooped by Guojian HU from Plant & Evolution
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Model for perianth formation in orchids

Orchidaceae, the orchid family under the order Asparagales, contains more than 20,000 accepted species in approximately 880 genera1,2,3. In contrast to most flowers of actinomorphic symmetry, orchid flowers typically have zygomorphic symmetry with a striking well-differentiated labellum (lip) that acts as the main pollinator attractant by employing visual, fragrance and tactile cues4,5,6,7. Genetics models controlling patterning formation of actinomorphic flowers, such as Arabidopsis, are well known. However, the mechanisms of sepal/petal/lip determination remain obscure. Here, we demonstrate a conserved principle, called the Perianth (P) code, which involves competition between two protein complexes containing different AP3/AGL6 homologues to determine the formation of the complex perianth patterns in orchids. In the P code, the higher-order heterotetrameric SP (sepal/petal) complex (OAP3-1/OAGL6-1/OAGL6-1/OPI) specifies sepal/petal formation, whereas the L (lip) complex (OAP3-2/OAGL6-2/OAGL6-2/OPI) is exclusively required for lip formation. This model is validated by the conversion of lips into sepal/petal structures inOncidium and Phalaenopsis orchids through the suppression of the proposed L complex activity in lips using the virus-induced gene silencing (VIGS) strategy. A comprehensive examination of four different subfamilies of Orchidaceae further validates the P code and significantly extends the current knowledge regarding the mechanism and pathways of perianth formation in orchids.


Via Pierre-Marc Delaux
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Rescooped by Guojian HU from Emerging Research in Plant Cell Biology
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Endogenous Arabidopsis messenger RNAs transported to distant tissues

Endogenous Arabidopsis messenger RNAs transported to distant tissues | plant molecular biology | Scoop.it

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


Via Jennifer Mach
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attractive!

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Rescooped by Guojian HU from Emerging Research in Plant Cell Biology
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The Arabidopsis DNA Polymerase δ Has a Role in the Deposition of Transcriptionally Active Epigenetic Marks, Development and Flowering

The  Arabidopsis  DNA Polymerase δ Has a Role in the Deposition of Transcriptionally Active Epigenetic Marks, Development and Flowering | plant molecular biology | Scoop.it
Author Summary Three DNA polymerases replicate DNA in Eukaryotes. DNA polymerase α (Polα) initiates strand synthesis, which is performed by Polε and Polδ in leading and lagging strands, respectively. Not only the information encoded in the DNA, but also the inheritance of chromatin states is essential during development. Loss of function mutants in DNA polymerases lead to lethal phenotypes. Hence, hypomorphic alleles are necessary to study their roles beyond DNA replication. Here we identify a thermosensitive mutant of the Polδ in the model plant Arabidopsis thaliana , which bears an aminoacid substitution in the polymerase-domain. The mutants were essentially normal at 18°C but arrested development at 28°C. Interestingly, at 24°C we were able to study the roles of Polδ in epigenetic inheritance and plant development. We observed a tight connection between DNA replication stress and an increase the deposition of transcriptionally active chromatin marks in the SEPALLATA3 ( SEP3 ) locus. Finally, we tested by genetic means that the ectopic expression of SEP3 was indeed the cause of early flowering and the leaf phenotypes by promoting the expression of FLOWERING LOCUS T ( FT ). These results link Polδ activity to the proper establishment of transcriptionally active epigenetic marks, which then impact the development of multicellular organisms.

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Statistics for biologists – A free Nature Collection

Statistics for biologists – A free Nature Collection | plant molecular biology | Scoop.it

Great collection of free articles and guides from Nature


Via Mary Williams, Jennifer Mach
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Widespread natural variation of DNA methylation within angiosperms

