title: The Effect of High-Dose Ionizing Radiation on the Astrobiological Model Lichen Circinaria gyrosa.
abstract: The lichen Circinaria gyrosa is an astrobiological model defined by its high capacity of resistance to space conditions and to a simulated martian environment. Therefore, it became part of the currently operated BIOMEX experiment on board the International Space Station and the recent STARLIFE campaign to study the effects of four types of space-relevant ionizing radiation. The samples were irradiated with helium and iron ions at doses up to 2 kGy, with X-rays at doses up to 5 kGy and with γ rays at doses from 6 to 113 kGy. Results on C. gyrosa's resistance to simulated space ionizing radiation and its post-irradiation viability were obtained by (i) chlorophyll a fluorescence of photosystem II (PSII), (ii) epifluorescence microscopy, (iii) confocal laser scanning microscopy (CLSM), and (iv) field emission scanning electron microscopy (FESEM). Results of photosynthetic activity and epifluorescence show no significant changes up to a dose of 1 kGy (helium ions), 2 kGy (iron ions), 5 kGy (X-rays)-the maximum doses applied for those radiation qualities-as well as a dose of 6 kGy of γ irradiation, which was the lowest dose applied for this low linear energy transfer (LET) radiation. Significant damage in a dose-related manner was observed only at much higher doses of γ irradiation (up to 113 kGy). These data corroborate the findings of the parallel STARLIFE studies on the effects of ionizing radiation on the lichen Circinaria gyrosa, its isolated photobiont, and the lichen Xanthoria elegans. Key Words: Simulated space ionizing radiation-Gamma rays-Extremotolerance-Lichens-Circinaria gyrosa-Photosynthetic activity. Astrobiology 17, 145-153.
authors.affiliation: 1 Departamento de Observación de la Tierra, Instituto Nacional de Técnica Aeroespacial (INTA) , Madrid, Spain .
authors.forename: Rosa
authors.initials: R
authors.lastname: de la Torre
authors.affiliation: 2 Instituto de Recursos Naturales y Agrobiología de Sevilla-CSIC , Sevilla, Spain .
authors.forename: Ana Zélia
authors.initials: AZ
authors.lastname: Miller
authors.affiliation: 2 Instituto de Recursos Naturales y Agrobiología de Sevilla-CSIC , Sevilla, Spain .
authors.forename: Beatriz
authors.initials: B
authors.lastname: Cubero
authors.affiliation: 1 Departamento de Observación de la Tierra, Instituto Nacional de Técnica Aeroespacial (INTA) , Madrid, Spain .
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Martín-Cerezo
authors.affiliation: 3 Radiation Biology Department, Institute of Aerospace Medicine , German Aerospace Center (DLR), Cologne, Germany .
authors.forename: Marina
authors.initials: M
authors.lastname: Raguse
authors.affiliation: 4 Institute of Botany, Heinrich-Heine-University (HHU) , Düsseldorf, Germany .
authors.forename: Joachim
authors.initials: J
authors.lastname: Meeßen
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D004307:Dose-Response Relationship, Radiation; D018559:Exobiology; D008011:Lichens / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010788:Photosynthesis / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D011839:Radiation, Ionizing; D013052:Spectrometry, X-Ray Emission
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D000077194:Chlorophyll A