Suspects appearing to pledge allegiance to Isis arrested in cities of Eupen and La Calamine
The office of Belgium’s federal prosecutor says two underage people suspected of plotting what has been labelled a terror attack have been arrested
the suspects were arrested on 31 October after raids in the cities of Eupen and La Calamine
The prosecutor’s office said they were suspected of “attempted terrorist assassination and participation in a terrorist organisation.”
The two minors have been placed in a youth protection centre
the suspects had recorded a video of allegiance to Islamic State and were suspected of planning a stabbing attack against police officers
The arrests were made before Monday’s attack in Vienna, where a man who had previously tried to join Isis went on a rampage in the Austrian capital and fatally shot four people before being killed by police
Four years ago, coordinated attacks killed 32 people and injured hundreds more at Brussels’ Zaventem airport and on the city’s metro system. Belgian authorities have since thwarted several terror plots.
Belgium (Reuters) - A small town in Belgium that spent a century living outside the map of Europe's great power system celebrates the 200th anniversary of the quirky autonomy it secured in the wake of the Napoleonic wars.Neutral Moresnet was the name given to the sliver of land
that was home to a key deposit of the zinc ore calamine
It inspired tourists and anarchists - and utopian enthusiasts for the world language Esperanto - before succumbing to another round of the European bloodshed that gave it birth.Granted independence in 1816 to keep a peace between Dutch and Prussians following the defeat of its former French imperial masters at Waterloo
it was swept away 98 years later by World War One
in the small German-speaking region close to Aachen in Germany."This is a unique history
It has historical significance and that's a good reason to celebrate it," Kelmis mayor Louis Goebbels told Reuters at the start of a weekend of festivities for the bicentenary.These included parades by Napoleonic military reenactors and lectures on the prosperity and freedoms enjoyed by defenceless
tiny Moresnet amid a Europe held together ever more shakily by the balance of powers forged at the Congress of Vienna.Claimed by war-weary Prussians and Dutch
1816 divided the district of Moresnet between Berlin and Amsterdam with a narrow triangular strip containing the mine itself under shared control as Neutral Moresnet
it took over the Dutch interests there.Run by the Vieille Montagne company
which boomed by cladding the roofs of Paris and other cities with rain-proof zinc
territory soared from 256 in 1816 to nearly 5,000 by the start of World War One in 1914.PEACEFUL "ANARCHY"Mayor Goebbels relates how his forefathers came from Germany to the "neutral zone"
aware of a celebrity status that came from running its own state
offering a host of welfare services and sponsoring social clubs.For some there was also the draw that residents of what is known in French as La Calamine could avoid military service in Prussia or Belgium
drove a thriving liquor trade -- and much smuggling.Law was largely dispensed locally with a light touch.It is cited as a model by libertarians who liken it to self-governing communities of the Wild West: "Moresnet demonstrated the possibilities that statelessness holds out for peace
"A Century of Anarchy".The limits of Moresnet's independence
were obvious.When in 1886 the company doctor
hit on the idea of the territory's own postal service
the twin supervisory powers in Berlin and Brussels joined forces to stop him -- leaving just a few rare specimens.As the mine declined
Molly sought to make Neutral Moresnet a centre for Esperanto
an artificial "world language" intended to promote peace
Renaming the neutral zone "Amikejo" -- Esperanto for a place of friendship -- Molly even commissioned its own national anthem in 1908.But six years later
the breakdown of the "armed peace" that Europe had agreed at the Congress of Vienna a century earlier wiped Neutral Moresnet off the map
German troops swept it up and annexed it in their 1914 conquest of Belgium
it was handed wholesale to Belgium along with other German-speaking borderlands as part of Berlin's reparations.A century and another devastating European war later
though dozens of stone border markers still dot the fields and woods
people in Kelmis find it hard to imagine their forebears carving out a space between great-power frontiers bristling with guns."After two world wars
people here don't generally want to talk about the past," said Sylvie Fabeck
Her grandmother was the last person born in "free" Moresnet
