RESUMO
Genome interpretation (GI) encompasses the computational attempts to model the relationship between genotype and phenotype with the goal of understanding how the first leads to the second. While traditional approaches have focused on sub-problems such as predicting the effect of single nucleotide variants or finding genetic associations, recent advances in neural networks (NNs) have made it possible to develop end-to-end GI models that take genomic data as input and predict phenotypes as output. However, technical and modeling issues still need to be fixed for these models to be effective, including the widespread underdetermination of genomic datasets, making them unsuitable for training large, overfitting-prone, NNs. Here we propose novel GI models to address this issue, exploring the use of two types of transfer learning approaches and proposing a novel Biologically Meaningful Sparse NN layer specifically designed for end-to-end GI. Our models predict the leaf and seed ionome in A.thaliana, obtaining comparable results to our previous over-parameterized model while reducing the number of parameters by 8.8 folds. We also investigate how the effect of population stratification influences the evaluation of the performances, highlighting how it leads to (1) an instance of the Simpson's Paradox, and (2) model generalization limitations.
Assuntos
Arabidopsis , Genoma de Planta , Folhas de Planta , Sementes , Arabidopsis/genética , Folhas de Planta/genética , Folhas de Planta/metabolismo , Sementes/genética , Sementes/metabolismo , Redes Neurais de Computação , Genômica/métodos , Fenótipo , Modelos Genéticos , GenótipoRESUMO
Covering: up to 2023Specialized metabolite (SM) modifications and/or decorations, corresponding to the addition or removal of functional groups (e.g. hydroxyl, methyl, glycosyl or acyl group) to SM structures, contribute to the huge diversity of structures, activities and functions of seed and plant SMs. This review summarizes available knowledge (up to 2023) on SM modifications in Brassicaceae and their contribution to SM plasticity. We give a comprehensive overview on enzymes involved in the addition or removal of these functional groups. Brassicaceae, including model (Arabidopsis thaliana) and crop (Brassica napus, Camelina sativa) plant species, present a large diversity of plant and seed SMs, which makes them valuable models to study SM modifications. In this review, particular attention is given to the environmental plasticity of SM and relative modification and/or decoration enzymes. Furthermore, a spotlight is given to SMs and related modification enzymes in seeds of Brassicaceae species. Seeds constitute a large reservoir of beneficial SMs and are one of the most important dietary sources, providing more than half of the world's intake of dietary proteins, oil and starch. The seed tissue- and stage-specific expressions of A. thaliana genes involved in SM modification are presented and discussed in the context of available literature. Given the major role in plant phytochemistry, biology and ecology, SM modifications constitute a subject of study contributing to the research and development in agroecology, pharmaceutical, cosmetics and food industrial sectors.
Assuntos
Brassicaceae , Sementes , Sementes/metabolismo , Sementes/química , Brassicaceae/metabolismo , Brassicaceae/química , Estrutura Molecular , Proteínas de Plantas/metabolismoRESUMO
Cadmium (Cd) accumulation is highly variable among Arabidopsis halleri populations. To identify cell wall (CW) components that contribute to the contrasting Cd accumulation between PL22-H (Cd-hyperaccumulator) and I16-E (Cd-excluder), Cd absorption capacity of CW polysaccharides, CW mono- and poly- saccharides contents and CW glycan profiles were compared between these two populations. PL22-H pectin contained 3-fold higher Cd concentration than I16-E pectin in roots, and (1â4)-ß-galactan pectic epitope showed the biggest difference between PL22-H and I16-E. CW-related differentially expressed genes (DEGs) between PL22-H and I16-E were identified and corresponding A. thaliana mutants were phenotyped for Cd tolerance and accumulation. A higher Cd translocation was observed in GALACTAN SYNTHASE1 A. thaliana knockout and overexpressor mutants, which both showed a lengthening of the RG-I sidechains after Cd treatment, contrary to the wild-type. Overall, our results support an indirect role for (1â4)-ß-galactan in Cd translocation, possibly by a joint effect of regulating the length of RG-I sidechains, the pectin structure and interactions between polysaccharides in the CW. The characterization of other CW-related DEGs between I16-E and PL22-H selected allowed to identify a possible role in Zn translocation for BIIDXI and LEUNIG-HOMOLOG genes, which are both involved in pectin modification.
