RESUMEN
BACKGROUND: Natural populations of Arabidopsis thaliana exhibit phenotypic variations in specific environments and growth conditions. However, this variation has not been explored after seed osmopriming treatments. The natural variation in biomass production and root system architecture (RSA) was investigated across the Arabidopsis thaliana core collection in response to the pre-sawing seed treatments by osmopriming, with and without melatonin (Mel). The goal was to identify and characterize physiologically contrasting ecotypes. RESULTS: Variability in RSA parameters in response to PEG-6000 seed osmopriming with and without Mel was observed across Arabidopsis thaliana ecotypes with especially positive impact of Mel addition under both control and 100 mM NaCl stress conditions. Two ecotypes, Can-0 and Kn-0, exhibited contrasted root phenotypes: seed osmopriming with and without Mel reduced the root growth of Can-0 plants while enhancing it in Kn-0 ones under both control and salt stress conditions. To understand the stress responses in these two ecotypes, main stress markers as well as physiological analyses were assessed in shoots and roots. Although the effect of Mel addition was evident in both ecotypes, its protective effect was more pronounced in Kn-0. Antioxidant enzymes were induced by osmopriming with Mel in both ecotypes, but Kn-0 was characterized by a higher responsiveness, especially in the activities of peroxidases in roots. Kn-0 plants experienced lower oxidative stress, and salt-induced ROS accumulation was reduced by osmopriming with Mel. In contrast, Can-0 exhibited lower enzyme activities but the accumulation of proline in its organs was particularly high. In both ecotypes, a greater response of antioxidant enzymes and proline accumulation was observed compared to mechanisms involving the reduction of Na+ content and prevention of K+ efflux. CONCLUSIONS: In contrast to Can-0, Kn-0 plants grown from seeds osmoprimed with and without Mel displayed a lower root sensitivity to NaCl-induced oxidative stress. The opposite root growth patterns, enhanced by osmopriming treatments might result from different protective mechanisms employed by these two ecotypes which in turn result from adaptive strategies proper to specific habitats from which Can-0 and Kn-0 originate. The isolation of contrasting phenotypes paves the way for the identification of genetic factors affecting osmopriming efficiency.
Asunto(s)
Arabidopsis , Ecotipo , Melatonina , Raíces de Plantas , Estrés Salino , Melatonina/metabolismo , Arabidopsis/fisiología , Arabidopsis/crecimiento & desarrollo , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Raíces de Plantas/fisiología , Semillas/efectos de los fármacos , Semillas/crecimiento & desarrollo , Semillas/fisiología , Semillas/metabolismo , Antioxidantes/metabolismoRESUMEN
The mitotic checkpoint (MC) guards faithful sister chromatid segregation by monitoring the attachment of spindle microtubules to the kinetochores. When chromosome attachment errors are detected, MC delays the metaphase-to-anaphase transition through the inhibition of the anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase. In contrast to yeast and mammals, our knowledge on the proteins involved in MC in plants is scarce. Transient synchronization of root tips as well as promoter-reporter gene fusions were performed to analyze temporal and spatial expression of COPPER MODIFIED RESISTANCE1/PATRONUS1 (CMR1/PANS1) in developing Arabidopsis thaliana seedlings. Functional analysis of the gene was carried out, including CYCB1;2 stability in CMR1/PANS1 knockout and overexpressor background as well as metaphase-anaphase chromosome status. CMR1/PANS1 is transcriptionally active during M phase. Its deficiency provokes premature cell cycle exit and in consequence a rapid consumption of the number of meristematic cells in particular under stress conditions that are known to affect spindle microtubules. Root growth impairment is correlated with a failure to delay the onset of anaphase, resulting in anaphase bridges and chromosome missegregation. CMR1/PANS1 overexpression stabilizes the mitotic CYCB1;2 protein. Likely, CMR1/PANS1 coordinates mitotic cell cycle progression by acting as an APC/C inhibitor and plays a key role in growth adaptation to stress.