"Are a chance to show what Neutral Moresnet was."It now lies in the 4-million-strong Meuse-Rhine Euroregion
an administrative area that embraces French-speaking Liege
German-speaking Eupen and Flemish Hasselt in Belgium
Charlemagne's 8th-century capital at Aachen in Germany and Maastricht
the Dutch home of the European Union treaty.Despite new checks on some of the EU's unpoliced borders since last year's migration crisis
the 11,000 multilingual people of Kelmis can now work easily in all three countries
As museum curator Fabeck puts it: "This is what is now Europe."Editing by Stephen Powell
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Volume 5 - 2014 | https://doi.org/10.3389/fpls.2014.00213
The metal hyperaccumulator Noccaea caerulescens is an established model to study the adaptation of plants to metalliferous soils
Various comparators have been used in these studies
The choice of suitable comparators is important and depends on the hypothesis to be tested and methods to be used
In high-throughput analyses such as microarray
caerulescens has been compared to non-tolerant
non-accumulator plants like Arabidopsis thaliana or Thlaspi arvense rather than to the related hypertolerant or hyperaccumulator plants
caerulescens populations with considerable variation in their capacity to accumulate and tolerate metals
Whole transcriptome sequencing (RNA-Seq) is revealing interesting variation in their gene expression profiles
Combining physiological characteristics of N
caerulescens accessions with their RNA-Seq has a great potential to provide detailed insight into the underlying molecular mechanisms
In this review we will critically consider comparative transcriptome analyses carried out to explore metal hyperaccumulation and hypertolerance of N
and demonstrate the potential of RNA-Seq analysis as a tool in evolutionary genomics
a number of plants with differences in hyperaccumulation and hypertolerance have been compared
This includes cross- and intra-species comparisons
and comparisons between accumulators and non-accumulators
The choice of comparators is important and depends on the hypothesis to be tested and methodology used
While deep sequencing techniques have the potential to greatly increase our understanding about the mechanisms of plant metal-related traits and their evolution during the adaptation to different environments
a careful consideration of appropriate comparators becomes increasingly important
A major challenge is to find the genes of interest among those differentially expressed between the plants
In this review we consider the choice of comparators in exploring metal hyperaccumulation and hypertolerance characteristics of N
and discuss the pros and cons of the approaches in relation to RNA-Seq analysis
caerulescens populations with contrasting metal tolerance or hyperaccumulation capacities is a superior tool to analyze the evolutionary genomics of plant adaptation strategies to metalliferous soils
The non-accumulator, non-tolerant Arabidopsis thaliana, a model plant from the Brassicaceae family, is considered as a good comparator to N. caerulescens because of considerable sequence similarity: 87-88% identity in intergenic transcribed spacer regions (Peer et al., 2003), and ca. 88.5% nucleotide identity within transcribed regions (Rigola et al., 2006)
thaliana are superior compared to any other plant
One of the first efforts to characterize the N. caerulescens transcriptome was made by Rigola et al. (2006), comparing ESTs (expressed sequence tags) of A. thaliana and N. caerulescens accession La Calamine, a Zn-tolerant Zn hyperaccumulator (Assunção et al., 2003c)
the complex comparison thus included Zn hyperaccumulator/non-accumulator pair
Zn tolerant/non-tolerant pair as well as different Zn concentrations
The assembled partial cDNA sequences (unigenes) represented only 13% of the root and shoot transcriptomes
Several unigenes showed similarity to genes for which a role in metal hyperaccumulation
tolerance or homeostasis was previously implicated
Three percent of the unigenes corresponded to A
thaliana orthologues not known to be expressed
An effort was made to estimate transcriptional activity of highly expressed genes from the frequency of their detection but
EST analysis provides limited information about transcript abundances
Zn-dependence of the expression would not be expected for these genes
which implied either species-specific differences in the mechanisms of metal hyperaccumulation or methodological differences
halleri at specific tissue- or even single cell level might help determining the specific mechanisms responsible for metal accumulation (e.g.
