Emerging Research...
Follow
Find
8.0K views | +20 today
Rescooped by Jennifer Mach from PlantBioInnovation
onto Emerging Research in Plant Cell Biology
Scoop.it!

Unusual Case of Apparent Hypermutation in Arabidopsis thaliana

The dms4 (defective in meristem silencing 4) mutant of Arabidopsis thaliana is unique in having defects in both RNA-directed DNA methylation (RdDM) and plant development. DMS4 is an evolutionarily conserved, putative transcription factor of the Iwr1 (interacts with RNA polymerase II) type. DMS4 interacts with Pol II and also with RNA polymerases IV and V, which function in RdDM. Interactions with multiple polymerases may account for the diverse phenotypic effects of dms4 mutations. To dissect further the roles of DMS4 in RdDM and development, we performed a genetic suppressor screen using the dms4-1 allele, which contains in the sixth intron a splice site acceptor mutation that alters splicing and destroys the open reading frame. Following mutagenesis of dms4-1 seeds using ethyl methanesulfonate (EMS), we retrieved four dominant intragenic suppressor mutations that restored DMS4 function and wild-type phenotypes. Three of the four intragenic suppressor mutations created new splice site acceptors, which resulted in reestablishment of the wild-type open reading frame. Remarkably, the intragenic suppressor mutations were recovered at frequencies ranging from 35 to 150 times higher than expected for standard EMS mutagenesis in Arabidopsis. Whole-genome sequencing did not reveal an elevated mutation frequency genome-wide, indicating that the apparent hypermutation was confined to four specific sites in the dms4 gene. The localized high mutation frequency correlated with restoration of DMS4 function implies an efficient mechanism for targeted mutagenesis or selection of more fit revertant cells in the shoot apical meristem, thereby rapidly restoring a wild-type phenotype that is transmitted to future generations.


Via Biswapriya Biswavas Misra
more...
No comment yet.
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
Your new post is loading...
Rescooped by Jennifer Mach from Plant-Microbe Symbioses
Scoop.it!

Host plant and arbuscular mycorrhizal fungi show contrasting responses to temperature increase: Implications for dioecious plants

Host plant and arbuscular mycorrhizal fungi show contrasting responses to temperature increase: Implications for dioecious plants | Emerging Research in Plant Cell Biology | Scoop.it

Individual plants live in complex environments where they interact with other organisms such as herbivores, pollinators, fungi and pathogens. The influence of rising temperature on biotic interactions has begun to receive attention, and is an important research frontier currently. However, the belowground interactions with organisms such as arbuscular mycorrhizal (AM) fungi have received little attention so far. In this study, we investigated the response of the dioecious plant Antennaria dioica and its AM fungi to increased temperature in a controlled environment simulating the period of growth of A. dioica in central Finland. Specifically, we evaluated the effect of rising temperature on plant survival, growth, flowering and physiology in plants growing with or without AM fungi. Overall, increased temperature had a positive effect on plant survival, but a negative effect on the growth and flowering compared with the control temperature, while it did not affect the physiological parameters analyzed. Females suffered more of rising temperature in terms of reduced flowering, but a larger proportion of plants survived compared to males. In contrast, the rising temperature had positive effects on the frequency of AM fungal colonization in roots regardless of sex, but sex-specific differences were observed in the amount of extraradical hyphae and the number of spores produced. These findings suggest than the sexes in dioecious species and their associated fungi respond differently to increasing temperature. If rising temperature affects host plants and symbionts in a contrasting way, a potential functional mismatch might appear.


Via Jean-Michel Ané
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

ACTIN-RELATED PROTEIN6 Regulates Female Meiosis By Modulating Meiotic Gene Expression in Arabidopsis

ACTIN-RELATED PROTEIN6 Regulates Female Meiosis By Modulating Meiotic Gene Expression in Arabidopsis | Emerging Research in Plant Cell Biology | Scoop.it