Assuntos
Arabidopsis , Arabidopsis/genética , Cádmio , Pectinas/química , Galactanos , Polissacarídeos , Parede Celular , Raízes de PlantasRESUMO
Elucidating the mechanisms that control seed development, metabolism, and physiology is a fundamental issue in biology. Michel Caboche had long been a catalyst for seed biology research in France up until his untimely passing away last year. To honour his memory, we have updated a review written under his coordination in 2010 entitled "Arabidopsis seed secrets unravelled after a decade of genetic and omics-driven research". This review encompassed different molecular aspects of seed development, reserve accumulation, dormancy and germination, that are studied in the lab created by M. Caboche. We have extended the scope of this review to highlight original experimental approaches implemented in the field over the past decade such as omics approaches aimed at investigating the control of gene expression, protein modifications, primary and specialized metabolites at the tissue or even cellular level, as well as seed biodiversity and the impact of the environment on seed quality.
L'élucidation des mécanismes qui contrôlent le développement, le métabolisme et la physiologie des graines est une question fondamentale en biologie. Michel Caboche a longtemps été un catalyseur de la recherche en biologie des graines en France jusqu'à son décès prématuré l'année dernière. Pour honorer sa mémoire, nous avons mis à jour une revue écrite sous sa coordination en 2010 intitulée « Arabidopsis seed secrets unravelled after a decade of genetic and omics-driven research ¼. Cette revue englobait différents aspects moléculaires du développement des graines, de l'accumulation des réserves, de la dormance et de la germination, qui sont étudiés dans le laboratoire créé par M. Caboche. Nous avons étendu la portée de cette revue pour mettre en évidence des approches expérimentales originales mises en Åuvre dans le domaine au cours de la dernière décennie, telles que les approches omiques visant à étudier le contrôle de l'expression des gènes, les modifications des protéines, les métabolites primaires et spécialisés au niveau des tissus ou même des cellules, tout en tenant compte de la biodiversité des graines et de l'impact de l'environnement sur leur qualité.
Assuntos
Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Sementes/genética , Biologia Molecular , Biologia , França , Germinação/genética , Dormência de Plantas/genética , Regulação da Expressão Gênica de PlantasRESUMO
The identification of transcription factor (TF) target genes is central in biology. A popular approach is based on the location by pattern matching of potential cis-regulatory elements (CREs). During the last few years, tools integrating next-generation sequencing data have been developed to improve the performance of pattern matching. However, such tools have not yet been comprehensively evaluated in plants. Hence, we developed a new streamlined method aiming at predicting CREs and target genes of plant TFs in specific organs or conditions. Our approach implements a supervised machine learning strategy, which allows decision rule models to be learnt using TF ChIP-chip/seq experimental data. Different layers of genomic features were integrated in predictive models: the position on the gene, the DNA sequence conservation, the chromatin state and various CRE footprints. Among the tested features, the chromatin features were crucial for improving the accuracy of the method. Furthermore, we evaluated the transferability of predictive models across TFs, organs and species. Finally, we validated our method by correctly inferring the target genes of key TFs controlling metabolite biosynthesis at the organ level in Arabidopsis. We developed a tool-Wimtrap-to reproduce our approach in plant species and conditions/organs for which ChIP-chip/seq data are available. Wimtrap is a user-friendly R package that supports an R Shiny web interface and is provided with pre-built models that can be used to quickly get predictions of CREs and TF gene targets in different organs or conditions in Arabidopsis thaliana, Solanum lycopersicum, Oryza sativa and Zea mays.
Assuntos
Arabidopsis , Fatores de Transcrição , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Ligação Proteica/genética , Genômica , Plantas/metabolismo , Cromatina/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Sítios de Ligação/genéticaRESUMO
In many cases, the unprecedented availability of data provided by high-throughput sequencing has shifted the bottleneck from a data availability issue to a data interpretation issue, thus delaying the promised breakthroughs in genetics and precision medicine, for what concerns Human genetics, and phenotype prediction to improve plant adaptation to climate change and resistance to bioagressors, for what concerns plant sciences. In this paper, we propose a novel Genome Interpretation paradigm, which aims at directly modeling the genotype-to-phenotype relationship, and we focus on A. thaliana since it is the best studied model organism in plant genetics. Our model, called Galiana, is the first end-to-end Neural Network (NN) approach following the genomes in/phenotypes out paradigm and it is trained to predict 288 real-valued Arabidopsis thaliana phenotypes from Whole Genome sequencing data. We show that 75 of these phenotypes are predicted with a Pearson correlation ≥0.4, and are mostly related to flowering traits. We show that our end-to-end NN approach achieves better performances and larger phenotype coverage than models predicting single phenotypes from the GWAS-derived known associated genes. Galiana is also fully interpretable, thanks to the Saliency Maps gradient-based approaches. We followed this interpretation approach to identify 36 novel genes that are likely to be associated with flowering traits, finding evidence for 6 of them in the existing literature.