While cross-species microarray analyses have provided valuable information about N
caerulescens and its responses to environment compared to the related non-accumulators A
which may lead to a conclusion that there is a link between metal hyperaccumulation and a specific gene expression when in fact there is not
All microarray-based methods have limitations in terms of sensitivity and dynamic range
but a major challenge in cross-species comparisons is the sequence divergence of orthologous genes and thus the probe design
in estimating relative transcript abundances and to the lack of identification of novel transcripts
FIGURE 1. Predicted secondary structure of A. thaliana IRT1 metal transporter. The amino acid sequence was retrieved from TAIR10 database. The secondary structure of the protein was predicted using HMMTOP 2.0 (Tusnády and Simon, 1998, 2001). The diagram was generated with TEXtopo package (Beitz, 2000)
Amino acids known to be important for the function of IRT1 are labeled with stars and arrows
caerulescens amino acid sequences were derived from Illumina RNA-Seq analysis of three accessions: Lellingen
some of the highly expressed pathways probably contribute to these traits
The data are based on SOLiD RNA-Seq analysis of three biological replicates of three N
The read counts were normalized by the size of the libraries and the length of the genes
assuming an equal length for orthologous genes in A
and the most highly expressed genes (expression value > 1000) were subjected to a more detailed analysis
The genes were manually linked to metabolic pathways in KEGG (Kyoto Encyclopedia of Genes and Genomes)
and Ni concentrations among eighteen metallicolous
caerulescens populations in response to different cultivation conditions
These examples demonstrate highly contrasting metal tolerance and accumulation characteristics among N
and points to their potential for comparative RNA-Seq combined with association analyses
Co-segregation, genetic linkage mapping and quantitative trait loci (QTL) analyses make use of crosses between genotypes with contrasting phenotypes. Several crosses have been made between N. caerulescens accessions (Assunção et al., 2003a, 2006; Deniau et al., 2006; Richau and Schat, 2009)
expression QTL (eQTL) has not been applied so far to address metal hyperaccumulation or tolerance
Candidate gene identification can be further improved by applying RNA-Seq to recombinant inbred lines selected for particular tolerance or accumulation capacities or
Having populations with a wide range of metal hyperaccumulation and hypertolerance capacities
caerulescens shows a great potential to serve as an excellent model in plant evolutionary genomics
a significant leap forward is expected in the understanding of the metabolic adaptation of this plant to different metal environments
RNA-Seq still remains a screening method that provides candidate genes
a more detailed analysis being needed to prove the true significance of the findings
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest
This work was financially supported by the Academy of Finland (project No
We acknowledge CSC – IT Center for Science Ltd
for the allocation of computational resources
Specific hypomethylation of DNA is induced by heavy metals in white clover and industrial hemp
CrossRef Full Text
Assunção
A cosegregation analysis of zinc (Zn) accumulation and Zn tolerance in the Zn hyperaccumulator Thlaspi caerulescens
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Assunção
an attractive model species to study heavy metal hyperaccumulation in plants
CrossRef Full Text
Assunção
Differential metal tolerance and accumulation patterns among Thlaspi caerulescens populations originating from different soil types
CrossRef Full Text
Assunção
Construction of a genetic linkage map of Thlaspi caerulescens and quantitative trait loci analysis of zinc accumulation
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
High throughput sequencing reveals novel and abiotic stress-regulated microRNAs in the inflorescences of rice
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TEXtopo: shaded membrane protein topology plots in LATEX 2ε
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A novel CPx-ATPase from the cadmium hyperaccumulator Thlaspi caerulescens
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Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Identification of aluminum-responsive microRNAs in Medicago truncatula by genome-wide high-throughput sequencing
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Abiotic-stress induces demethylation and transcriptional activation of a gene encoding a glycerophosphodiesterase-like protein in tobacco plants
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Hyperaccumulation of cadmium and zinc in Thlaspi caerulescens and Arabidopsis halleri at the leaf cellular level
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Variation in HMA4 gene copy number and expression among Noccaea caerulescens populations presenting different levels of Cd tolerance and accumulation
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
QTL analysis of cadmium and zinc accumulation in the heavy metal hyperaccumulator Thlaspi caerulescens
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Fast computation and applications of genome mappability
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
A comprehensive evaluation of normalization methods for Illumina high-throughput RNA sequencing data analysis
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
A novel iron-regulated metal transporter from plants identified by functional expression in yeast
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Escarré
Metal concentration and metal mass of metallicolous
non metallicolous and serpentine Noccaea caerulescens populations
CrossRef Full Text
Constitutively elevated salicylic acid signals glutathione-mediated nickel tolerance in Thlaspi nickel hyperaccumulators
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Metal-binding thermodynamics of the histidine-rich sequence from the metal-transport protein IRT1 of Arabidopsis thaliana
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Gene expression differences between Noccaea caerulescens ecotypes help to identify candidate genes for metal phytoremediation
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
A comparison of the Thlaspi caerulescens and Thlaspi arvense shoot transcriptomes
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Evolution of metal hyperaccumulation required cis-regulatory changes and triplication of HMA4
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Iron-induced turnover of the Arabidopsis Iron-Regulated Transporter1 metal transporter requires lysine residues
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Taxonomy and systematics are key to biological information: Arabidopsis
Noccaea and Schrenkiella (Brassicaceae) as examples
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
The IRT1 protein from Arabidopsis thaliana is a metal transporter with a broad substrate range
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Tandem quadruplication of HMA4 in the zinc (Zn) and cadmium (Cd) hyperaccumulator Noccaea caerulescens
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Cadmium accumulation in populations of Thlaspi caerulescens and Thlaspi goesingense
CrossRef Full Text
Marquès
Heavy metal specificity of cellular tolerance in two hyperaccumulating plants
Arabidopsis halleri and Thlaspi caerulescens
CrossRef Full Text
Heavy metal tolerance and accumulation in metallicolous and non-metallicolous populations of Thlaspi caerulescens from continental Europe
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In vivo speciation of zinc in Noccaea caerulescens in response to nitrogen form and zinc exposure
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Transgenerational inheritance of modified DNA methylation patterns and enhanced tolerance induced by heavy metal stress in rice (Oryza sativa L.)