In flowering plants, meiocytes develop from subepidermal cells in anthers and ovules. The mechanisms that integrate gene-regulatory processes with meiotic programs during reproductive development remain poorly characterized. Here, we show that Arabidopsis thaliana plants deficient in ACTIN-RELATED PROTEIN6 (ARP6), a subunit of the SWR1 ATP-dependent chromatin-remodeling complex, exhibit defects in prophase I of female meiosis. We found that this meiotic defect is likely due to dysregulated expression of meiotic genes, particularly those involved in meiotic recombination, including DMC1 (DISRUPTED MEIOTIC cDNA1). Analysis of DMC1 expression in arp6 mutant plants indicated that ARP6 inhibits expression of DMC1 in the megasporocyte and surrounding nonsporogeneous ovule cells before meiosis. After cells enter meiosis, however, ARP6 activatesDMC1 expression specifically in the megasporocyte even as it continues to inhibitDMC1 expression in the nonsporogenous ovule cells. We further show that deposition of the histone variant H2A.Z, mediated by the SWR1 chromatin-remodeling complex at the DMC1 gene body, requires ARP6. Therefore, ARP6 regulates female meiosis by determining the spatial and temporal patterns of gene expression required for proper meiosis during ovule development.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Three Groups of Transposable Elements with Contrasting Copy Number Dynamics and Host Responses in the Maize (Zea mays ssp. mays) Genome

Three Groups of Transposable Elements with Contrasting Copy Number Dynamics and Host Responses in the Maize (Zea mays ssp. mays) Genome | Emerging Research in Plant Cell Biology | Scoop.it

Most angiosperm nuclear DNA is repetitive and derived from silenced transposable elements (TEs). TE silencing requires substantial resources from the plant host, including the production of small interfering RNAs (siRNAs). Thus, the interaction between TEs and siRNAs is a critical aspect of both the function and the evolution of plant genomes. Yet the co-evolutionary dynamics between these two entities remain poorly characterized. Here we studied the organization of TEs within the maize (Zea mays ssp mays) genome, documenting that TEs fall within three groups based on the class and copy numbers. These groups included DNA elements, low copy RNA elements and higher copy RNA elements. The three groups varied statistically in characteristics that included length, location, age, siRNA expression and 24:22 nucleotide (nt) siRNA targeting ratios. In addition, the low copy retroelements encompassed a set of TEs that had previously been shown to decrease expression within a 24 nt siRNA biogenesis mutant (mop1). To investigate the evolutionary dynamics of the three groups, we estimated their abundance in two landraces, one with a genome similar in size to that of the maize reference and the other with a 30% larger genome. For all three accessions, we assessed TE abundance as well as 22 nt and 24 nt siRNA content within leaves. The high copy number retroelements are under targeted similarly by siRNAs among accessions, appear to be born of a rapid bust of activity, and may be currently transpositionally dead or limited. In contrast, the lower copy number group of retrolements are targeted more dynamically and have had a long and ongoing history of transposition in the maize genome.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Structural Basis for Assembly and Function of a Heterodimeric Plant Immune Receptor

Cytoplasmic plant immune receptors recognize specific pathogen effector proteins and initiate effector-triggered immunity. In Arabidopsis, the immune receptors RPS4 and RRS1 are both required to activate defense to three different pathogens. We show that RPS4 and RRS1 physically associate. Crystal structures of the N-terminal Toll–interleukin-1 receptor/resistance (TIR) domains of RPS4 and RRS1, individually and as a heterodimeric complex (respectively at 2.05, 1.75, and 2.65 angstrom resolution), reveal a conserved TIR/TIR interaction interface. We show that TIR domain heterodimerization is required to form a functional RRS1/RPS4 effector recognition complex. The RPS4 TIR domain activates effector-independent defense, which is inhibited by the RRS1 TIR domain through the heterodimerization interface. Thus, RPS4 and RRS1 function as a receptor complex in which the two components play distinct roles in recognition and signaling.

Jennifer Mach's insight:

And a perspective:

http://www.sciencemag.org/content/344/6181/267.summary

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Plastid genomes — lost in translation?

Plastid genomes — lost in translation? | Emerging Research in Plant Cell Biology | Scoop.it

Many eukaryotic lineages have lost the ability to photosynthesize but have retained plastids — membrane-bound organelles that typically contain a small DNA genome — that continue to carry out metabolic functions. Researchers have previously suggested that the plastid genome is essential because it has been widely preserved. However, two separate studies now provide evidence f…

Jennifer Mach's insight:

Nature Reviews Genetics brings together two papers on plastid genome loss; original papers here:

http://www.plantphysiol.org/content/164/4/1812

http://mbe.oxfordjournals.org/content/31/4/793

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

A first genetic map of date palm (Phoenix dactylifera) reveals long-range genome structure conservation in the palms

A first genetic map of date palm (Phoenix dactylifera) reveals long-range genome structure conservation in the palms | Emerging Research in Plant Cell Biology | Scoop.it
The date palm is one of the oldest cultivated fruit trees. It is critical in many ways to cultures in arid lands by providing highly nutritious fruit while surviving extreme heat and environmental conditions. Despite its importance from antiquity, few genetic resources are available for improving the productivity and development of the dioecious date palm. To date there has been no genetic map and no sex chromosome has been identified.
more...
No comment yet.
Rescooped by Jennifer Mach from Plant Pathogenomics
Scoop.it!