Assuntos
Arabidopsis , Arabidopsis/genética , Genoma , Estudo de Associação Genômica Ampla , Genótipo , Redes Neurais de Computação , Fenótipo , Sequenciamento Completo do GenomaRESUMO
Lytic Polysaccharide Monooxygenases (LPMOs) are powerful redox enzymes able to oxidatively cleave recalcitrant polysaccharides. Widely conserved across biological kingdoms, LPMOs of the AA9 family are deployed by phytopathogens to deconstruct cellulose polymers. In response, plants have evolved sophisticated mechanisms to sense cell wall damage and thus self-triggering Damage Triggered Immunity responses. Here, we show that Arabidopsis plants exposed to LPMO products triggered the innate immunity ultimately leading to increased resistance to the necrotrophic fungus Botrytis cinerea. We demonstrated that plants undergo a deep transcriptional reprogramming upon elicitation with AA9 derived cellulose- or cello-oligosaccharides (AA9_COS). To decipher the specific effects of native and oxidized LPMO-generated AA9_COS, a pairwise comparison with cellobiose, the smallest non-oxidized unit constituting cellulose, is presented. Moreover, we identified two leucine-rich repeat receptor-like kinases, namely STRESS INDUCED FACTOR 2 and 4, playing a crucial role in signaling the AA9_COS-dependent responses such as camalexin production. Furthermore, increased levels of ethylene, jasmonic and salicylic acid hormones, along with deposition of callose in the cell wall was observed. Collectively, our data reveal that LPMOs might play a crucial role in plant-pathogen interactions.
Assuntos
Arabidopsis/imunologia , Botrytis/imunologia , Celulose/metabolismo , Oxigenases de Função Mista/metabolismo , Oligossacarídeos/metabolismo , Doenças das Plantas/imunologia , Arabidopsis/metabolismo , Arabidopsis/microbiologia , Resistência à Doença , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Oxigenases de Função Mista/fisiologia , Oligossacarídeos/fisiologia , Doenças das Plantas/microbiologia , Sordariales/metabolismoRESUMO
Metallophytes constitute powerful models for the study of metal homeostasis, adaptation to extreme environments and the evolution of naturally selected traits. Arabidopsis halleri is a pseudometallophyte which shows constitutive zinc/cadmium (Zn/Cd) tolerance and Zn hyperaccumulation but high intraspecific variability in Cd accumulation. To examine the molecular basis of the variation in metal tolerance and accumulation, ionome, transcriptome and cell wall glycan array profiles were compared in two genetically close A. halleri populations from metalliferous and nonmetalliferous sites in Northern Italy. The metallicolous population displayed increased tolerance to and reduced hyperaccumulation of Zn, and limited accumulation of Cd, as well as altered metal homeostasis, compared to the nonmetallicolous population. This correlated well with the differential expression of transporter genes involved in trace metal entry and in Cd/Zn vacuolar sequestration in roots. Many cell wall-related genes were also more highly expressed in roots of the metallicolous population. Glycan array and histological staining analyses demonstrated that there were major differences between the two populations in terms of the accumulation of specific root pectin and hemicellulose epitopes. Our results support the idea that both specific cell wall components and regulation of transporter genes play a role in limiting accumulation of metals in A. halleri at contaminated sites.