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Identifying model metal hyperaccumulating plants: germplasm analysis of 20 Brassicaceae accessions from a wide geographical area
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The extracellular loop of IRT1 ZIP protein - the chosen one for zinc
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Comprehensive evaluation of differential expression analysis methods for RNA-seq data
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Heavy metal hyperaccumulating plants: how and why do they do it
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Distribution and metal-accumulating behavior of Thlaspi caerulescens and associated metallophytes in France
CrossRef Full Text
Intraspecific variation of nickeland zinc accumulation and tolerance in the hyperaccumulatoro Thlaspi caerulescens
CrossRef Full Text
The heavy metal hyperaccumulator Thlaspi caerulescens expresses many species-specific genes
as identified by comparative expressed sequence tag analysis
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
The potential of Thlaspi caerulescens for phytoremediation of contaminated soils
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Altered selectivity in an Arabidopsis metal transporter
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Comparative studies of gene expression and the evolution of gene regulation
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Natural variation in cadmium tolerance and its relationship to metal hyperaccumulation for sevel populations of Thlaspi caerulescens from Western Europe
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Phytoextraction of cadmium with Thlaspi caerulescens
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Zinc-dependent global transcriptional control
and higher gene copy number for genes in metal homeostasis of the hyperaccumulator Arabidopsis halleri
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Distinctive effects of cadmium on glucosinolate profiles in Cd hyperaccumulator Thlaspi praecox and non-hyperaccumulator Thlaspi arvense
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Tusnády
Principles governing amino acid composition of integral membrane proteins: applications to topology prediction
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Tusnády
The HMMTOP transmembrane topology prediction server
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Expression differences for genes involved in lignin
glutathione and sulfate metabolism in response to cadmium in Arabidopsis thaliana and the related Zn/Cd-hyperaccumulator Thlaspi caerulescens
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Large expression differences in genes for iron and zinc homeostasis
and lignin biosynthesis distinguish roots of Arabidopsis thaliana and the related metal hyperaccumulator Thlaspi caerulescens
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Vázquez
Localization of zinc and cadmium in Thlaspi caerulescens (Brassicaceae)
a metallophyte that can hyperaccumulate both metals
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Vogel-Mikuš
and Pb accumulation and arbuscular mycorrhizal colonization of pennycress Thlaspi praecox Wulf
(Brassicaceae) from the vicinity of a lead mine and smelter in Slovenia
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Association between up-regulation of stress-responsive genes and hypomethylation of genomic DNA in tobacco plants
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Comparative microarray analysis of Arabidopsis thaliana and Arabidopsis halleri roots identifies nicotianamine synthase
a ZIP transporter and other genes as potential metal hyperaccumulation factors
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Organic acids are not specifically involved in the nitrate-enhanced Zn hyperaccumulation mechanism in Noccaea caerulescens
CrossRef Full Text
Variation in root-to-shoot translocation of cadmium and zinc among different accessions of the hyperaccumulators Thlaspi caerulescens and Thlaspi praecox
Pubmed Abstract | Pubmed Full Text | CrossRef Full Text
Citation: Halimaa P, Blande D, Aarts MGM, Tuomainen M, Tervahauta A and Kärenlampi S (2014) Comparative transcriptome analysis of the metal hyperaccumulator Noccaea caerulescens. Front. Plant Sci. 5:213. doi: 10.3389/fpls.2014.00213
Copyright © 2014 Halimaa, Blande, Aarts, Tuomainen, Tervahauta and Kärenlampi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)
distribution or reproduction in other forums is permitted
provided the original author(s) or licensor are credited and that the original publication in this journal is cited
in accordance with accepted academic practice
distribution or reproduction is permitted which does not comply with these terms
*Correspondence: Pauliina Halimaa, Department of Biology, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland e-mail:cGF1bGlpbmEuaGFsaW1hYUB1ZWYuZmk=
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.
