Luis E Hernandez - Academia.edu (original) (raw)

Papers by Luis E Hernandez

The Plant Cell, 2013

Stress constantly challenges plant adaptation to the environment. Of all stress types, arsenic wa... more Stress constantly challenges plant adaptation to the environment. Of all stress types, arsenic was a major threat during the early evolution of plants. The most prevalent chemical form of arsenic is arsenate, whose similarity to phosphate renders it easily incorporated into cells via the phosphate transporters. Here, we found that arsenate stress provokes a notable transposon burst in plants, in coordination with arsenate/phosphate transporter repression, which immediately restricts arsenate uptake. This repression was accompanied by delocalization of the phosphate transporter from the plasma membrane. When arsenate was removed, the system rapidly restored transcriptional expression and membrane localization of the transporter. We identify WRKY6 as an arsenate-responsive transcription factor that mediates arsenate/phosphate transporter gene expression and restricts arsenate-induced transposon activation. Plants therefore have a dual WRKY-dependent signaling mechanism that modulates arsenate uptake and transposon expression, providing a coordinated strategy for arsenate tolerance and transposon gene silencing.

Frontiers in Plant Science, 2022

Background and aims Mercury (Hg) is one of the most dangerous pollutant heavy metals to the envir... more Background and aims Mercury (Hg) is one of the most dangerous pollutant heavy metals to the environment, which causes several toxic effects in plants upon accumulation, such as induction of oxidative stress. Nitrogen (N) is one of the most limiting macronutrient for plants, being mostly assimilated as NO3─ which is reduced to NO2─ by the enzyme nitrate reductase (NR), prior its reduction to NH4+.Methods We studied the physiological alterations caused by Hg (0, 6 and 30 µM) in alfalfa plants grown at two different levels of NO3─: low, (2 mM; LN), and high (12 mM; HN) for one week using a semi-hydroponic culture system.Results Several parameters of oxidative stress such as lipid peroxidation, chlorophyll content, biothiol concentration and, ascorbate peroxidase (APX) and glutathione reductase (GR) activity showed that HN plants were less affected by Hg. Nitrate reductase activity and NO3─ concentration was altered under Hg stress, with lower impact in plants nourished with high NO3─. ...

Free radical biology & medicine, Jan 5, 2018

Reactive oxygen species (ROS) are by-products of aerobic metabolism, and excessive production can... more Reactive oxygen species (ROS) are by-products of aerobic metabolism, and excessive production can result in oxidative stress and cell damage. In addition, ROS function as cellular messengers, working as redox regulators in a multitude of biological processes. Understanding ROS signalling and stress responses requires methods for precise imaging and quantification to monitor local, subcellular and global ROS dynamics with high selectivity, sensitivity and spatiotemporal resolution. In this review, we summarize the present knowledge for in vivo plant ROS imaging and detection, using both chemical probes and fluorescent protein-based biosensors. Certain characteristics of plant tissues, for example high background autofluorescence in photosynthetic organs and the multitude of endogenous antioxidants, can interfere with ROS and redox potential detection, making imaging extra challenging. Novel methods and techniques to measure in vivo plant ROS and redox changes with better selectivity,...

Mercury (Hg) is one of the most harmful metals in nature. In plants, the accumulation of Hg produ... more Mercury (Hg) is one of the most harmful metals in nature. In plants, the accumulation of Hg produces diverse toxic effects, most of them caused by the strong affinity of Hg for sulfhydryl residues. In addition, the induction of oxidative stress is a well-known symptom of the Hg accumulation in plant cells. Previously we have shown the relevant role of the glutathione (GSH) metabolism in the responses to Hg (Sobrino-Plata et al. 2014a, 2014b). GSH contributes to the amelioration of reactive oxygen species (ROS) excess formed by different stresses. Likewise GSH is the precursor of phytochelatins (PCs), metal-chelating biothiols, and behaves as a major reservoir of non-protein reduced sulfur. In this study we worked with three -glutamylcysteine synthetase (-ECS) mutant alleles of Arabidopsis thaliana, which have different levels of GSH relative to wild type (Col-0): cad2-1 (30 %), pad2-1 (20 %) and rax1-1 (45 %). A fourth mutant was used, cad1-3, unable to produce PCs. These plants w...

