The website DEHA is a tool (database) for the analysis of transcriptional factors in the genome of Debaryomyces hansenii, a yeast whose genome has been sequenced (Génolevures: www.igenolevures.org) but the most basic aspects of transcription regulation are unknown. To generate this tool we use the information available from the FT of the yeast Saccharomyces cerevisiae, which is the basic biological model for the study of different cellular processes, including the study of transcriptional factors.
Debaryomyces hansenii is a yeast that is characterized by its high tolerance to the high presence of salts in the medium, specifically at sodium concentrations, being able to live in media with NaCl concentrations up to 4M (Norkrans and Kylin 1969; Adler et al., 1985; Lucas et al., 1990; Gupta, 1996) and also in media with high pH (Norkrans, 1968). By supporting high sodium concentrations, D. hansenii is considered an unconventional yeast of commercial and biotechnological interest for agriculture and medicine, because the genes that allow it to survive in high concentrations of sodium can be used in the improvement of crop plants in so-called salty soils or for the application of gene therapy in degenerative diseases. D. hansenii has osmoregulation as the main strategy for adaptation to saline stress. This strategy consists mainly of: i) the expulsion of sodium out of the cell, through transport proteins such as ATPase Ena1p; and ii) the synthesis of compatible organic compounds such as glycerol or trehalose sugar. These compatible organic compounds, allow that in the presence of elevated intracellular sodium, the enzymes carry out their metabolic functions and cellular maintenance.
The Transcription Factors (TF), are part of the proteins that regulate transcription, that is, they can activate or repress it. This modulation occurs by its union or dissociation to short segments of DNA, as well as by its interaction with other proteins. To achieve these junctions, FTs have multiple domains, recognition and stability of DNA binding, interaction with other transcriptional factors or enzymes that modify histones, as well as binding to RNA polymerase, to facilitate or disfavor its assembly on the site of the beginning of the transcription.
The fact that FTs have more than one interaction or binding domain makes them form enormous complexes of pre or initiation of transcription, such as the SAGA transcriptional complex of yeasts, which can be formed by different proteins and can bind to different FT (Stener and Berger, 2000).
Outline of the SAGA transcriptional complex of yeasts. Modified figure by Stener and Berger (2000).
The binding of TF to DNA is either electrostatic or by Van der Waals forces (occasionally they can be hydrogen bonds). This interaction allows the binding of the transcriptional factor to the DNA to be specific, that is, that each FT corresponds to only one DNA sequence; these sequences are short and are referred to as consensus binding sequences, for example, the mammalian transcription factor NFkb recognizes and binds to the nucleotide sequence (5'-GGGACTTTCC-3 ') in the promoter region of genes encoding inflammatory response proteins. The promoter region is designated by convention at 1000 base pairs before the start codon (ATG) of each gene and may contain one or more sequences specific for one or more FT.
Scheme representation of the promoter region of a gene. The rectangles represent the transcriptional factors attached to the sites or specific binding sequences in the DNA of the promoter region of a gene.
Sterner D and Berger SL. (2000). Acetylation of Histones and Transcription-Related Factors. Microbiology and Molecular Biology Reviews; 64 (2): 435-459.
Extremophile organisms are those that survive and grow in environments of physicochemical conditions considered extreme or limiting, compared to the normal conditions in which most organisms live. To survive in such conditions, extremophiles have developed unique adaptations, mainly at the level of their membranes and macromolecules.
There are eukaryotic organisms such as fish, invertebrates, yeasts, fungi and plants that have partially colonized habitats of extreme conditions, which is why they are called tolerant, in comparison with most extremophiles whose survival depends on an environmental factor, such as fish " ice "of the family Channichthyidae that only inhabit the Antarctic ocean where the temperature is zero degrees (O'Brien and Muller, 2010). However, most extremophile organisms are prokaryotes (Gerday and Glansdorff, 2007).
Distribution of extremophile organisms according to the limiting conditions of survival. There are, for example, organisms that survive in extreme pH conditions; lower panel, modified by Rothschild and Mancinelli (2001).
Extreme environments include those characterized by a low or high temperature, with excessive values of alkalinity and acidity or with values far from atmospheric pressures; Extreme environments are also considered those that have high salinity concentrations, xenobiotics such as heavy metals, or that lack oxygen. The extremophile prokaryotes have been classified according to the extreme condition of the environment where they live, in seven families:
- Thermophiles, adapted to temperatures that exceed 60ºC.
- Psychophiles, in environments where the temperature is less than zero degrees.
- Halophiles, survive in 1 to 10 times the concentration of salt in the sea.
- Alkalophiles, in environments where the pH is greater than 10.
- Acidophiles, grow in media where the pH value is close to zero.
- Metalophiles, in environments with high concentrations of heavy metals.
- Barophiles, at a hydrostatic pressure greater than 1000 atmospheres (underwater trenches).
Although D. hansenii is not a halophilic yeast, because it can survive without the presence of sodium in the medium, it is an extreme organism-tolerant to sodium, because it supports high concentrations like a strict halophilic; in fact, it is a double attractant organism due to its ability to modulate the expression of its genome in the presence and absence of sodium in the medium.
Gerday C., and Glansdorff N. (2007). Physiology and Biochemistry of Extremophiles. American Society for Microbiology Editor; 472 pp.
O'Brien KM and Mueller IA. (2010). The Unique Mitochondrial Form and Function of Antartic Channichtyid Icefishes. Integrative and Comparative Biology; 50 (6): 993-1008.
Richter K, Haslbeck M and Buchner J. (2010). The heat shock response: life on the verge of death. Mol Cell 40 (2): 253-266.
Irrigation with commercial bottled water increases generation of reactive oxygen species in Nicotiana tabacum
Marissa Calderón-Torres, Edith López-Estrada, Ana E. Ortiz-Reyes1 & Miguel Murguía-Romero
The consumption of commercial bottled water has increased worldwide in a surprising way. To ensure that its consumption does not have harmful effects on human health, research must be carried out. The growth of Nicotiana tabacum plants was analyzed after being irrigated with tap water and commercial bottled. Plants irrigated with commercial bottled water had fewer leaves, some with chlorosis, and had shorter stem and leaf length compared to plants irrigated with tap water, and their root, stem and leaf showed an increase. in the production of reactive oxygen species and a significant decrease in chlorophylls. The chemical analysis of the commercial bottled water showed a low ion concentration and an acidic pH value (5.5) below the minimum of the Mexican standard NOM-127-SSA1-2000 (6.5–8.5). The growth, chlorophyll concentration and antioxidant capacity of plants irrigated with bottled water are negatively affected compared to those irrigated with tap water.
Way to cite
Calderón-Torres M, López-Estrada E, Ortiz-Reyes AE & Murguía-Romero M. 2020. Irrigation with commercial bottled water increases generation of reactive oxygen species in Nicotiana tabacum. Environmental Pollutants and Bioavailability 32:1, 175-186.