UV-C tolerance of symbiotic Trebouxia sp. in the space-tested lichen species Rhizocarpon geographicum and Circinaria gyrosa : role of the hydration state and cortex/screening substances

作者：F. J. Sánchez, Joachim Meeßen, M. A. Ruiz, Leopoldo G. Sancho, S. Ott, Carlos Vı́lchez, G. Horneck, Andres Sadowsky, Rosa de la Torre · 发表于：International Journal of Astrobiology · 年份：2013 · DOI：10.1017/s147355041300027x · 被引用次数：38 · 研究领域：Lichen and fungal ecology、Biocrusts and Microbial Ecology、Polar Research and Ecology

Abstract Many experiments were carried out in order to evaluate the survival capacity of extremotolerant lichens when facing harsh conditions, including those of outer space or of simulated Martian environment. For further progress, a deeper study on the physiological mechanisms is needed that confer the unexpected levels of resistance detected on these symbiotic organisms. In this work, the response of the lichenized green algae Trebouxia sp. (a predominant lichen photobiont) to increasing doses of UV-C radiation is studied. UV-C (one of the most lethal factors to be found in space together with vacuum and cosmic-ionizing radiation with high atomic number and energy (HZE) particles) has been applied in the present experiments up to a maximum dose analogue to 67 days in Low Earth Orbit (LEO). For that purpose we selected two extremotolerant and space-tested lichen species in which Trebouxia sp. is the photosynthetic partner: the crustose lichen Rhizocarpon geographicum and the fruticose lichen Circinaria gyrosa. In order to evaluate the effect of the physiological state of the lichen thallus (active when wet and dormant when dry) and of protective structures (cortex and photoprotective pigments) on the resistance of the photobiont to UV-C, four different experimental conditions were tested: (1) dry intact samples, (2) wet intact samples, (3) dry samples without cortex/acetone-rinsed and (4) wet samples without cortex/acetone-rinsed. After irradiation and a 72 hours period of ...