PLOS Genetics: Interspecific Sex in Grass Smuts and the Genetic Diversity of Their Pheromone-Receptor System (2011)

PLOS Genetics: Interspecific Sex in Grass Smuts and the Genetic Diversity of Their Pheromone-Receptor System (2011) | Emerging Research in Plant Cell Biology | Scoop.it

The grass smuts comprise a speciose group of biotrophic plant parasites, so-called Ustilaginaceae, which are specifically adapted to hosts of sweet grasses, the Poaceae family. Mating takes a central role in their life cycle, as it initiates parasitism by a morphological and physiological transition from saprobic yeast cells to pathogenic filaments. As in other fungi, sexual identity is determined by specific genomic regions encoding allelic variants of a pheromone-receptor (PR) system and heterodimerising transcription factors. Both operate in a biphasic mating process that starts with PR–triggered recognition, directed growth of conjugation hyphae, and plasmogamy of compatible mating partners. So far, studies on the PR system of grass smuts revealed diverse interspecific compatibility and mating type determination. However, many questions concerning the specificity and evolutionary origin of the PR system remain unanswered. Combining comparative genetics and biological approaches, we report on the specificity of the PR system and its genetic diversity in 10 species spanning about 100 million years of mating type evolution. We show that three highly syntenic PR alleles are prevalent among members of the Ustilaginaceae, favouring a triallelic determination as the plesiomorphic characteristic of this group. Furthermore, the analysis of PR loci revealed increased genetic diversity of single PR locus genes compared to genes of flanking regions. Performing interspecies sex tests, we detected a high potential for hybridisation that is directly linked to pheromone signalling as known from intraspecies sex. Although the PR system seems to be optimised for intraspecific compatibility, the observed functional plasticity of the PR system increases the potential for interspecific sex, which might allow the hybrid-based genesis of newly combined host specificities.


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns

Ferns are well known for their shade-dwelling habits. Their ability to thrive under low-light conditions has been linked to the evolution of a novel chimeric photoreceptor—neochrome—that fuses red-sensing phytochrome and blue-sensing phototropin modules into a single gene, thereby optimizing phototropic responses. Despite being implicated in facilitating the diversification of modern ferns, the origin of neochrome has remained a mystery. We present evidence for neochrome in hornworts (a bryophyte lineage) and demonstrate that ferns acquired neochrome from hornworts via horizontal gene transfer (HGT). Fern neochromes are nested within hornwort neochromes in our large-scale phylogenetic reconstructions of phototropin and phytochrome gene families. Divergence date estimates further support the HGT hypothesis, with fern and hornwort neochromes diverging 179 Mya, long after the split between the two plant lineages (at least 400 Mya). By analyzing the draft genome of the hornwort Anthoceros punctatus, we also discovered a previously unidentified phototropin gene that likely represents the ancestral lineage of the neochrome phototropin module. Thus, a neochrome originating in hornworts was transferred horizontally to ferns, where it may have played a significant role in the diversification of modern ferns.

more...
No comment yet.
Rescooped by Jennifer Mach from MycorWeb Plant-Microbe Interactions
Scoop.it!

New Phytologist: Virtual Special Issue on phytopathogen effector proteins (2014)

New Phytologist: Virtual Special Issue on phytopathogen effector proteins (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Upon analysis of phytopathogen genomes it turned out that phytopathogenic microbes typically express dozens (bacteria; Collmer et al., 2009) to hundreds (oomycetes and fungi; Schmidt & Panstruga, 2011) of effector proteins. They often do not share any considerable sequence relatedness to known proteins and therefore can be considered as ‘pioneer proteins’, which renders their functional analysis a formidable task. Nevertheless, owing to the key role effector proteins play in plant–microbe interactions, their molecular analysis lately became very popular and is a flourishing research field. This development, which is evidenced by the substantial increase in literature devoted to ‘effectors’ during the last decade (Fig. 1), has also been appreciated by New Phytologist as documented by the organization of two symposia, in 2009 and 2012, with an emphasis on effectors in plant–microbe interactions (22nd New Phytologist Symposium and 30th New Phytologist Symposium; Lee et al., 2013). Besides proteinaceous effectors, secreted small molecules can also exhibit effector activity. Prominent examples from the phytopathogenic bacterium Pseudomonas syringae comprise syringolin (a proteasome inhibitor) and coronatine (a mimic of the phytohormone jasmonic acid), but also fungal secondary metabolites can have defense-suppressing activities (e.g. host-selective toxins; Tsuge et al., 2013).