Assuntos
Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Cádmio/metabolismo , Parede Celular/metabolismo , Regulação da Expressão Gênica de Plantas , Homeostase , ItáliaRESUMO
Pseudometallophytes are commonly used to study the evolution of metal tolerance and accumulation traits in plants. Within the Arabidopsis genus, the adaptation of Arabidopsis halleri to metalliferous soils has been widely studied, which is not the case for the closely related species Arabidopsis arenosa. We performed an in-depth physiological comparison between the A. halleri and A. arenosa populations from the same polluted site, together with the geographically close non-metallicolous (NM) populations of both species. The ionomes, growth, photosynthetic parameters and pigment content were characterized in the plants that were growing on their native site and in a hydroponic culture under Cd treatments. In situ, the metallicolous (M) populations of both species hyperaccumulated Cd and Zn. The NM population of A. halleri hyperaccumulated Cd and Zn while the NM A. arenosa did not. In the hydroponic experiments, the NM populations of both species accumulated more Cd in their shoots than the M populations. Our research suggests that the two Arabidopsis species evolved different strategies of adaptation to extreme metallic environments that involve fine regulation of metal homeostasis, adjustment of the photosynthetic apparatus and accumulation of flavonols and anthocyanins.
Assuntos
Arabidopsis/metabolismo , Cádmio/toxicidade , Adaptação Fisiológica , Antocianinas/metabolismo , Arabidopsis/genética , Arabidopsis/fisiologia , Bioacumulação , Cádmio/metabolismo , Clorofila A/metabolismo , Flavonoides/metabolismo , Hidroponia , Fotossíntese , Ploidias , Estresse FisiológicoRESUMO
Plants produce a huge diversity of specialized metabolites (SM) throughout their life cycle that play important physiological and ecological functions. SM can protect plants and seeds against diseases, predators, and abiotic stresses, or support their interactions with beneficial or symbiotic organisms. They also have strong impacts on human nutrition and health. Despite this importance, the biosynthesis and biological functions of most of the SM remain elusive and their diversity and/or quantity have been reduced in most crops during domestication. Seeds present a large number of SM that are important for their physiological, agronomic, nutritional or industrial qualities and hence, provide interesting models for both studying biosynthesis and producing large amounts of specialized metabolites. For instance, phenolics are abundant and widely distributed in seeds. More specifically, flavonoid pathway has been instrumental for understanding environmental or developmental regulations of specialized metabolic pathways, at the molecular and cellular levels. Here, we summarize current knowledge on seed phenolics as model, and discuss how recent progresses in omics approaches could help to further characterize their diversity, regulations, and the underlying molecular mechanisms involved.
Assuntos
Fenóis/metabolismo , Sementes/metabolismo , Flavonoides/química , Flavonoides/metabolismo , Flavonoides/fisiologia , Redes e Vias Metabólicas , Fenóis/química , Sementes/fisiologiaRESUMO
Trace metal elements are essential for plant growth but become toxic at high concentrations, while some non-essential elements, such as Cd and As, show toxicity even in traces. Thus, metal homeostasis is tightly regulated in plants. Plant species colonising metalliferous soils have evolved mechanisms to hypertolerate metals and, in rare cases, can hyperaccumulate them in excess amounts in their shoots. The molecular mechanisms of metal hypertolerance and hyperaccumulation are likely derived from alterations in the basic mechanisms involved in general metal homeostasis. Genes involved in metal transport, synthesis of metal chelators and oxidative stress responses are constitutively and highly expressed in metal hypertolerant and hyperaccumulator species. Plant specialized metabolites and cell wall components have been proposed as major players in these mechanisms. In addition, the high intra-specific natural variation of metal hypertolerance and hyperaccumulation suggests that various molecular mechanisms might be involved in the evolution of these traits. To date, the potential of wild plant populations as systems to study metal tolerance and hyperaccumulation has not been fully exploited. The advent of next-generation sequencing (NGS) has enabled the study of non-model species, providing an opportunity to study natural populations and new tolerant and/or hyperaccumulating species, and will provide new insights into metal tolerance and hyperaccumulation. In this review we highlight background knowledge about metal tolerance and hyperaccumulation in plants and the current state-of-the-art techniques to study and identify the underlying mechanisms of metal hypertolerance and hyperaccumulation. We also outline for the reader the importance of the multidisciplinarity of this research field and how the integration of multiomic approaches will benefit facing the future scientific challenges.