Widespread natural variation of DNA methylation within angiosperms | plant molecular biology | Scoop.it
DNA methylation is an important feature of plant epigenomes, involved in the formation of heterochromatin and affecting gene expression. Extensive variation of DNA methylation patterns within a species has been uncovered from studies of natural variation. However, the extent to which DNA methylation varies between flowering plant species is still unclear. To understand the variation in genomic patterning of DNA methylation across flowering plant species, we compared single base resolution DNA methylomes of 34 diverse angiosperm species. By analyzing whole-genome bisulfite sequencing data in a phylogenetic context, it becomes clear that there is extensive variation throughout angiosperms in gene body DNA methylation, euchromatic silencing of transposons and repeats, as well as silencing of heterochromatic transposons. The Brassicaceae have reduced CHG methylation levels and also reduced or loss of CG gene body methylation. The Poaceae are characterized by a lack or reduction of heterochromatic CHH methylation and enrichment of CHH methylation in genic regions. Furthermore, low levels of CHH methylation are observed in a number of species, especially in clonally propagated species. These results reveal the extent of variation in DNA methylation in angiosperms and show that DNA methylation patterns are broadly a reflection of the evolutionary and life histories of plant species.

Via Andres Zurita, Jennifer Mach
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The auxin response factor MONOPTEROS controls meristem function and organogenesis in both the shoot and root through the direct regulation of PIN genes - Krogan - 2016 - New Phytologist -

The auxin response factor MONOPTEROS controls meristem function and organogenesis in both the shoot and root through the direct regulation of PIN genes - Krogan - 2016 - New Phytologist - | plant molecular biology | Scoop.it
The regulatory effect auxin has on its own transport is critical in numerous self-organizing plant patterning processes. However, our understanding of the molecular mechanisms linking auxin signal transduction and auxin transport is still fragmentary, and important regulatory genes remain to be identified.
To track a key link between auxin signaling and auxin transport in development, we established an Arabidopsis thaliana genetic background in which fundamental patterning processes in both shoot and root were essentially abolished and the expression of PIN FORMED (PIN) auxin efflux facilitators was dramatically reduced.
In this background, we demonstrate that activating a steroid-inducible variant of the auxin response factor (ARF) MONOPTEROS (MP) is sufficient to restore patterning and PIN gene expression. Further, we show that MP binds to distinct promoter elements of multiple genetically defined PIN genes.
Our work identifies a direct regulatory link between central, well-characterized genes involved in auxin signal transduction and auxin transport. The steroid-inducible MP system directly demonstrates the importance of this molecular link in multiple patterning events in embryos, shoots and roots, and provides novel options for interrogating the properties of self-regulated auxin-based patterning in planta.

Via Christophe Jacquet
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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 molecular biology | Scoop.it

Artemisinin-based therapies are the only effective treatment for malaria, the most devastating disease in human history. To meet the growing demand for artemisinin and make it accessible to the poorest, an inexpensive and rapidly scalable production platform is urgently needed. Here we have developed a new synthetic biology approach, combinatorial supertransformation of transplastomic recipient lines (COSTREL), and applied it to introduce the complete pathway for artemisinic acid, the precursor of artemisinin, into the high-biomass crop tobacco. We first introduced the core pathway of artemisinic acid biosynthesis into the chloroplast genome. The transplastomic plants were then combinatorially supertransformed with cassettes for all additional enzymes known to affect flux through the artemisinin pathway. By screening large populations of COSTREL lines, we isolated plants that produce more than 120 milligram artemisinic acid per kilogram biomass. Our work provides an efficient strategy for engineering complex biochemical pathways into plants and optimizing the metabolic output.


Via Pierre-Marc Delaux, Loïc Lepiniec
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Auxin response factors - Chandler - 2016 - Plant, Cell & Environment -

Auxin response factors - Chandler - 2016 - Plant, Cell & Environment - | plant molecular biology | Scoop.it
Auxin signalling involves the activation or repression of gene expression by a class of auxin response factor (ARF) proteins that bind to auxin response elements in auxin-responsive gene promoters. The release of ARF repression in the presence of auxin by the degradation of their cognate auxin/indole-3-acetic acid repressors forms a paradigm of transcriptional response to auxin. However, this mechanism only applies to activating ARFs, and further layers of complexity of ARF function and regulation are being revealed, which partly reflect their highly modular domain structure. This review summarizes our knowledge concerning ARF binding site specificity, homodimer and heterodimer multimeric ARF association and cooperative function and how activator ARFs activate target genes via chromatin remodelling and evolutionary information derived from phylogenetic comparisons from ARFs from diverse species. ARFs are regulated in diverse ways, and their importance in non-auxin-regulated pathways is becoming evident. They are also embedded within higher-order transcription factor complexes that integrate signalling pathways from other hormones and in response to the environment. The ways in which new information concerning ARFs on many levels is causing a revision of existing paradigms of auxin response are discussed.