Asunto(s)
Adaptación Fisiológica , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Ciclo Celular/metabolismo , Aberraciones Cromosómicas , Anafase , Ciclosoma-Complejo Promotor de la Anafase/metabolismo , Arabidopsis/citología , Arabidopsis/fisiología , Proteínas de Arabidopsis/genética , Proteínas de Ciclo Celular/genética , División Celular , Cobre/metabolismo , Técnicas de Inactivación de Genes , Genes Reporteros , Cinetocoros , Meristema/citología , Meristema/genética , Meristema/fisiología , Metafase , Mitosis , Mutación , Fenotipo , Raíces de Plantas/citología , Raíces de Plantas/genética , Raíces de Plantas/fisiología , Estrés FisiológicoRESUMEN
Certain molecular mechanisms of Cd tolerance and accumulation have been identified in the model species Arabidopsis halleri, while intraspecific variability of these traits and the mechanisms of shoot detoxification were little addressed. The Cd tolerance and accumulation of metallicolous and non-metallicolous A. halleri populations from different genetic units were tested in controlled conditions. In addition, changes in shoot cell wall composition were investigated using Fourier transform infrared spectroscopy. Indeed, recent works on A. halleri suggest Cd sequestration both inside cells and in the cell wall/apoplast. All A. halleri populations tested were hypertolerant to Cd, and the metallicolous populations were on average the most tolerant. Accumulation was highly variable between and within populations, and populations that were non-accumulators of Cd were identified. The effect of Cd on the cell wall composition was quite similar in the sensitive species A. lyrata and in A. halleri individuals; the pectin/polysaccharide content of cell walls seems to increase after Cd treatment. Nevertheless, the changes induced by Cd were more pronounced in the less tolerant individuals, leading to a correlation between the level of tolerance and the extent of modifications. This work demonstrated that Cd tolerance and accumulation are highly variable traits in A. halleri, suggesting adaptation at the local scale and involvement of various molecular mechanisms. While in non-metallicolous populations drastic modifications of the cell wall occur due to higher Cd toxicity and/or Cd immobilization in this compartment, the increased tolerance of metallicolous populations probably involves other mechanisms such as vacuolar sequestration.
Asunto(s)
Arabidopsis/genética , Cadmio/metabolismo , Pared Celular/efectos de los fármacos , Variación Genética , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Biomasa , Cadmio/toxicidad , Pared Celular/metabolismo , Hibridación Genética , Hidroponía , Brotes de la Planta/efectos de los fármacos , Brotes de la Planta/genética , Brotes de la Planta/metabolismo , Análisis de Componente Principal , Especificidad de la Especie , Espectroscopía Infrarroja por Transformada de Fourier , Estrés FisiológicoRESUMEN
The exposure of plants to high concentrations of trace metallic elements such as copper involves a remodeling of the root system, characterized by a primary root growth inhibition and an increase in the lateral root density. These characteristics constitute easy and suitable markers for screening mutants altered in their response to copper excess. A forward genetic approach was undertaken in order to discover novel genetic factors involved in the response to copper excess. A Cu(2+) -sensitive mutant named copper modified resistance1 (cmr1) was isolated and a causative mutation in the CMR1 gene was identified by using positional cloning and next-generation sequencing. CMR1 encodes a plant-specific protein of unknown function. The analysis of the cmr1 mutant indicates that the CMR1 protein is required for optimal growth under normal conditions and has an essential role in the stress response. Impairment of the CMR1 activity alters root growth through aberrant activity of the root meristem, and modifies potassium concentration and hormonal balance (ethylene production and auxin accumulation). Our data support a putative role for CMR1 in cell division regulation and meristem maintenance. Research on the role of CMR1 will contribute to the understanding of the plasticity of plants in response to changing environments.
Asunto(s)
Adaptación Fisiológica/genética , Arabidopsis/genética , Arabidopsis/fisiología , Estrés Fisiológico/genética , Adaptación Fisiológica/efectos de los fármacos , Alelos , Arabidopsis/efectos de los fármacos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Núcleo Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Simulación por Computador , Cobre/toxicidad , ADN Bacteriano/genética , Genes de Plantas/genética , Proteínas Fluorescentes Verdes/metabolismo , Mutación/genética , Fenotipo , Reguladores del Crecimiento de las Plantas/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Sodio/metabolismo , Estrés Fisiológico/efectos de los fármacos , Fracciones Subcelulares/efectos de los fármacos , Fracciones Subcelulares/metabolismoRESUMEN
On sols highly polluted by trace metallic elements the majority of plant species are excluders, limiting the entry and the root to shoot translocation of trace metals. However a rare class of plants called hyperaccumulators possess remarkable adaptation because those plants combine extremely high tolerance degrees and foliar accumulation of trace elements. Hyperaccumulators have recently gained considerable interest, because of their potential use in phytoremediation, phytomining and biofortification. On a more fundamental point of view hyperaccumulators of trace metals are case studies to understand metal homeostasis and detoxification mechanisms. Hyperaccumulation of trace metals usually depends on the enhancement of at least four processes, which are the absorption from the soil, the loading in the xylem in the roots and the unloading from the xylem in the leaves and the detoxification in the shoot. Cadmium is one of the most toxic trace metallic elements for living organisms and its accumulation in the environment is recognized as a worldwide concern. To date, only nine species have been recognized as Cd hyperaccumulators that is to say able to tolerate and accumulate more than 0.01 % Cd in shoot dry biomass. Among these species, four belong to the Brassicaceae family with Arabidopsis halleri and Noccaea caerulescens being considered as models. An update of our knowledge on the evolution of hyperaccumulators will be presented here.