 

In this Virtual Special Issue we compile a number of papers that were published recently in New Phytologist which all deal with various aspects of effector biology, ranging from bacterial to oomycete and fungal as well as nematode effectors. These papers cover effector functions related to suppression of plant immune responses as well as nutrient acquisition and the identification of plant effector targets.


Via Kamoun Lab @ TSL, Francis Martin
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Boom-Bust Turnovers of Megabase-Sized Centromeric DNA in Solanum Species: Rapid Evolution of DNA Sequences Associated with Centromeres

Boom-Bust Turnovers of Megabase-Sized Centromeric DNA in Solanum Species: Rapid Evolution of DNA Sequences Associated with Centromeres | Emerging Research in Plant Cell Biology | Scoop.it

Centromeres are composed of long arrays of satellite repeats in most multicellular eukaryotes investigated to date. The satellite repeat–based centromeres are believed to have evolved from “neocentromeres” that originally contained only single- or low-copy sequences. However, the emergence and evolution of the satellite repeats in centromeres has been elusive. Potato (Solanum tuberosum) provides a model system for studying centromere evolution because each of its 12 centromeres contains distinct DNA sequences, allowing comparative analysis of homoeologous centromeres from related species. We conducted genome-wide analysis of the centromeric sequences in Solanum verrucosum, a wild species closely related to potato. Unambiguous homoeologous centromeric sequences were detected in only a single centromere (Cen9) between the two species. Four centromeres (Cen2, Cen4, Cen7, and Cen10) in S. verrucosum contained distinct satellite repeats that were amplified from retrotransposon-related sequences. Strikingly, the same four centromeres in potato contain either different satellite repeats (Cen2 and Cen7) or exclusively single- and low-copy sequences (Cen4 and Cen10). Our sequence comparison of five homoeologous centromeres in two Solanum species reveals rapid divergence of centromeric sequences among closely related species. We propose that centromeric satellite repeats undergo boom-bust cycles before a favorable repeat is fixed in the population.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

A restorer-of-fertility like pentatricopeptide repeat gene directs ribonucleolytic processing within the coding sequence of rps3-rpl16 and orf240a mitochondrial transcripts in Arabidopsis thaliana ...

A restorer-of-fertility like pentatricopeptide repeat gene directs ribonucleolytic processing within the coding sequence of rps3-rpl16 and orf240a mitochondrial transcripts in Arabidopsis thaliana ... | Emerging Research in Plant Cell Biology | Scoop.it

The pentatricopeptide repeat (PPR) proteins represent a large family of RNA-binding proteins that have many roles in post-transcriptional RNA processes within plant organelles. Among the PPR proteins that target plant mitochondria, the restorer-of-fertility (Rf) proteins are characterized by their inhibitory action on mitochondrion-localized cytoplasmic male sterility (CMS) genes in various crop species. Close homologs to known Rfs from radish, petunia, and rice can be identified in most higher plant species and these proteins define the recognized subgroup of Rf-like (RFL) PPR proteins. In this paper we describe the function of the RFL9 gene from Arabidopsis thaliana, and show that it is associated with ribonucleolytic cleavages within the coding sequences of rps3-rpl16 and orf240a mitochondrial transcripts in the Col-0 accession. RFL9 therefore represents an Rf-like PPR gene that has the potential to compromise the function of an essential mitochondrial gene and whose function is also associated with a mitochondrial orf sharing significant homology with a proven CMS-causing orf. We observe that RFL9 is active in only a few Arabidopsis accessions genetically close to Col-0, which supports the idea that the genetic fixation of this gene represents a regional event in the recent evolution of Arabidopsis. Additionally, RFL9 counts among theRFL genes that are probably controlled by short regulatory RNAs, and our results provides a potential explanation for such control, which in the case of RFL9 might have evolved to limit its detrimental effect on rps3 expression.

Jennifer Mach's insight:

A very interesting PRR protein!