Assuntos
Metais/metabolismo , Poluentes do Solo/metabolismo , Biodegradação Ambiental , Cádmio/metabolismo , Sequenciamento de Nucleotídeos em Larga EscalaRESUMO
The mechanisms underlying the response and adaptation of plants to excess of trace elements are not fully described. Here, we analysed the importance of protein lysine methylation for plants to cope with cadmium. We analysed the effect of cadmium on lysine-methylated proteins and protein lysine methyltransferases (KMTs) in two cadmium-sensitive species, Arabidopsis thaliana and A. lyrata, and in three populations of A. halleri with contrasting cadmium accumulation and tolerance traits. We showed that some proteins are differentially methylated at lysine residues in response to Cd and that a few genes coding KMTs are regulated by cadmium. Also, we showed that 9 out of 23 A. thaliana mutants disrupted in KMT genes have a tolerance to cadmium that is significantly different from that of wild-type seedlings. We further characterized two of these mutants, one was knocked out in the calmodulin lysine methyltransferase gene and displayed increased tolerance to cadmium, and the other was interrupted in a KMT gene of unknown function and showed a decreased capacity to cope with cadmium. Together, our results showed that lysine methylation of non-histone proteins is impacted by cadmium and that several methylation events are important for modulating the response of Arabidopsis plants to cadmium stress.
Assuntos
Adaptação Fisiológica , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/fisiologia , Cádmio/toxicidade , Lisina/metabolismo , Estresse Fisiológico , Adaptação Fisiológica/efeitos dos fármacos , Adaptação Fisiológica/genética , Sequência de Aminoácidos , Arabidopsis/efeitos dos fármacos , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Metilação , Metiltransferases/genética , Metiltransferases/metabolismo , Mutação/genética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genéticaRESUMO
OBJECTIVE: An inter and intra rater reliability (INTERR and INTRAR) study was designed. METHODS: 71 subjects, with primary hip coxarthrosis, were included and randomly divided in a study group (SG= 36) and a control group (CG= 35) to assess the efficacy of the Fascial Manipulation® (FM®) method. The primary objective was the assessment of INTERR and INTRAR about movement verification (MV) and palpation verification (PV) of FM® performed by two physiotherapists (PtA and PtB). The secondary objective was evaluate the efficacy of FM® through MV, PV and pain score. Pain was assessed using the Numeric Rating Scale (NRS). SG received three weekly sessions of FM® byPtA. PtB re-evaluated all the subjects at the end of the study. RESULTS: Results of the INTERR analysis showed for SG: MV (ICC= 0.92, k= 72.7%); PV (ICC= 0.91, k= 75.7%). For CG : MV (ICC= 0.95, k= 84.2%); PV (ICC= 0.90, k= 75%). Results of the INTRAR analysis for SG reported: MV (ICC= 0.82, k= 74,8%); PV (ICC= 0.60, k= 46.8%); for CG: MV (ICC= 0.93, k= 78.7%); PV (ICC= 0.84, k= 53.3%). Statistical significance were reported in NRS (p = 0.001), MV (p = 0.0003) and PV (p < 0.0001) with better results for SG using "Intention To Treat" method. DISCUSSION: This study demonstrates that FM® assessment procedures have a high reliability even if applied by practitioners with basic experience. Furthermore FM® treatment can improve pain and ROM in individuals with primary coxarthrosis.
Assuntos
Osteoartrite do Quadril , Fáscia , Humanos , Movimento , Osteoartrite do Quadril/diagnóstico , Osteoartrite do Quadril/terapia , Palpação , Reprodutibilidade dos TestesRESUMO
Hyperaccumulation and hypertolerance of Trace Metal Elements (TME) like Cd and Zn are highly variable in pseudo-metallophytes species. In this study we compared the impact of high Cd or Zn concentration on the photosynthetic apparatus of the Arabidopsis arenosa and Arabidopsis halleri pseudo-metallophytes growing on the same contaminated site in Piekary Slaskie in southern Poland. Plants were grown in hydroponic culture for 6 weeks, and then treated with 1.0 mM Cd or 5.0 mM Zn for 5 days. Chlorophyll a fluorescence and pigment content were measured after 0, 1, 2, 3, 4, and 5 days in plants grown in control and exposed to Cd or Zn treatments. Moreover, the effect of TME excess on the level of oxidative stress and gas-exchange parameters were investigated. In both plant species, exposure to high Cd or Zn induced a decrease in chlorophyll and an increase in anthocyanin contents in leaves compared to the control condition. After 5 days Cd treatment, energy absorbance, trapped energy flux and the percentage of active reaction centers decreased in both species. However, the dissipated energy flux in the leaves of A. arenosa was smaller than in A. halleri. Zn treatment had more toxic effect than Cd on electron transport in A. halleri compared with A. arenosa. A. arenosa plants treated with Zn excess did not react as strongly as in the Cd treatment and a decrease only in electron transport flux and percentage of active reaction centers compared with control was observed. The two species showed contrasting Cd and Zn accumulation. Cd concentration was almost 3-fold higher in A. arenosa leaves than in A. halleri. On the opposite, A. halleri leaves contained 3-fold higher Zn concentration than A. arenosa. In short, our results showed that the two Arabidopsis metallicolous populations are resistant to high Cd or Zn concentration, however, the photosynthetic apparatus responded differently to the toxic effects.