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proving their sanctioned blessings from the old school Kings
While some of those bands were pushing boundaries and innovating
Nasty is proud just to provide one of the heaviest and crushing albums with Menace’s disdain for the current climate of chaos
For any fan feeling penned up and frustrated
whether due to isolation or political melee or unemployment or loss and grief
The pounding rhythms and riffs beg for release and destruction
(video below) sets the tone in two and half minutes
And lays the foundation for the following down-tuned thunder
Any audience who somehow resists the urge to swing fists and swing kicks
will still be bobbing the head in the groove of the mid-paced chugging’s and low-end splendor
OFFICAL “Menace” Video: https://www.youtube.com/watch?v=EoGoQvFtwSM
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Milia appear out of nowhere: a slew of tiny and painless — albeit pesky — white bumps
but you figure you can try to pop them anyway because textured skin isn't what you're going for
It's a totally unexplainable popping fail
While milia do indeed look like whiteheads
that's where most of the comparisons end
"Milia is where the skin grows completely over a pore and the skin debris is trapped beneath the surface," he says
it is difficult to remove and often requires a tool to open the skin's surface and pop out the hard white core."
milia can develop without rhyme or reason and cannot be extracted the way typical blemishes can
Read on for the deep dive on milia and how you can treat those little bumps
these tiny white bumps can happen to just about anyone regardless of age or skin type
but they are more prevalent in those with chronic sun damage
[and can] be seen in all age groups from babies to adults," she says
Dr. Marchbein says milia can pop up without rhyme or reason, but she also notes that they're more commonly found in conjunction with certain skin conditions such as rosacea and dandruff
or when skin-care and makeup products clog pores and cause buildup
milia can also occur when keratin gets trapped under the surface of the skin due to skin trauma like burns
or after the use of certain topical medications
"Retinoids and exfoliants can help with oil production and clogging and are great for preventing milia." Unfortunately
because the cause of milia isn't necessarily as clear as for an acne breakout
using these products doesn't guarantee you won't get milia in the future
there is no true way to permanently prevent them from forming," adds Dr
there's a whole host of ways to kick 'em to the curb
"These topicals help minimize their occurrence
you can try to use a comedone extractor after first softening the bump with a warm-water compress
the best plan of action for milia removal is to visit a dermatologist
You could also fail to remove the lesion and even develop an infection."
A dermatologist can de-roof the milia with a sterile needle or scalpel — or with a laser treatment
is done with an electrically heated needle
Check out Hailey Bieber's 10 beauty commandments:
Volume 11 - 2020 | https://doi.org/10.3389/fpls.2020.582577
This article is part of the Research TopicVernalization and Flowering Time: Celebrating 20 Years of FLCView all 15 articles
The appropriate timing of flowering is crucial for plant reproductive success
Studies of the molecular mechanism of flower induction in the model plant Arabidopsis thaliana showed long days and vernalization as major environmental promotive factors
Noccaea caerulescens has an obligate vernalization requirement that has not been studied at the molecular genetics level
we characterize the vernalization requirement and response of four geographically diverse biennial/perennial N
Differences in vernalization responsiveness among accessions suggest that natural variation for this trait exists within N
Mutants which fully abolish the vernalization requirement were identified and were shown to contain mutations in the FLOWERING LOCUS C (NcFLC) and SHORT VEGETATIVE PHASE (NcSVP) genes
the non-vernalization requiring flc-1 mutant reverts from flowering to vegetative growth
which is accompanied with a reduced expression of LFY and AP1
This suggested there is “crosstalk” between vernalization and ambient temperature
which might be a strategy to cope with fluctuations in temperature or adopt a more perennial flowering attitude and thus facilitate a flexible evolutionary response to the changing environment across the species range
but the genetic basis and molecular mechanisms of flowering time regulation has not been studied yet in this species
A better understanding of the genetic control of flowering time in N. caerulescens will help us to understand its morphological and phenotypic behavior as an adaptation to climate conditions. Day lengths of 8 and 12 h did not influence the flowering time when a 4°C cold treatment was applied to induce flowering, indicating that only temperature seems important to induce flowering in N. caerulescens (Guimarães et al., 2013)
In addition to the natural occurring variation
the identification of early flowering time mutations will also be important for uncovering the key genes involved in the flowering time regulation pathway
The present study investigates the variation of the vernalization requirement and response in four representative N
caerulescens accessions from diverse environments
