title: Role of abscisic acid (ABA) in activating antioxidant tolerance responses to desiccation stress in intertidal seaweed species.
abstract: The hormone ABA regulates the oxidative stress state under desiccation in seaweed species; an environmental condition generated during daily tidal changes. Desiccation is one of the most important factors that determine the distribution pattern of intertidal seaweeds. Among most tolerant seaweed is Pyropia orbicularis, which colonizes upper intertidal zones along the Chilean coast. P. orbicularis employs diverse mechanisms of desiccation tolerance (DT) (among others, e.g., antioxidant activation, photoinhibition, and osmo-compatible solute overproduction) such as those used by resurrection plants and bryophytes. In these organisms, the hormone abscisic acid (ABA) plays an important role in regulating responses to water deficit, including gene expression and the activity of antioxidant enzymes. The present study determined the effect of ABA on the activation of antioxidant responses during desiccation in P. orbicularis and in the sensitive species Mazzaella laminarioides and Lessonia spicata. Changes in endogenous free and conjugated ABA, water content during the hydration-desiccation cycle, enzymatic antioxidant activities [ascorbate peroxidase (AP), catalase (CAT) and peroxiredoxine (PRX)], and levels of lipid peroxidation and cell viability were evaluated. The results showed that P. orbicularis had free ABA levels 4-7 times higher than sensitive species, which was overproduced during water deficit. Using two ABA inhibitors (sodium tungstate and ancymidol), ABA was found to regulate the activation of the antioxidant enzymes activities during desiccation. In individuals exposed to exogenous ABA the enzyme activity increased, concomitant with low lipid peroxidation and high cell viability. These results demonstrate the participation of ABA in the regulation of DT in seaweeds, and suggest that regulatory mechanisms with ABA signaling could be of great importance for the adaptation of these organisms to dehydration.
authors.affiliation: Departamento de Ecología y Biodiversidad, Facultad de Ecología y Recursos Naturales, Universidad Andres Bello, República 440, Santiago, Chile.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Guajardo
authors.affiliation: Departamento de Ecología, and Center of Applied Ecology and Sustainability (CAPES), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.|UMI 3614, Evolutionary Biology and Ecology of Algae, Station Biologique de Roscoff, Roscoff, France.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Correa
authors.affiliation: Departamento de Ecología y Biodiversidad, Facultad de Ecología y Recursos Naturales, Universidad Andres Bello, República 440, Santiago, Chile. lorettocontreras@unab.cl.|Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile. lorettocontreras@unab.cl.
authors.forename: Loretto
authors.initials: L
authors.lastname: Contreras-Porcia
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000222:Adaptation, Physiological; D020418:Algal Proteins / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D060387:Ascorbate Peroxidases / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D032181:Craterostigma / Q000166:cytology / Q000502:physiology*; D003890:Desiccation; D015227:Lipid Peroxidation; D018384:Oxidative Stress / Q000187:drug effects; D010937:Plant Growth Regulators / Q000378:metabolism*; D000461:Rhodophyta / Q000166:cytology / Q000502:physiology*; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000378:metabolism; D014867:Water / Q000502:physiology
chemical_list: D020418:Algal Proteins; D000975:Antioxidants; D010937:Plant Growth Regulators; D014867:Water; D000040:Abscisic Acid; D060387:Ascorbate Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase
keywords: Desiccation tolerance; Oxidative stress; Pyropia; Water deficit Seaweeds