RESUMO
The molecular analysis of metal hyperaccumulation in species such as Arabidopsis halleri offers the chance to gain insights into metal homeostasis and into the evolution of adaptation to extreme habitats. A prerequisite of metal hyperaccumulation is metal hypertolerance. Genetic analysis of a backcross population derived from Arabidopsis lyrata × A. halleri crosses revealed three quantitative trait loci for Cd hypertolerance. A candidate gene for Cdtol2 is AhCAX1, encoding a vacuolar Ca2+ /H+ antiporter. We developed a method for the transformation of vegetatively propagated A. halleri plants and generated AhCAX1-silenced lines. Upon Cd2+ exposure, several-fold higher accumulation of reactive oxygen species (ROS) was detectable in roots of AhCAX1-silenced plants. In accordance with the dependence of Cdtol2 on external Ca2+ concentration, this phenotype was exclusively observed in low Ca2+ conditions. The effects of external Ca2+ on Cd accumulation cannot explain the phenotype as they were not influenced by the genotype. Our data strongly support the hypothesis that higher expression of CAX1 in A. halleri relative to other Arabidopsis species represents a Cd hypertolerance factor. We propose a function of AhCAX1 in preventing a positive feedback loop of Cd-elicited ROS production triggering further Ca2+ -dependent ROS accumulation.
Assuntos
Antiporters/fisiologia , Proteínas de Arabidopsis/fisiologia , Arabidopsis/metabolismo , Cádmio/farmacologia , Proteínas de Transporte de Cátions/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Antiporters/metabolismo , Arabidopsis/efeitos dos fármacos , Proteínas de Arabidopsis/metabolismo , Cálcio/metabolismo , Proteínas de Transporte de Cátions/metabolismo , Perfilação da Expressão Gênica , Plantas Geneticamente ModificadasRESUMO
Ca2+ signals in plant cells are important for adaptive responses to environmental stresses. Here, we report that the Arabidopsis CATION/Ca2+ EXCHANGER2 (CCX2), encoding a putative cation/Ca2+ exchanger that localizes to the endoplasmic reticulum (ER), is strongly induced by salt and osmotic stresses. Compared with the WT, AtCCX2 loss-of-function mutant was less tolerant to osmotic stress and displayed the most noteworthy phenotypes (less root/shoot growth) during salt stress. Conversely, AtCCX2 gain-of-function mutants were more tolerant to osmotic stress. In addition, AtCCX2 partially suppresses the Ca2+ sensitivity of K667 yeast triple mutant, characterized by Ca2+ uptake deficiency. Remarkably, Cameleon Ca2+ sensors revealed that the absence of AtCCX2 activity results in decreased cytosolic and increased ER Ca2+ concentrations in comparison with both WT and the gain-of-function mutants. This was observed in both salt and nonsalt osmotic stress conditions. It appears that AtCCX2 is directly involved in the control of Ca2+ fluxes between the ER and the cytosol, which plays a key role in the ability of plants to cope with osmotic stresses. To our knowledge, Atccx2 is unique as a plant mutant to show a measured alteration in ER Ca2+ concentrations. In this study, we identified the ER-localized AtCCX2 as a pivotal player in the regulation of ER Ca2+ dynamics that heavily influence plant growth upon salt and osmotic stress.