We confirm the essential roles of FLC and SVP by the identification of mutations in these genes in early non-vernalization requiring plants obtained by forward screening of an EMS-mutagenesis-induced M2 population
a flowering time regulation model in the biennial/perennial species N
including the effect of high ambient temperatures
the seeds were imbibed at 4°C for 4 days before sowing in pots with a mix of fertilized peat and sand under standard greenhouse conditions (16 h light/8 h dark cycle) set at 23°C and 65% relative humidity
the plants were vernalized in a cold growth room (at 4°C
after 60 days of vegetative growth in the standard greenhouse conditions
and subsequently transferred back to the same greenhouse
To examine the temperature effect on flowering time
seeds were sown in a growth chamber (16 h light/8 h dark) set at 20°C or 30°C
The rosette leaves and inflorescences distal from open flowers were collected for RNA extraction when the first flower had opened
The inflorescence samples may have contained a few small bracts
The effect of a cold period on inflorescence number was evaluated by counting the number of inflorescences 30 days after the transfer back to the warm greenhouse
The subsequent inflorescences on the side shoots were not included
RNA was extracted following a Trizol protocol (Oñate-Sánchez and Vicente-Carbajosa, 2008) and treated with DNA-free DNase (Promega)
RNA quality and quantity were determined using agarose gel electrophoresis and a NanoDrop ND1000 spectrophotometer (NanoDrop Technologies
cDNA was synthesized from 1 μg of total RNA using a cDNA reverse transcription kit (iScriptTMcDNA Synthesis Kit) following the protocol recommended by the manufacturer
Three to five biological replicates for each treatment or accession were used for the analysis
the appropriate primer efficiency for each gene was verified
and Arabis alpina and the splice variants of NcFLC and NcSVP were aligned using the Bioedit program
The three mutants that carry flc mutant alleles were inter-crossed and crossed with putative svp mutants and WT
were also crossed to the flc-1 and svp-1 mutants and each other
The F1 plants were grown under control conditions
Flowering time of the F1 plants was determined as the number of days after sowing when the first flower opened
The flowering time of the F2 plants derived from the cross between the early flowering mutants and the SF WT was determined in the same way and the same conditions
only a few inflorescences developed after this cold treatment
the time to flowering was increased in LE and LC
In these accessions some parts of the inflorescences that had bolted did not start flowering at all
indicating that not in all meristems the transition to flowering was completed
After 10 weeks of cold treatment the number of days to bolting and to flowering was reduced to on average
indicating that the vernalization requirement was fully satisfied
LE flowered the earliest amongst all accessions
with all siliques being well-developed at 30 days after 10 and 12 weeks of cold
while the other three accessions were still flowering
Variation in vernalization response and NcFLC expression of selected N
(A) The transition to flowering as determined by the time to bolting (first flower bud visible) for non-vernalized (NV) plants and for plants vernalized for the indicated number of weeks (W)
(B) The time to flowering (first petal visible); and (C) the number of inflorescences per plant in the same treatments as (A)
(D) The relative expression of NcFLC in rosette leaves upon vernalization for the indicated number of weeks
relative to the expression of NcFLC in SF after 12 weeks of vernalization (=1)
The expression of NcTubulin is used to normalize cDNA concentrations
Values are the mean of three to five plants
NV-1: 2-month-old non-vernalized plants; NV-2: 5-month-old non-vernalized plants
the NcFLC transcript threshold to repress flowering seems much higher than in LE
with GA only requiring 4 weeks of vernalization to induce flowering at a higher NcFLC expression level than LE
One reason why the four accessions required different weeks of cold for the full acceleration of flowering could be that NcFLC expression recovers differently between accessions after the transfer to warmer conditions. Therefore, we also determined the maintenance of NcFLC gene expression in the four accessions at 10 and 30 days after the vernalization treatment (Figure 2)
the relative NcFLC expression indeed increased 10 days after returning to the warm greenhouse in LC
NcFLC transcript levels stayed constantly low
NcFLC expression increased again after 30 days in the warm greenhouse
but the increase was less prominent in GA and LE compared to SF and LC
the NcFLC expression remained more repressed the longer the cold period lasted
NcFLC transcript levels are relatively more stably repressed than in LE and LC
when the cold treatment lasted up to 10 weeks
at which time flowering is induced in all accessions
This suggests that the recovery of NcFLC transcript levels immediately after the transfer to the warm greenhouse
correlates with the absence of flowering after a short period of vernalization
Variation in maintaining repression of NcFLC expression upon vernalization
caerulescens rosette leaves of accessions Ganges (GA)
and La Calamine (LC) of plants either non-vernalized (NV-1; 6 months after sowing) or vernalized for 4