One of the most hazardous metals to the environment is mercury (Hg), which accumulates in soils o... more One of the most hazardous metals to the environment is mercury (Hg), which accumulates in soils of Almadén (Spain); area that has the largest levels of environmental Hg in the World. A key component of Hg-detoxification in plants is the metabolism of glutathione (GSH), although some aspects need clarification. With this purpose, we studied the tolerance to Hg of two cadmium-sensitive Arabidopsis thaliana mutants: cad2-1, defective in GSH biosynthesis, and cad1-3, unable to synthesize phytochelatins (PCs). In a tolerance assay, where root growth inhibition was measured, mutant seedlings presented double inhibition than the wild type (Col-0) when were treated with 10 µM Hg. HPLC and HPLC-ESI-TOFMS analysis were used to identify and quantify biothiols in the different treatments applied in the plants. Production of PCs was observed in wild type, and in a very low level in cad2-1, similar to the values found of GSH. In cad1-3 plants there was not accumulation of PCs, but the concentrati...

Journal of experimental botany, Jan 5, 2015

The accumulation of toxic metals and metalloids, such as cadmium (Cd), mercury (Hg), or arsenic (... more The accumulation of toxic metals and metalloids, such as cadmium (Cd), mercury (Hg), or arsenic (As), as a consequence of various anthropogenic activities, poses a serious threat to the environment and human health. The ability of plants to take up mineral nutrients from the soil can be exploited to develop phytoremediation technologies able to alleviate the negative impact of toxic elements in terrestrial ecosystems. However, we must select plant species or populations capable of tolerating exposure to hazardous elements. The tolerance of plant cells to toxic elements is highly dependent on glutathione (GSH) metabolism. GSH is a biothiol tripeptide that plays a fundamental dual role: first, as an antioxidant to mitigate the redox imbalance caused by toxic metal(loid) accumulation, and second as a precursor of phytochelatins (PCs), ligand peptides that limit the free ion cellular concentration of those pollutants. The sulphur assimilation pathway, synthesis of GSH, and production of...

The genus Atriplex is spread out in all continents, except Antarctica, and includes many species ... more The genus Atriplex is spread out in all continents, except Antarctica, and includes many species useful for rehabilitation of degraded soil, revegetation and animal production. Atriplex exhibits a high morphological and physiological variability that can be used to establish genetic relationships between species and populations. Variability is an important feature to select Atriplex genotypes adapted to harsh conditions, but it also strongly affects the data reproducibility of genetic analysis. Molecular markers offer an effective tool for estimation of genetic diversity. Random Amplified Polymorphic DNAs (RAPDs) have being extensively used as highly polymorphic molecular markers. We used thirteen primers (1) to assess genetic variation of forty individual plants of eight Moroccan Atriplex species. To assure RAPD pattern reproducibility some reactions were repeated three times. Amplification rendered 220 intense bands that were scored as present or absent across all species, with 11 to 21 bands for each primer. 95% of the loci revealed to be highly polymorphic, indicating that RAPDs are an abundant source of polymorphic markers in Atriplex species. The results obtained show that RAPD variability was mostly at inter-specific level, being the intra-specific variability much lower. The RAPD analysis reported here confirms previous studies made using morphological and isozyme markers. It also proved to be a reliable and fast tool for assessing the genetic diversity of Atriplex.

Plant Cell Reports, 2003

We have explored the transient over-expression of Arabidopsis thaliana ascorbate peroxidase 3 (AP... more We have explored the transient over-expression of Arabidopsis thaliana ascorbate peroxidase 3 (APX3) in Nicotiana benthamiana using a viral vector based on the potato virus X (PVX). Plants infected with a PVX:APX3 hybrid had a similar progression of viral particles compared to control plants infected with a PVX:GFP hybrid, indicating that infection was not affected by the over-expression of heterologous APX3. Our results also showed that in PVX:APX3-infected plants, the hybrid virus directed a high level of APX3 expression and the recombinant protein was functional, as inferred from the higher APX activity compared to mock and PVX:GFP hybrid-infected plants. The PVX recombinant expression system used is a simple and quick method for transient expression of heterologous APXs, which are expected to suffer specific processing in plant cells.