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Transcript residency on ribosomes reveals a key role for the Arabidopsis thaliana bundle sheath in sulphur and glucosinolate metabolism

Transcript residency on ribosomes reveals a key role for the Arabidopsis thaliana bundle sheath in sulphur and glucosinolate metabolism | Emerging Research in Plant Cell Biology | Scoop.it

Leaves of angiosperms are made up of multiple distinct cell types. While the function of mesophyll cells, guard cells, phloem companion cells and sieve elements are clearly described, this is not the case for the bundle sheath (BS). To provide insight into the role of the BS in the C3 species Arabidopsis thaliana, we labelled ribosomes in this cell type with a FLAG tag. We then used immunocapture to isolate these ribosomes followed by sequencing of resident mRNAs. This showed that 5% of genes showed specific splice forms in the BS, and that 15% of genes were preferentially expressed in these cells. The BS translatome strongly implicates the BS in specific roles in sulphur transport and metabolism, glucosinolate biosynthesis and trehalose metabolism. Much of the C4 cycle is differentially expressed between the C3 BS and the rest of the leaf. Furthermore, the global patterns of transcript residency on BS ribosomes overlap to a greater extent with cells of the root pericycle than any other cell type. This analysis provides the first insight into the molecular function of this cell type in C3 species, and also identifies characteristics of BS cells that are likely ancestral to both C3 and C4 plants.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

A Chloroplast Retrograde Signal Regulates Nuclear Alternative Splicing

Light is a source of energy and also a regulator of plant physiological adaptations. We show here that light/dark conditions affect alternative splicing of a subset of Arabidopsis genes preferentially encoding proteins involved in RNA processing. The effect requires functional chloroplasts and is also observed in roots when the communication with the photosynthetic tissues is not interrupted, suggesting that a signaling molecule travels through the plant. Using photosynthetic electron transfer inhibitors with different mechanisms of action, we deduce that the reduced pool of plastoquinones initiates a chloroplast retrograde signaling that regulates nuclear alternative splicing and is necessary for proper plant responses to varying light conditions.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Homoeologous Chromosome Sorting and Progression of Meiotic Recombination in Brassica napus: Ploidy Does Matter!

Homoeologous Chromosome Sorting and Progression of Meiotic Recombination in Brassica napus: Ploidy Does Matter! | Emerging Research in Plant Cell Biology | Scoop.it

Meiotic recombination is the fundamental process that produces balanced gametes and generates diversity within species. For successful meiosis, crossovers must form between homologous chromosomes. This condition is more difficult to fulfill in allopolyploid species, which have more than two sets of related chromosomes (homoeologs). Here, we investigated the formation, progression, and completion of several key hallmarks of meiosis in Brassica napus (AACC), a young polyphyletic allotetraploid crop species with closely related homoeologous chromosomes. Altogether, our results demonstrate a precocious and efficient sorting of homologous versus homoeologous chromosomes during early prophase I in two representative B. napus accessions that otherwise show a genotypic difference in the progression of homologous recombination. More strikingly, our detailed comparison of meiosis in near isogenic allohaploid and euploid plants showed that the mechanism(s) promoting efficient chromosome sorting in euploids is adjusted to promote crossover formation between homoeologs in allohaploids. This suggests that, in contrast to other polyploid species, chromosome sorting is context dependent in B. napus.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism | Emerging Research in Plant Cell Biology | Scoop.it

Nitrogen (N) is a key nutrient that limits global primary productivity; hence, N-use efficiency is of compelling interest in agriculture and aquaculture. We usedChlamydomonas reinhardtii as a reference organism for a multicomponent analysis of the N starvation response. In the presence of acetate, respiratory metabolism is prioritized over photosynthesis; consequently, the N-sparing response targets proteins, pigments, and RNAs involved in photosynthesis and chloroplast function over those involved in respiration. Transcripts and proteins of the Calvin-Benson cycle are reduced in N-deficient cells, resulting in the accumulation of cycle metabolic intermediates. Both cytosolic and chloroplast ribosomes are reduced, but via different mechanisms, reflected by rapid changes in abundance of RNAs encoding chloroplast ribosomal proteins but not cytosolic ones. RNAs encoding transporters and enzymes for metabolizing alternative N sources increase in abundance, as is appropriate for the soil environmental niche of C. reinhardtii. Comparison of the N-replete versus N-deplete proteome indicated that abundant proteins with a high N content are reduced in N-starved cells, while the proteins that are increased have lower than average N contents. This sparing mechanism contributes to a lower cellular N/C ratio and suggests an approach for engineering increased N-use efficiency.

Jennifer Mach's insight:

An In Brief summary too!

http://www.plantcell.org/content/early/2014/04/18/tpc.114.126334.full.pdf

more...
No comment yet.
Rescooped by Jennifer Mach from TAL effector science
Scoop.it!