Asunto(s)
Cadmio/metabolismo , Cadmio/toxicidad , Plantas/efectos de los fármacos , Plantas/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismoRESUMEN
Nitrogen fertilization increases crop yield but excessive nitrate use can be a major environmental problem due to soil leaching or greenhouse gas emission. Root traits have been seldom considered as selection criteria to improve Nitrogen Use Efficiency of crops, due to the difficulty of measuring root traits under field conditions. Nonetheless, learning about mechanisms of lateral root (LR) growth stimulation or repression by nitrate availability could help to redesign root system architecture (RSA), a strategy aimed at developing plants with a dense and profound root system and with higher N uptake efficiency. Here, we explored the genetic diversity provided by natural populations of the model species Arabidopsis thaliana to identify potentially adaptive differences in biomass production and root morphology in response to nitrate availability. A core collection of 24 accessions that maximizes the genetic diversity within the species and Col-0 (the reference accession) were grown vertically on agar medium at moderate (N+) nitrate level for 6 days and then transferred to the same condition or to low (N-) nitrate concentration for 7 days. There was a major nutritional effect on the shoot biomass and root to shoot biomass ratio. The variation of the root biomass and RSA traits (primary root length, LRs number, LR mean length, total LRs length and LR densities) was primarily genetically determined. Differences in RSA traits between accessions were somewhat more pronounced at N-. Some accessions produced almost no visible LRs (Pyl-1, N13) at N-, while other produced up to a dozen (Kn-0). Taken together our data illustrate that natural variation exists within Arabidopsis for the studied traits. The identification of RSA ideotypes in the N response will facilitate further analysis of quantitative traits for root morphology.
Asunto(s)
Arabidopsis/crecimiento & desarrollo , Nitrógeno/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Brotes de la Planta/crecimiento & desarrollo , Arabidopsis/genética , Arabidopsis/metabolismo , Biomasa , Variación Genética , Nitratos/farmacología , Fenotipo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Brotes de la Planta/efectos de los fármacos , Brotes de la Planta/genética , Brotes de la Planta/metabolismo , Suelo/químicaRESUMEN
In all land plants, cellulose is synthesized from hexameric plasma membrane complexes. Indirect evidence suggests that in vascular plants the complexes involved in primary wall synthesis contain three distinct cellulose synthase catalytic subunits (CESAs). In this study, we show that CESA3 and CESA6 fused to GFP are expressed in the same cells and at the same time in the hypocotyl of etiolated seedlings and migrate with comparable velocities along linear trajectories at the cell surface. We also show that CESA3 and CESA6 can be coimmunoprecipitated from detergent-solubilized extracts, their protein levels decrease in mutants for either CESA3, CESA6, or CESA1 and CESA3, CESA6 and also CESA1 can physically interact in vivo as shown by bimolecular fluorescence complementation. We also demonstrate that CESA6-related CESA5 and CESA2 are partially, but not completely, redundant with CESA6 and most likely compete with CESA6 for the same position in the cellulose synthesis complex. Using promoter-beta-glucuronidase fusions we show that CESA5, CESA6, and CESA2 have distinct overlapping expression patterns in hypocotyl and root corresponding to different stages of cellular development. Together, these data provide evidence for the existence of binding sites for three distinct CESA subunits in primary wall cellulose synthase complexes, with two positions being invariably occupied by CESA1 and CESA3, whereas at least three isoforms compete for the third position. Participation of the latter three isoforms might fine-tune the CESA complexes for the deposition of microfibrils at distinct cellular growth stages.