RSC Advances, 2013

ABSTRACT Specific stress responses to cadmium, arsenic and mercury appear in the metallophyte Sil... more ABSTRACT Specific stress responses to cadmium, arsenic and mercury appear in the metallophyte Silene vulgaris when grown hydroponically3 The tolerance of the metallophyte Silene vulgaris, a plant suitable for the phytostabilisation of metal(loid)-contaminated soils, to arsenic (As), mercury (Hg) and cadmium (Cd) was evaluated in a semi-hydroponic culture system under controlled environmental conditions. The appearance of oxidative stress, alteration of photochemical processes and modification of biothiol content were studied as physiological parameters of metal(loid) stress in plants treated with 0, 6 and 30 mM (As, Hg or Cd) for 7 days. In spite of the metal(loid) excluder behaviour of S. vulgaris, Cd was translocated to the aerial part of the plant at a higher rate than Hg or As. The major toxic effects were observed in roots, where lipid peroxidation was increased in a dose-dependent manner. Redox enzymes such as glutathione reductase (GR) were severely inhibited by Hg, whereas GR was overexpressed. The accumulation of Cd produced a remarkable production of phytochelatins (PCs) in roots, whereas Hg and As led to modest PCs synthesis. There was a severe loss of chlorophyll content in Cd-treated plants, accompanied with a significant decrease in photosystem II efficiency (WPSII) and photochemical quenching (qP). Similar negative effects were observed in Hg-and As-exposed plants, but to a lesser degree. The exposure to the highest dose of each toxic element (30 mM) caused depletion of the light harvesting complex b1 protein. In conclusion, specific stress signatures to each metal(loid) were observed, with As being the least toxic element, suggesting that different mechanisms of tolerance were exerted. These results could be applied in future experiments to select tolerant ecotypes to optimize the phytostabilisation of metal(loid) multipolluted soils.

Plant physiology and biochemistry : PPB / Société française de physiologie végétale, 2014

This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mecha... more This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mechanisms of cadmium (Cd)-induced detoxification (i.e. chelation and antioxidative defence). A kinetic study was conducted on hydroponically grown Arabidopsis thaliana (L. Heyhn) to gain insight into the early events after exposure to Cd. Cadmium detoxification was investigated at different levels, including gene transcripts, enzyme activities and metabolite content. Data indicate a time-dependent response both within roots and between plant organs. Early on in roots, GSH was preferentially allocated to phytochelatin (PC) synthesis destined for Cd chelation. This led to decreased GSH levels, without alternative pathways activated to complement…

Plant Science, 2015

The induction of oxidative stress is a characteristic symptom of metal phytotoxicity and is count... more The induction of oxidative stress is a characteristic symptom of metal phytotoxicity and is counteracted by antioxidants such as glutathione (GSH) or homoglutathione (hGSH). The depletion of GSH│hGSH in fifteen-day-old alfalfa (Medicago sativa) plants pre-incubated with 1mM buthionine sulfoximine (BSO) affected antioxidant responses in a metal-specific manner under exposure to copper (Cu; 0, 6, 30 and 100μM) or cadmium (Cd; 0, 6 and 30μM) for 7 days. The phytotoxic symptoms observed with excess Cu were accompanied by an inhibition of root glutathione reductase (GR) activity, a response that was augmented in Cd-treated plants but reverted when combined with BSO. The synthesis of phytochelatins (PCs) was induced by Cd, whereas the biothiol concentration decreased in Cu-treated plants, which did not accumulate PCs. The depletion of GSH│hGSH by BSO also produced a strong induction of oxidative stress under excess Cu stress, primarily due to impaired GSH│hGSH-dependent redox homeostasis. In addition, the synthesis of PCs was required for Cd detoxification, apparently also determining the distribution of Cd in plants, as less metal was translocated to the shoots in BSO-incubated plants. Therefore, specific GSH│hGSH-associated mechanisms of tolerance were triggered by stress due to each metal.