Via Christophe Jacquet
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A proposed regulatory framework for genome-edited crops : Nature Genetics

A proposed regulatory framework for genome-edited crops : Nature Genetics | plant molecular biology | Scoop.it
Sanwen Huang, Detlef Weigel, Roger Beachy and Jiayang Li propose a regulatory framework for precision breeding with genome-edited crops. They argue that society should benefit from the latest advances in plant genetics and genomics.

Via Loïc Lepiniec
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High-frequency, precise modification of the tomato genome - Genome Biol.

High-frequency, precise modification of the tomato genome - Genome Biol. | plant molecular biology | Scoop.it

(via T. Lahaye, thx)

Čermák et al, 2015

The use of homologous recombination to precisely modify plant genomes has been challenging, due to the lack of efficient methods for delivering DNA repair templates to plant cells. Even with the advent of sequence-specific nucleases, which stimulate homologous recombination at predefined genomic sites by creating targeted DNA double-strand breaks, there are only a handful of studies that report precise editing of endogenous genes in crop plants. More efficient methods are needed to modify plant genomes through homologous recombination, ideally without randomly integrating foreign DNA.


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Non-transgenic Plant Genome Editing Using Purified Sequence-Specific Nucleases: Molecular Plant

Non-transgenic Plant Genome Editing Using Purified Sequence-Specific Nucleases: Molecular Plant | plant molecular biology | Scoop.it

(via J. Boch, thx)

Luo et al, 2015

Sequence-specific nucleases, including zinc-finger nucleases, meganucleases, TAL effector nucleases (TALENs), and CRISPR/Cas systems, have been used to introduce targeted mutations in a wide range of plant species (Voytas, 2013; Baltes and Voytas, 2015). However, delivery of these nucleases using traditional transformation methods (e.g., particle bombardment, Agrobacterium or protoplast transformation) may result in undesired genetic alterations due to random insertion of nuclease-encoding DNA into the host genome.


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A tomato phloem-mobile protein regulates the shoot-to-root ratio by mediating the auxin response in distant organs - Spiegelman - 2015 - The Plant Journal - Wiley Online Library

A tomato phloem-mobile protein regulates the shoot-to-root ratio by mediating the auxin response in distant organs - Spiegelman - 2015 - The Plant Journal - Wiley Online Library | plant molecular biology | Scoop.it
The plant vascular system serves as a conduit for delivery of both nutrients and signaling molecules to various distantly located organs. The anucleate sieve tube system of the angiosperm phloem delivers sugars and amino acids to developing organs, and has recently been shown to contain a unique population of RNA and proteins. Grafting studies have established that a number of these macromolecules are capable of moving long distances between tissues, thus providing support for operation of a phloem-mediated inter-organ communication network. Currently, our knowledge of the roles played by such phloem-borne macromolecules is in its infancy. Here, we show that, in tomato, translocation of a phloem-mobile cyclophilin, SlCyp1, from a wild-type scion into a mutant rootstock results in restoration of vascular development and lateral root initiation. This process occurs through reactivation of auxin response pathways and reprogramming of the root transcriptome. Moreover, we show that long-distance trafficking of SlCyp1 is associated with regulation of the shoot-to-root ratio in response to changing light intensities, by modulating root growth. We conclude that long-distance trafficking of SlCyp1 acts as a rheostat to control the shoot-to-root ratio, by mediating root development to integrate photosynthesis and light intensity with requirements for access to water and mineral nutrients.

Via Christophe Jacquet
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Team pinpoints genes that make plant stem cells, revealing origin of beefsteak tomatoes

Team pinpoints genes that make plant stem cells, revealing origin of beefsteak tomatoes | plant molecular biology | Scoop.it
A team of scientists at Cold Spring Harbor Laboratory has identified a set of genes that control stem cell production in tomato. Mutations in these genes explain the origin of mammoth beefsteak tomatoes. More important, the research suggests how breeders can optimize fruit size in potentially any fruit-bearing crop.