Precision genetic modifications: a new era in molecular biology and crop improvement - Planta

Precision genetic modifications: a new era in molecular biology and crop improvement - Planta | Emerging Research in Plant Cell Biology | Scoop.it

(via T. Schreiber, thx)

Fichtner et al, 2014

Recently, the use of programmable DNA-binding proteins such as ZFP/ZFNs, TALE/TALENs and CRISPR/Cas has produced unprecedented advances in gene targeting and genome editing in prokaryotes and eukaryotes. These advances allow researchers to specifically alter genes, reprogram epigenetic marks, generate site-specific deletions and potentially cure diseases. Unlike previous methods, these precision genetic modification techniques (PGMs) are specific, efficient, easy to use and economical. Here we discuss the capabilities and pitfalls of PGMs and highlight the recent, exciting applications of PGMs in molecular biology and crop genetic engineering. Further improvement of the efficiency and precision of PGM techniques will enable researchers to precisely alter gene expression and biological/chemical pathways, probe gene function, modify epigenetic marks and improve crops by increasing yield, quality and tolerance to limiting biotic and abiotic stress conditions.


Via dromius
more...
dromius's curator insight, February 8, 5:45 AM

very nice comparative review from the Uelker lab!

Rescooped by Jennifer Mach from Plants and Microbes
Scoop.it!

Figshare: Agrobacterium tumefaciens does not transform guard cells in Nicotiana benthamiana (2014)

Figshare: Agrobacterium tumefaciens does not transform guard cells in Nicotiana benthamiana (2014) | Emerging Research in Plant Cell Biology | Scoop.it

The bacterium Agrobacterium tumefaciens is widely used to genetically transform leaf cells of Nicotiana benthamiana using the agroinfiltration method. Interestingly, A. tumefaciens does not transform guard cells, whereas it transforms efficiently pavement cells. The high chlorophyll content makes chloroplasts autofluorescent. In the case of live-cell imaging experiments with leaf cells transiently expressing fluorescent markers targeted to chloroplasts, it is hard to differentiate the fluorescent marker signal from chlorophyll autofluorescence. Here, I show that guard cells can be used to differentiate those. A GFP targeted to the chloroplast stroma was transiently expressed in N. benthamiana leaf cells, and epidermis cells were observed by live-cell imaging with a laser-scanning confocal microscope two days after the agro-infiltration. A 488 nm wavelength was used to illuminate the tissues, and GFP and chlorophyll signals were collected between 505-525 nm and 680-700 nm, respectively. The asterisks mark the guard cells, the cross marks a non-transformed pavement cell. The white rectangle on the merged image delimitates the close-ups presented in the lower panel. Note the absence of GFP signal in chloroplasts from the guard cells and from the non-transformed pavement cell.


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Predicting biodiversity change and averting collapse in agricultural landscapes

Predicting biodiversity change and averting collapse in agricultural landscapes | Emerging Research in Plant Cell Biology | Scoop.it

The equilibrium theory of island biogeography1 is the basis for estimating extinction rates2 and a pillar of conservation science3, 4. The default strategy for conserving biodiversity is the designation of nature reserves, treated as islands in an inhospitable sea of human activity5. Despite the profound influence of islands on conservation theory and practice3, 4, their mainland analogues, forest fragments in human-dominated landscapes, consistently defy expected biodiversity patterns based on island biogeography theory6, 7, 8, 9, 10, 11, 12, 13. Countryside biogeography is an alternative framework, which recognizes that the fate of the world’s wildlife will be decided largely by the hospitality of agricultural or countryside ecosystems12, 14, 15, 16, 17. Here we directly test these biogeographic theories by comparing a Neotropical countryside ecosystem with a nearby island ecosystem, and show that each supports similar bat biodiversity in fundamentally different ways. The island ecosystem conforms to island biogeographic predictions of bat species loss, in which the water matrix is not habitat. In contrast, the countryside ecosystem has high species richness and evenness across forest reserves and smaller forest fragments. Relative to forest reserves and fragments, deforested countryside habitat supports a less species-rich, yet equally even, bat assemblage. Moreover, the bat assemblage associated with deforested habitat is compositionally novel because of predictable changes in abundances by many species using human-made habitat. Finally, we perform a global meta-analysis of bat biogeographic studies, spanning more than 700 species. It generalizes our findings, showing that separate biogeographic theories for countryside and island ecosystems are necessary. A theory of countryside biogeography is essential to conservation strategy in the agricultural ecosystems that comprise roughly half of the global land surface and are likely to increase even further14.

more...
No comment yet.
Rescooped by Jennifer Mach from MycorWeb Plant-Microbe Interactions
Scoop.it!

