Exogenous proline mediates alleviation of cadmium stress by promoting photosynthetic activity, water status and antioxidative enzymes activities of young date palm (Phoenix dactyliferaL.)

International audienceThe ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30mg CdCl2kg(-1) soil) whether supplied or not with exogenous proline (20mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plant

Enzymatic antioxidant responses and mineral status in roots and leaves of olive plants subjected to fluoride stress

International audienceFluoride (F) as one of the most toxic pollutants affecting the environment severely restricted plant growth and development. The Fluoride toxicity was studied in young olive plants (Olea europaea L. cv Chemlali), which were irrigated for 5 months with increasing NaF concentration: 0 (control), 20, 40, and 80 mM NaF. The NaF application resulted in an increase of the F content in plant tissues with a higher level in roots compared to leaves. Olive plants treated with 20 or 40 mM NaF maintained their mineral status and activated their antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase). In fact, lipid peroxidation and electrolyte leakage were not affected in the plant leaves. However, olive plants treated with 80 mM NaF showed (i) the highest reduction of antioxidant enzyme activities and mineral contents, and (ii) an increase of oxidative stress markers such as hydrogen peroxide, thiobarbituric acid reactive substances and electrolyte leakage in both roots and leaves. © 201

Characterization of the responses to saline stress in the symbiotic green microalga Trebouxia sp. TR9

[EN] Main conclusion. For the first time we provide a study on the physiological, ultrastructural and molecular effects of salt stress on a terrestrial symbiotic green microalga, Trebouxia sp. TR9. Although tolerance to saline conditions has been thoroughly studied in plants and, to an extent, free-living microalgae, scientific data regarding salt stress on symbiotic lichen microalgae is scarce to non-existent. Since lichen phycobionts are capable of enduring harsh, restrictive and rapidly changing environments, it is interesting to study the metabolic machinery operating under these extreme conditions. We aim to determine the effects of prolonged exposure to high salt concentrations on the symbiotic phycobiont Trebouxia sp. TR9, isolated from the lichen Ramalina farinacea. Our results suggest that, when this alga is confronted with extreme saline conditions, the cellular structures are affected to an extent, with limited chlorophyll content loss and photosynthetic activity remaining after 72h of exposure to 5M NaCl. Furthermore, this organism displays a rather different molecular response compared to land plants and free-living halophile microalgae, with no noticeable increase in ABA levels and ABA-related gene expression until the external NaCl concentration is raised to 3M NaCl. Despite this, the ABA transduction pathway seems functional, since the ABA-related genes tested are responsive to exogenous ABA. These observations could suggest that this symbiotic green alga may have developed alternative molecular pathways to cope with highly saline environments.Supported by the Ministerio de Economía y Competitividad (MINECO, Spain) and FEDER (CGL2016-79158-P), and the PROMETEO Excellence in Research Program (Generalitat Valenciana, Spain) (PROMETEO/2017/039). Funding for Ernesto Hinojosa-Vidal was also provided by MINECO (BES-2013-065511).Hinojosa-Vidal, E.; Marco, F.; Martínez-Alberola, F.; Escaray, F.; García-Breijo, F.; Reig-Armiñana, J.; Carrasco, P.... (2018). Characterization of the responses to saline stress in the symbiotic green microalga Trebouxia sp. TR9. Planta. 248(6):1473-1486. https://doi.org/10.1007/s00425-018-2993-8S147314862486Álvarez R, del Hoyo A, Díaz-Rodríguez C et al (2015) Lichen rehydration in heavy metal-polluted environments: Pb modulates the oxidative response of both Ramalina farinacea thalli and its isolated microalgae. 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