or 12 weeks (W) at 4°C after 2 months of growth at 23°C
and subsequently returned to the warm greenhouse
and 30 days (Days) following the vernalization treatment
Expression is expressed relative to the expression of NcFLC in SF after 12 weeks of vernalization in rosette leaves collected directly after vernalization (=1)
Each value represents the mean of three to five plants
Identification and analysis of early flowering N
Felix de Pallières (SF) wild type (WT) growing without vernalization
(B) Relative expression of NcFLC in rosette leaves of early flowering mutants and WT plants
(C) Relative expression of NcSVP in rosette leaves of early flowering mutants and WT plants
(D) Days to bolting of self-fertilized and F1 progeny of the early flowering mutants and inter-mutant or mutant-WT crosses growing under non-vernalizing conditions
GA-A7 and GA-A2 are the early flowering mutants in Ganges (GA) background
Rosette leaves for expression analysis were collected when the first flower had opened
Expression levels were determined relative to the expression of NcTubulin (=1)
Each value represents at least three plants ± SE
Asterisks indicate significant differences from WT
all F1 plants derived from the back-cross with WT (T10-42
and T81-27) and the F1 hybrids between T81-27 and the three mutants of the first complementation group did not flower in these conditions indicating that T81-27 carries a mutation at a second locus
Analysis of the BC1S1 progeny of the mutant × WT crosses under non-vernalization conditions revealed that all the segregation ratios agreed with a Mendelian 3: 1 ratio of non-flowering: early flowering plants (data not shown)
which shows that this mutant is affected in another gene
caerulescens FLC and SVP DNA sequences in WT and the flc and svp mutants
(A) Schematic representation of the Arabidopsis thaliana FLC genomic DNA (gDNA) sequence (AtFLC) compared to the NcFLC genomic DNA sequence in N
Numbers indicate total DNA sequence length in base pairs
Intron DNA sequences are indicated with a horizontal black line
5′ and 3′ untranslated regions (UTR) are indicated with red boxes
Protein coding exons are indicated with green boxes
G to A single base pair mutations are found in all mutants
The mutations in flc-1 and flc-2 are identical
The mutation in these mutants locates at the 3′ splice junction of exon 3
while the mutation in flc-3 locates at the 5′ splice junction of exon 3
(B) Schematic representation of NcFLC coding sequences (CDS) of the N
The G to A mutation in flc-1/flc-2 causes an in-frame substitution of exon 3 sequence
while the mutation in flc-3 leads to a 9 bp deletion at the start of exon 3
the alternative exon 3 in the flc-1/flc-2 CDS is indicated with a horizontal black line
a G to A mutation was found at the 3’ splice junction of exon 4
The mutation in svp-1 causes an in-frame deletion of part of exon 4
while the mutation in svp-2 leads to a single amino acid change of Leucine to Phenylalanine in exon 1
The numbers at the end of each line indicate the total number of nucleotides
As this is likely to alter the SVP function in this mutant
this could not be confirmed by allelism tests because of the complete sterility of this mutant
So far, the plants used in this study had been selected and grown during winter in a heated greenhouse. When growing the plants in late spring or summer, we noticed that these plants did not flower properly (Supplementary Figure S3)
During these periods the day temperature often exceeded 30°C
This prompted us to examine whether the higher ambient temperatures affect flowering in N
WT and flc-1 mutant plants were grown in climate-controlled growth chamber under long day conditions (16/8 h day/night)
with the day temperature set at either 20°C or 30°C and the night temperature at 18°C
The flowering time was determined as the number of days between sowing and bolting of each plant
This indicates that the reproductive fitness of the plants is fine at an ambient day temperature of 20°C
but strongly reduced at the higher temperature of 30°C
The phenotype of WT and flc-1 mutant plants at two different day temperatures
(A) Flowering plants of WT and the flc-1 mutant grown for 2 months at either 20 or 30°C
(B) The primary inflorescence of the flc-1 mutant grown at 20°C
(C) The primary inflorescence and (D) a secondary inflorescence of the flc-1 mutant grown at 30°C
(E) The inflorescence top of the flc-1 mutant at 20°C and at (F) 30°C
(G) The leaves on a primary inflorescence of the flc-1 mutant when grown at 20°C (left) and 30°C (right)
To further investigate the effects of the day temperature differences on flowering of N. caerulescens, the expression of flowering genes was determined in rosette leaves and the inflorescence heads (the top parts of an inflorescence, containing the flower buds and no open flowers) of flc-1 and WT plants growing at 20°C and 30°C day temperatures (Figure 6)
The analysis included the floral repressor genes NcFLC and NcSVP
the expression of floral integrators FLOWERING LOCUS T (NcFT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS (NcSOC1) as well as the floral organ identify genes LEAFY (NcLFY) and APETALA1 (NcAP1)
Higher NcFLC transcript levels were detected in the rosette leaves of WT at 20°C than at 30°C indicating that the temperature influences the expression of NcFLC
NcSVP expression was up-regulated in rosette leaves at 30°C