Transcription factor-dependent nuclear localization of a transcriptional repressor in jasmonate hormone signaling

Transcription factor-dependent nuclear localization of a transcriptional repressor in jasmonate hormone signaling | Emerging Research in Plant Cell Biology | Scoop.it

The plant hormone jasmonate (JA) plays an important role in regulating growth, development and immunity. A key step in JA signaling is ligand-dependent assembly of a coreceptor complex consisting of the F-box protein COI1 and JAZ transcriptional repressors. Assembly of this receptor complex results in proteasome-mediated degradation of JAZ repressors, which at resting state bind to and repress the MYC transcription factors. Although the JA receptor complex is believed to function within the nucleus, how this receptor complex enters the nucleus and, more generally, the cell biology of jasmonate signaling are not well understood. In this study, we conducted mutational analysis of the C termini (containing the conserved Jas motif) of two JAZ repressors, JAZ1 and JAZ9. These analyses unexpectedly revealed different subcellular localization patterns of JAZ1ΔJas and JAZ9ΔJas, which were associated with differential interaction of JAZ1ΔJas and JAZ9ΔJas with MYC2 and differential repressor activity in vivo. Importantly, physical interaction with MYC2 appears to play an active role in the nuclear targeting of JAZ1 and JAZ9, and the nuclear localization of JAZ9 was compromised in myc2 mutant plants. We identified a highly conserved arginine residue in the Jas motif that is critical for coupling MYC2 interaction with nuclear localization of JAZ9 and JAZ9 repressor function in vivo. Our results suggest a model for explaining why some JAZΔJas proteins, but not others, confer constitutive JA-insensitivity when overexpressed in plants. Results also provide evidence for a transcription factor-dependent mechanism for nuclear import of a cognate transcriptional repressor JAZ9 in plants.


Via Francis Martin
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Plant biologists FRET over stress

Plant biologists FRET over stress | Emerging Research in Plant Cell Biology | Scoop.it

For a plant, the world is full of stress. There are unpredictable rains, freezing winters and baking hot summers. Plants can deal with these insults by detecting when they happen, and then using a suite of hormones to control their own growth and physiology to minimise, or counteract, any damage that might occur. One of the major plant hormones that is involved in the responses to stress, such as drought and heat, is abscisic acid (Hauser et al., 2011). However, monitoring the dynamics of this hormone in living plants, especially at the level of individual cells, had proved very challenging....

Jennifer Mach's insight:

This mini-review (with cute "fret" pun) highlights two articles on applications of FRET to imaging ABA in plants:

http://elifesciences.org/content/3/e01741

http://elifesciences.org/content/3/e01739

 

 

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Drought-tolerant varieties begin global march

Drought-tolerant varieties begin global march | Emerging Research in Plant Cell Biology | Scoop.it

175.2 million hectares of biotech crops were grown globally in 2013. In the United States, the first commercialized drought-tolerant maize (MON87460) expressing Bacillus subtilis cold shock protein B (cspB) was planted by 2,000 farmers over 50,000 hectares. Indonesia also approved drought-tolerant sugarcane expressing choline dehydrogenase (betA), which accumulates membrane-protectant glycine…

Jennifer Mach's insight:

"Global march" seems a bit military, but really these are the traits that will save agriculture from the grim future of climate change.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Plasma Membranes Are Subcompartmentalized into a Plethora of Coexisting and Diverse Microdomains in Arabidopsis and Nicotiana benthamiana

Plasma Membranes Are Subcompartmentalized into a Plethora of Coexisting and Diverse Microdomains in Arabidopsis and Nicotiana benthamiana | Emerging Research in Plant Cell Biology | Scoop.it

Eukaryotic plasma membranes are highly compartmentalized structures. So far, only a few individual proteins that function in a wide range of cellular processes have been shown to segregate into microdomains. However, the biological roles of most microdomain-associated proteins are unknown. Here, we investigated the heterogeneity of distinct microdomains and the complexity of their coexistence. This diversity was determined in living cells of intact multicellular tissues using 20 different marker proteins from Arabidopsis thaliana, mostly belonging to the Remorin protein family. These proteins associate with microdomains at the cytosolic leaflet of the plasma membrane. We characterized these membrane domains and determined their lateral dynamics by extensive quantitative image analysis. Systematic colocalization experiments with an extended subset of marker proteins tested in 45 different combinations revealed the coexistence of highly distinct membrane domains on individual cell surfaces. These data provide valuable tools to study the lateral segregation of membrane proteins and their biological functions in living plant cells. They also demonstrate that widely used biochemical approaches such as detergent-resistant membranes cannot resolve this biological complexity of membrane compartmentalization in vivo.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

The Tomato spotted wilt virus cell-to-cell movement protein (NSM) triggers a hypersensitive response in Sw-5 containing resistant tomato lines and Nicotiana benthamiana transformed with the functio...

