Browsing by Author "Salinas, Paula"

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    Glutaredoxin GRXS13 plays a key role in protection against photooxidative stress in Arabidopsis
    (OXFORD UNIV PRESS, 2012) Laporte, Daniel; Olate, Ema; Salinas, Paula; Salazar, Marcela; Jordana, Xavier; Holuigue, Loreto
    Glutaredoxins (GRXs) belong to the antioxidant and signalling network involved in the cellular response to oxidative stress in bacterial and eukaryotic cells. In spite of the high number of GRX genes in plant genomes, the biological functions and physiological roles of most of them remain unknown. Here the functional characterization of the Arabidopsis GRXS13 gene (At1g03850), that codes for two CC-type GRX isoforms, is reported. The transcript variant coding for the GRXS13.2 isoform is predominantly expressed under basal conditions and is the isoform that is induced by photooxidative stress. Transgenic lines where the GRXS13 gene has been knocked down show increased basal levels of superoxide radicals and reduced plant growth. These lines also display reduced tolerance to methyl viologen (MeV) and high light (HL) treatments, both conditions of photooxidative stress characterized by increased production of superoxide ions. Consistently, lines overexpressing the GRXS13.2 variant show reduced MeV- and HL-induced damage. Alterations in GRXS13 expression also affect superoxide levels and the ascorbate/dehydroascorbate ratio after HL-induced stress. These results indicate that GRXS13 gene expression is critical for limiting basal and photooxidative stress-induced reactive oxygen species (ROS) production. Together, these results place GRXS13.2 as a member of the ROS-scavenging/antioxidant network that shows a particularly low functional redundancy in the Arabidopsis GRX family.
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    TGA class II transcription factors are essential to restrict oxidative stress in response to UV-B stress in Arabidopsis
    (2021) Herrera Vásquez, Ariel Esteban; Fonseca Cárdenas, Alejandro Alfredo; Ugalde Valdivia, José Manuel; Lamig Giannini, Liliana Andrea; Seguel Avello, Aldo Luis; Moyano Yugovic, Tomás Custodio; Gutiérrez Ilabaca, Rodrigo Antonio; Salinas, Paula; Vidal, Elena A.; Holuigue Barros, Loreto
    Plants possess a robust metabolic network for sensing and controlling reactive oxygen species (ROS) levels upon stress conditions. Evidence shown here supports a role for TGA class II transcription factors as critical regulators of genes controlling ROS levels in the tolerance response to UV-B stress in Arabidopsis. First, tga256 mutant plants showed reduced capacity to scavenge H2O2 and restrict oxidative damage in response to UV-B, and also to methylviologen-induced photooxidative stress. The TGA2 transgene (tga256/TGA2 plants) complemented these phenotypes. Second, RNAseq followed by clustering and Gene Ontology term analyses indicate that TGA2/5/6 positively control the UV-B-induced expression of a group of genes with oxidoreductase, glutathione transferase, and glucosyltransferase activities, such as members of the glutathione S-transferase Tau subfamily (GSTU), which encodes peroxide-scavenging enzymes. Accordingly, increased glutathione peroxidase activity triggered by UV-B was impaired in tga256 mutants. Third, the function of TGA2/5/6 as transcriptional activators of GSTU genes in the UV-B response was confirmed for GSTU7, GSTU8, and GSTU25, using quantitative reverse transcription–PCR and ChIP analyses. Fourth, expression of the GSTU7 transgene complemented the UV-B-susceptible phenotype of tga256 mutant plants. Together, this evidence indicates that TGA2/5/6 factors are key regulators of the antioxidant/detoxifying response to an abiotic stress such as UV-B light overexposure.
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    Transcription factor TGA2 is essential for UV-B stress tolerance controlling oxidative stress in Arabidopsis
    (2020) Herrera Vásquez, Ariel Esteban; Fonseca Cárdenas, Alejandro Alfredo; Ugalde Valdivia, José Manuel; Lamig Giannini, Liliana Andrea; Seguel Avello, Aldo Luis; Moyano Yugovic, Tomás Custodio; Gutiérrez Ilabaca, Rodrigo Antonio; Salinas, Paula; Vidal, Elena A.; Holuigue Barros, Loreto
    Plants possess a diversity of Reactive Oxygen Species (ROS)-processing enzymes involved in sensing and controlling ROS levels under basal and stressful conditions. There is little information on the transcriptional regulators that control the expression of these ROS-processing enzymes, particularly at the onset of the defense response to abiotic stress. Filling this gap, this paper reports a critical role for Arabidopsis TGA class II factors (TGA2, TGA5, and TGA6) in the tolerance response to UV-B light and photooxidative stress, by activating the expression of genes with antioxidative roles. We identified two clusters of genes responsive to UV-B and activated by TGA2/5/6 were identified using RNAseq and clustering analysis. The GSTU gene family, which encodes glutathione transferase enzymes from the Tau subclass, was overrepresented in these clusters. We corroborated the TGA2-mediated activation in response to UV-B for three model genes (GSTU7, GSTU8, and GSTU25) using RT-qPCR and ChIP analyses. Interestingly, using tga256 mutant and TGA2- and GSTU7-complemented mutant plants, we demonstrated that TGA2-mediated induction of GSTU genes is essential to control ROS levels and oxidative damage after UV-B and MeV treatments. This evidence positions TGA class II factors, particularly TGA2, as a key players in the redox signaling network of Arabidopsis plants.
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    Transcriptional Control of Glutaredoxin GRXC9 Expression by a Salicylic Acid-Dependent and NPR1-Independent Pathway in Arabidopsis
    (2015) Herrera Vásquez, Ariel Esteban; Carvallo, Loreto; Blanco, Francisca; Tobar, Mariola; Villarroel Candia, Eva; Vicente Carbajosa, Jesús; Salinas, Paula; Holuigue Barros, María Loreto