Scientia Horticulturae, 2008

ABSTRACT Variability related to RAPD markers and sequences of nrDNA ITS region has been studied i... more ABSTRACT Variability related to RAPD markers and sequences of nrDNA ITS region has been studied in seven species of the genus Atriplex (A. amnicola, A. canescens, A. halimus from Morocco (MAR) and from USA, A. lentiformis, A. nummularia, A. semibaccata and A. undulate). As a whole, the results show a high variability among the species. The biggest diversity was obtained by RAPD data, followed by ITSs. According to RAPD markers, two major groups can be distinguished, one formed by A. semibaccata and A. undulata, the least similar to the rest of species. A. lentiformis was closer to A. halimus. Phylogenetic analysis confirmed the divergence of A. semibaccata from all species and the closeness of A. lentiformis to A. halimus. The intraspecies variability was also high, as 39 individual RAPD haplotypes were obtained by analyzing 40 plants. Genetic diversity was bigger among species (60.23%) than among individuals (39.77%). The amplification of ITS region leads to three well-defined clades. The heterogeneous and larger clade includes all A. amnicola individuals and some individuals from A. nummularia, A. lentiformis, A. halimus USA, A. halilmus MAR and A. undulata. Both RAPDs and ITS analyses revealed with some exceptions, that all individuals from one species grouped together. RAPDS turn out to be more appropriate than ITS to differentiate Atriplex species. The two markers gave rise to the same species relationships, but to a different structure of the Atriplex genetic diversity. AMOVA analysis estimated interspecies differences for 11.20% of the total ITS variation.Both the great variability and the apparently restrictive gene flow among the species are discussed considering the life history and characteristics of the plants studied.

Plant and Soil, 2014

ABSTRACT Background Glutathione (GSH) plays a dual role under heavy metal stress, as antioxidant ... more ABSTRACT Background Glutathione (GSH) plays a dual role under heavy metal stress, as antioxidant metabolite and as precursor of phytochelatins (PCs). Studying the responses of the GSH metabolism to heavy metals is important to improve tolerance. Methods We studied the oxidative stress signature of three -glutamylcysteine synthetase (ECS) Arabidopsis thaliana allele mutants (rax1-1, cad2-1, and pad2-1), first enzymatic step in the GSH synthetic pathway, when treated with 10 µM Cd or Hg for 72 h. Results GSH concentration was lower in the mutants (45% rax1-1; 30% cad2-1; and 20% pad2-1), which was also associated with inferior translocation of Cd or Hg to shoots, than in wild type Col-0. Glutathione reductase (GR) and NADPH-oxidase activities were inhibited in roots, phytotoxic effects consistently more pronounced in the mutants, particularly in pad2-1. Non-photochemical quenching augmented with exposure time to Cd or Hg in Col-0, but not so in the ECS mutants. Mercury caused severe damage in cad2-1 and pad2-1 root proteins profile; toxic effects confirmed by GR and H+-ATPase immunodetection. PCs appeared in Col-0 roots under metal stress, and surprisingly accumulated in rax1-1. ECS immunodetection revealed its overexpression in rax1-1. Conclusion A minimum amount of GSH may be required for adequate metal tolerance, where ECS expression could compensate GSH deficiency under stress.

Metallomics, 2014

El artículo seleccionado no se encuentra disponible por ahora a texto completo por no haber sido ... more El artículo seleccionado no se encuentra disponible por ahora a texto completo por no haber sido facilitado todavía por el investigador a cargo del archivo del mismo.

Journal of Hazardous Materials, 2021

Toxic metals such as cadmium (Cd) and mercury (Hg) represent a threat to photosynthetic organisms... more Toxic metals such as cadmium (Cd) and mercury (Hg) represent a threat to photosynthetic organisms of polluted aquatic ecosystems, and knowledge about mechanisms of toxicity is essential for appropriate assessment of environmental risks. We used Synchrotron Radiation-Fourier Transformed Infrared microspectroscopy (μSR-FTIR) to characterise major changes of biomolecules caused by Cd and Hg in the model green microalga Chlamydomonas reinhardtii. μSR-FTIR showed several metabolic alterations in different biochemical groups such as carbohydrates, proteins, and lipids in a time-dose dependent manner, with the strongest changes occurring at concentrations above 10 μM Cd and 15 μM Hg after short-term (24 h) treatments. This occurred in a context where metals triggered intracellular oxidative stress and chloroplast damage, along with autophagy induction by overexpressing AUTOPHAGY-RELATED PROTEIN 8 (ATG8). Thin layer chromatography analysis confirmed that toxic metals promoted remarkable changes in lipid profile, with higher degree of esterified fatty acid unsaturation as detected by gas chromatography coupled with mass spectrometry. Under Cd stress, there was specifically higher unsaturation of free fatty acids, while Hg led to stronger unsaturation in monogalactosyldiacylglycerol. μSR-FTIR spectroscopy proved as a valuable tool to identify biochemical alterations in microalgae, information that could be exploited to optimise approaches for metal decontamination.