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Auxin Import and Local Auxin Biosynthesis Are Required for Mitotic Divisions, Cell Expansion and Cell Specification during Female Gametophyte Development in Arabidopsis thaliana

Auxin Import and Local Auxin Biosynthesis Are Required for Mitotic Divisions, Cell Expansion and Cell Specification during Female Gametophyte Development in Arabidopsis thaliana | plant molecular biology | Scoop.it

The female gametophyte of flowering plants, called the embryo sac, develops from a haploid cell named the functional megaspore, which is specified after meiosis by the diploid sporophyte. In Arabidopsis, the functional megaspore undergoes three syncitial mitotic divisions followed by cellularization to form seven cells of four cell types including two female gametes. The plant hormone auxin is important for sporophytic developmental processes, and auxin levels are known to be regulated by biosynthesis and transport. Here, we investigated the role of auxin biosynthetic genes and auxin influx carriers in embryo sac development. We find that genes from the YUCCA/TAA pathway (YUC1, YUC2, YUC8, TAA1, TAR2) are expressed asymmetrically in the developing ovule and embryo sac from the two-nuclear syncitial stage until cellularization. Mutants for YUC1 and YUC2 exhibited defects in cell specification, whereas mutations in YUC8, as well as mutations in TAA1 and TAR2, caused defects in nuclear proliferation, vacuole formation and anisotropic growth of the embryo sac. Additionally, expression of the auxin influx carriers AUX1 and LAX1 were observed at the micropylar pole of the embryo sac and in the adjacent cells of the ovule, and the aux1 lax1 lax2 triple mutant shows multiple gametophyte defects. These results indicate that both localized auxin biosynthesis and auxin import, are required for mitotic divisions, cell expansion and patterning during embryo sac development.


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New tangles in the auxin signaling web - F1000Prime Reports

New tangles in the auxin signaling web - F1000Prime Reports | plant molecular biology | Scoop.it
Plants use auxin to relay critical information that shapes their growth and development. Auxin perception and transcriptional activation are mediated by the degradation of Aux/IAA repressor proteins. Degradation of Aux/IAAs relieves repression on Auxin Response Factors (ARFs), which bind DNA sequences called Auxin Response Elements (AuxREs). In most higher plant genomes, multiple paralogs exist for each part of the auxin nuclear signaling pathway. This potential combinatorial diversity in signaling pathways likely contributes to the myriad of context-specific responses to auxin. Recent structures of several domains from ARF proteins have exposed new modes of ARF dimerization, new models for ARF-AuxRE specificity, and the strong likelihood of larger order complexes formed by ARF and Aux/IAA homo- and heteromultimerization. Preliminary experiments support a role for these novel interactions in planta, further increasing the potential architectural complexity of this seemingly simple pathway.

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Auxin binding protein 1 (ABP1) is not required for either auxin signaling or Arabidopsis development

Auxin binding protein 1 (ABP1) is not required for either auxin signaling or Arabidopsis development | plant molecular biology | Scoop.it
Auxin binding protein 1 (ABP1) has been studied for decades. It has been suggested that ABP1 functions as an auxin receptor and has an essential role in many developmental processes. Here we present our unexpected findings that ABP1 is neither required for auxin signaling nor necessary for plant development under normal growth conditions. We used our ribozyme-based CRISPR technology to generate an Arabidopsis abp1 mutant that contains a 5-bp deletion in the first exon of ABP1, which resulted in a frameshift and introduction of early stop codons. We also identified a T-DNA insertion abp1 allele that harbors a T-DNA insertion located 27 bp downstream of the ATG start codon in the first exon. We show that the two new abp1 mutants are null alleles. Surprisingly, our new abp1 mutant plants do not display any obvious developmental defects. In fact, the mutant plants are indistinguishable from wild-type plants at every developmental stage analyzed. Furthermore, the abp1 plants are not resistant to exogenous auxin. At the molecular level, we find that the induction of known auxin-regulated genes is similar in both wild-type and abp1 plants in response to auxin treatments. We conclude that ABP1 is not a key component in auxin signaling or Arabidopsis development.

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