Assuntos
Antiporters/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Cálcio/metabolismo , Citosol/metabolismo , Retículo Endoplasmático/metabolismo , Antiporters/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Retículo Endoplasmático/genética , Regulação da Expressão Gênica de Plantas , Pressão Osmótica , Transporte Proteico , Transdução de SinaisRESUMO
While cadmium (Cd) tolerance is a constitutive trait in the Arabidopsis halleri species, Cd accumulation is highly variable. Recent adaptation to anthropogenic metal stress has occurred independently within the genetic units of A. halleri and the evolution of different mechanisms involved in Cd tolerance and accumulation has been suggested. To gain a better understanding of the mechanisms underlying Cd tolerance and accumulation in A. halleri, ionomic inductively coupled plasma mass spectrometry (ICP-MS), transcriptomic (RNA sequencing) and metabolomic (high-performance liquid chromatography-mass spectrometry) profiles were analysed in two A. halleri metallicolous populations from different genetic units (PL22 from Poland and I16 from Italy). The PL22 and I16 populations were both hypertolerant to Cd, but PL22 hyperaccumulated Cd while I16 behaved as an excluder both in situ and when grown hydroponically. The observed hyperaccumulator vs excluder behaviours were paralleled by large differences in the expression profiles of transporter genes. Flavonoid-related transcripts and metabolites were strikingly more abundant in PL22 than in I16 shoots. The role of novel A. halleri candidate genes possibly involved in Cd hyperaccumulation or exclusion was supported by the study of corresponding A. thaliana knockout mutants. Taken together, our results are suggestive of the evolution of divergent strategies for Cd uptake, transport and detoxification in different genetic units of A. halleri.
Assuntos
Arabidopsis/fisiologia , Cádmio/toxicidade , Antioxidantes/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Flavonoides/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Genes de Plantas , Metabolômica , Minerais/metabolismo , Modelos Biológicos , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/metabolismo , Análise de Componente Principal , Solo/química , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genética , Transcriptoma/efeitos dos fármacos , Transcriptoma/genéticaRESUMO
Zinc (Zn) hyperaccumulation and hypertolerance are highly variable traits in Arabidopsis halleri. Metallicolous populations have evolved from nearby nonmetallicolous populations in multiple independent adaptation events. To determine whether these events resulted in similar or divergent adaptive strategies to high soil Zn concentrations, we compared two A. halleri metallicolous populations from distant genetic units in Europe (Poland (PL22) and Italy (I16)). The ionomic (Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES)) and transcriptomic (RNA sequencing (RNA-Seq)) responses to growth at 5 and 150 µM Zn were analyzed in root and shoot tissues to examine the contribution of the geographic origin and treatment to variation among populations. These analyses were enabled by the generation of a reference A. halleri transcriptome assembly. The genetic unit accounted for the largest variation in the gene expression profile, whereas the two populations had contrasting Zn accumulation phenotypes and shared little common response to the Zn treatment. The PL22 population displayed an iron deficiency response at high Zn in roots and shoots, which may account for higher Zn accumulation. By contrast, I16, originating from a highly Zn-contaminated soil, strongly responded to control conditions. Our data suggest that distinct mechanisms support adaptation to high Zn in soils among A. halleri metallicolous populations.
Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Arabidopsis/fisiologia , Zinco/toxicidade , Adaptação Fisiológica/genética , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Clorofila/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Geografia , Homeostase , Ferro/metabolismo , Modelos Biológicos , Fenótipo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/metabolismo , Análise de Componente Principal , Transcriptoma/efeitos dos fármacos , Transcriptoma/genéticaRESUMO
Investigation of genetic determinants of Cd tolerance in the Zn/Cd hyperaccumulator Arabidopsis halleri allowed the identification of the vacuolar Ca(2+)/H(+) exchanger encoding CAX1 gene. CAX1 was proposed to interfere with the positive feedback loop between Reactive Oxygen Species (ROS) production and Cd-induced cytosolic Ca(2+) spikes, especially at low external Ca(2+) supply. In this study expression of genes involved in ROS homeostasis, cell wall composition, apoplastic pH regulation and Ca(2+) homeostasis were monitored in Arabidopsis thaliana wild-type and cax1-1 knock-out mutant and in Arabidopsis halleri wild-type exposed to cadmium or in control conditions. Clustering the outputs of the expression analysis in a gene co-expression network revealed that CAX1 and genes involved in Ca(2+) cellular homeostasis, apoplastic pH and oxidative stress response were highly correlated in A. thaliana, but not in A. halleri. Many of the studied genes were already highly expressed in A. halleri and/or their expression was not modified by exposure to Cd. The results further supported the role of CAX1 in the regulation of cytosolic ROS accumulation as well as the existence of different cell wall modifications strategies in response to Cd in Arabidopsis thaliana and halleri.