The Tomato spotted wilt virus cell-to-cell movement protein (NSM) triggers a hypersensitive response in Sw-5 containing resistant tomato lines and Nicotiana benthamiana transformed with the functio... | Emerging Research in Plant Cell Biology | Scoop.it

Although the Sw-5 gene cluster has already been cloned, and Sw-5b identified as the functional gene copy that confers resistance toTomato spotted wilt virus (TSWV), its avirulence (Avr)-determinant still has not been identified. Whereas Nicotiana tabacum ‘SR1’ plants transformed with a copy of Sw-5b gene were immune without producing a clear visual response upon challenging with TSWV, it is here shown that N. bethamiana transformed with Sw-5b gives a rapid and conspicuous hypersensitive response (HR). Using these plants, from all structural and non-structural TSWV proteins tested, the TSWV cell-to-cell movement protein (NSM) was confirmed as the Avr-determinant using a PVX-replicon or a non-replicative, pEAQ-HT expression vector system. HR was induced in Sw-5b-transgenic N. benthamiana as well as in resistant tomato near-isogenic lines after agroinfiltration with a functional cell-to-cell movement protein (NSM) from a resistance inducing (RI) TSWV strain (BR-01), but not with NSM from a Sw-5-resistance breaking (RB) strain (GRAU). This is the first biological demonstration that Sw-5 mediated-resistance is triggered by the TSWV NSM cell-to-cell movement protein.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Revealing insect herbivory-induced phenolamide metabolism: from single genes to metabolic network plasticity analysis

Revealing insect herbivory-induced phenolamide metabolism: from single genes to metabolic network plasticity analysis | Emerging Research in Plant Cell Biology | Scoop.it

The phenylpropanoid metabolic space comprises a network of interconnected metabolic branches that contribute to the biosynthesis of a large array of compounds with functions in plant development and stress adaptation. During biotic challenges, such as insect attack, a major rewiring of gene networks associated with phenylpropanoid metabolism is observed. This rapid reconfiguration of gene expression allows for the prioritized production of metabolites that help the plant solve ecological problems. Phenolamides are a group of phenolic-derivatives that originate from the diversion of hydroxycinnamoyl acids from the main phenylpropanoid pathway after N-acyltransferase-dependent conjugation to polyamines or aryl-monoamines. These structurally diverse metabolites are abundant in reproductive organs of many plants and have recently been shown to play roles as induced defenses in vegetative tissues. In the wild tobacco, Nicotiana attenuata in which the herbivory-induced regulation of these metabolites has been studied, rapid elevations of phenolamide levels that function as induced defenses result from a multi-hormonal signaling network that reshapes connected metabolic pathways. In this review, we summarize recent findings in the regulation of phenolamides obtained by mass spectrometry-based metabolomics and outline a conceptual framework for gene discovery in this pathway. We finally introduce a multifactorial approach useful in deciphering metabolic pathway reorganizations among different tissues in response to stress.

  
more...
No comment yet.
Rescooped by Jennifer Mach from MycorWeb Plant-Microbe Interactions
Scoop.it!

Botany: Special issue: The microbiota of plants

Botany: Special issue: The microbiota of plants | Emerging Research in Plant Cell Biology | Scoop.it

In this Special Issue, we have tried to capture the diversity of plant–microbe research that is on-going, and that might not normally be marketed under the banner of “plant microbiome research”. Nevertheless, it belongs under this banner and we highlight some of this research here, including a variety of plant “habitats” such as roots, leaves, and floral parts, as well as a variety of microbes, from bacteria and arbuscular mycorrhizal fungi to dark septate fungi. Of course, the field is broader than what we are able present in a single issue, but we hope that it inspires researchers of overlooked aspects of plant microbiota research to get in on the game, and contribute to a more complete picture of this complex “ecosystem”.


Via Stéphane Hacquard, Francis Martin
more...
No comment yet.