Increase of Total Glutathione as a Response to Cd Induced Stress in a Chilean Endemic Bryophytes (Thuidium Sp.)

Abstract

Bryophytes collected from the IV Region of Chile, were treated with CdCl 2 to stimulate the synthesis of phytochelants. After cadmium treatment, total peptides were extracted from the plants and were analyzed using HPLC to search for the presence of phytochelatin molecules.Chromatography results showed the absence of phytochelatin-like molecules in bryophytes. However, glutathione and a molecule suspected to be γ-glutamilcistein were detected. The latter compound is knowed to be involved in the metabolic pathway of the gluthatione and phytochelatin synthesis.The results indicated the absence of detectable phytochelatins in bryophytes containing heavy metal as contaminants. The increase in glutathione during the experimental period may have been due to a response to oxidative stress. Thus this work suggests an important role of the glutathione in the detoxification mechanisms of bryophytes.Key words: Bryophytes, glutathione, chromatography, oxidative stress. INTRODUCTONContamination is currently one of the most studied phenomena. Elevated concentrations of heavy metals, of natural or anthropogenic origin, are one of the most difficult contaminants to study 1 . However there are organisms, like a large variety of plants, which are resistant to high levels of heavy metals 2,3 . Research in these organisms resistant to heavy metals have found the presence of compounds synthesized at intra-cellular level, which are capable of immobilizing these elements. Because of their ability to store metals, these organisms have been considered as an alternative to be used as bio-monitors or biological extractors at contaminated sites 4,5,6,7 .The phytochelatins and the glutathione compose a class of compounds generated by plants in response to heavy metals. These phylochelatins are a family of peptides that have been identified in plants and some microorganisms. Phytochelatins have a primary structure of (γ-glutamil-cysteine) n glycine, with n=2-11 8,9,10 . They are synthesized from glutathione, which is a tripeptide formed by glutamic acid, cysteine and glycine (γ-glutamil-cisteinilglycine). Glutathione also plays an important role in the response of plants to environmental stress, oxidative stress and that produced by xenobiotic compounds such as heavy metals 4,6,11 . Phytochelatins have been described in different types of organisms such as plants, nematodes, algae and yeasts 3,12 . Some studies have demonstrated that bryophytes (mosses) do not form phylochelatins, but only their precursor glutathione 5,11 .Considering that bryophytes have been described as organisms which are particularly reactive to contaminants and thus may have an important role as bio-indicators of environmental contamination 5,13,14,15,16,17 , this contribution examined the presence of phytochelants in endemic Chilean mosses challenged with a heavy metal, cadmium, by means of high-pressure liquid chromatography (HPLC). EXPERIMENTAL Collection and maintenance of mossesMosses were collected from the area of Alcohuas in the IV Region of Chile (Figu...

BIOMONITOREO ACTIVO CON Leskea angustata EN LA ZONA METROPOLITANA DEL VALLE DE TOLUCA

“…Por otro lado, a diferencia de las plantas superiores, en musgos, el GHS participa en una gran variedad de procesos y puede desempeñar un papel esencial en la destoxificación por metales divalentes, la cual se caracteriza por un aumento del grupo de GSH con o sin evidencia de participación de PC (Bruns et al 2001, Saxena et al 2003, Bleuel et al 2005, Braha et al 2007, Rau et al 2007, Leinenweber et al 2009). En este estudio se observó un aumento estadístico significativo en la concentración de GHS (Cuadro III); sin embargo, la concentración de PC fue menor al límite de detección (0.2 nM/g).…”

“…En los últimos años se ha investigado el metabolismo del azufre, en particular del GSH, que es un tripéptido formado por glutamato (γ-Glu), cisteína (Cys) y glicina (Gly), ya que participa en muchos de los procesos metabólicos de una célula vegetal y es un componente esencial del sistema antioxidante que controla las especies reactivas de oxígeno y el grupo tiol (-SH) de la cisteína; está relacionado con la quelación de xenobióticos y metales pesados. A diferencia de las plantas superiores, en las briofitas el GSH parece desempeñar un papel fundamental en la desintoxicación de metales mediante el transporte de éstos a través del citoplasma (Bruns et al 2001, Saxena et al 2003, Bleuel et al 2005, Braha et al 2007, Rau et al 2007, Leinenweber et al 2009, Emamverdian et al 2015.…”

Levels of Antioxidant Compound Glutathione in Moss from Industrial Areas

“…Although cysteine-rich heavy metal-binding peptides, metallothioneins, organic acids, amino acids, and glutathione can carry out this function, in most eukaryotes it is generally carried out by PCs. However, in bryophytes it appears that the function is mainly carried out by glutathione [10,25,26,28]. Thus, mosses living in environments that are characterised by high levels of metals are expected to have higher concentrations of glutathione than mosses living in areas characterised by low levels of metals.…”

“…Although different authors have questioned the role of PCs in the development of heavy metal tolerance due to the energy costs that are associated with sulphate reduction and PC synthesis [21,22], in many cases under stress conditions, plant cells contain a high concentration of PCs and a low concentration of glutathione [23,24]. Nevertheless, unlike in higher plants, the synthesis of PCs has not been observed for most bryophytes in response to high levels of heavy metals [10,23,25,26]. Researchers investigating the glutathione response in terrestrial and aquatic mosses have observed increased glutathione concentrations, however not PC concentrations, in mosses that have been exposed to high concentrations of Cd, Ni, and Pb [10][11][12]25,27].…”

Responses to Cadmium in Early-Diverging Streptophytes (Charophytes and Bryophytes): Current Views and Potential Applications

“…Apo-PCn (complexes without Cd ions) may be degraded by vacuolar hydrolases and/or return to the cytosol, where they can continue to carry out their shuttling role [ 10 ]. Although it was thought for long time that bryophytes do not synthesize PCn under metal stress [ 55 , 57 , 100 , 101 , 102 ], Petraglia et al [ 103 ] demonstrated instead that constitutively expressed and functional PCSs are present in a number of bryophytes, as well as in other early-diverging streptophytes, arguing that the ability to synthesize PCn, as well as the presence of active PCSs, are ancestral (plesiomorphic) traits of early-diverging plants [ 103 ]. This study was followed by others, supporting the idea that PCn synthesis is an important mechanism of intracellular Cd detoxification, both in bryophytes, such as in L. riparium [ 62 ], L. cruciata [ 75 , 104 ], M. polymorpha [ 105 , 106 ], and in charophytes, such as N. mucronata [ 77 ].…”