with slightly lower expression observed in the flc-1 mutant
but more up-regulated in leaves of the flc-1 mutant than in WT under both temperatures
the expression levels of the floral organ identify genes NcLFY and NcAP1 were considerably down-regulated in the inflorescence heads at 30°C compared to 20°C
Especially NcAP1 expression was 14 times higher in the flc-1 mutant at 20°C than at 30°C
caerulescens genes in different organs and temperatures
NcLFY and NcAP1 in rosette leaves (leaf) and flowering heads (FH) of St
Felix de Pallières wild-type (WT) and flc-1 mutant plants grown at 20°C (blue bars) or 30°C (red bars)
Expression levels are expressed relative to the expression of NcFT in WT (=1)
Values indicate the average of at least three plants ± SE
Asterisks indicate significant differences between 20°C and 30°C
a faster vernalization response is predicted to confer a selective advantage to plants that flower earlier thus to avoid early summer droughts and high temperatures that results in poor seed set
LE and LC originate from Luxembourg and Belgium
and are biennial or facultative perennial accessions
that will have to deal with more severe winters and cooler summers compared to the French accessions
This implies that these accessions should have more opportunities to satisfy the longer vernalization period they require and allowing them to flower later than the accessions from southern France when compared under the same conditions
NcSVP or any of the NcMAF genes and did not show any mutations in the cDNA sequences of these genes (data not shown)
which indicates that there is at least a third locus in N
caerulescens required for suppression of flowering in non-vernalizing conditions
Since none of the above-mentioned candidate genes are affected
map-based cloning and genome sequencing will be needed to identify the causal mutation
The observation that single mutants of all three genes result in early flowering indicates that they operate in mutual dependency
Although N.caerulescens is typically a vernalization-obligate species
investigating the photoperiod response would enhance the understanding of NcSVP functionality
as in NcFLC the sequences of the exon 1 duplications are identical
Since both biennial and perennial plants were found in the field for the LE and LC accessions
the perpetual flowering habit might be part of the life style in some N
It appears to be rarer for the SF and GA accessions
which may very well be related to the summer conditions at the locations where these accessions are found
These are much warmer and especially drier than those of the more northern accessions
and therefore much less likely to support proper perennial growth of N
The partially stable expression of NcFLC seems to be intermediate between A
corresponding to the somewhat intermediate life style
will be interesting to fully understand this complex trait
Such reversion might be an advantage in dry and hot
which would not be favorable for reproduction
The identification of N. caerulescens genes that control flowering allows us to compare the molecular pathways controlling seasonal flowering in N. caerulescens with those in A. thaliana. Based on the transcriptional analysis of key genes in the vernalization pathway, in the non-vernalization requiring mutants, we propose a flowering time regulation model for N. caerulescens (Figure 7)
caerulescens is further affected by down-regulation of the floral identity genes NcLFY and NcAP1 under high temperatures
as we expect to happen late in spring or summer
This occurs despite the upregulated expression of floral integrators such as NcFT and NcSOC1
The temperature sensitivity of the regulating genes LFY and AP1 will be an interesting topic for further study in other biennial or perennial species
Model of the flowering time regulation pathway in N
the vernalization pathway resembles that of A
but no longer able to induce the downstream floral identity genes NcLFY and NcAP1
which delays and disturbs floral initiation at this temperature
which functions parallel to NcFLC and NcSVP
may suppress the expression of NcLFY and NcAP1 at 30°C
Bar-ended lines indicate repression of expression
Solid lines indicate confirmed expression effects
while dotted lines indicate interactions still unconfirmed
The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/ Supplementary Material
and MA designed the experiments and wrote the manuscript
All authors contributed to the article and approved the submitted version
This research was financially supported by the China Scholarship Council (CSC) and the Consortium for Improving Plant Yield (CIPY)
United Kingdom) for providing the seeds of early flowering GA mutants and Corrie Hanhart (Laboratory of Genetics
Wageningen University) for her help with sowing M1 seeds and harvesting seeds from the M2 population
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpls.2020.582577/full#supplementary-material
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Copyright © 2020 Wang, Severing, Koornneef and Aarts. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)
provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited
*Correspondence: Yanli Wang, d3lsZnJpZW5kQDE2My5jb20=; Mark G. M. Aarts, bWFyay5hYXJ0c0B3dXIubmw=
†Present address: Edouard I. Severing, Max-Planck-Institute for Plant Breeding Research, Cologne, Germany
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