First and second line mechanisms of cadmium detoxification in the lichen photobiont Trebouxia impressa (Chlorophyta)

• Published in: Environmental pollution (1987) 2008, Vol.151 (2), p.280-286
• Main Authors: Sanità di Toppi, L., Pawlik-Skowrońska, B., Vurro, E., Vattuone, Z., Kalinowska, R., Restivo, F.M., Musetti, R., Skowroński, T.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Antioxidants - metabolism; Applied ecology; biochemical mechanisms; Biological and medical sciences; biological resistance; Cadmium; Cadmium - pharmacokinetics; cell culture; chlorophyll; Chlorophyta - chemistry; Chlorophyta - metabolism; Chlorophyta - ultrastructure; Ecotoxicology, biological effects of pollution; Environmental Pollutants - pharmacokinetics; Fundamental and applied biological sciences. Psychology; General aspects; glutathione; Glutathione - analysis; Glutathione - metabolism; Heat-Shock Proteins - metabolism; heavy metals; Inactivation, Metabolic; Lichenes; Lichens; Lichens - metabolism; metabolic detoxification; metal tolerance; microalgae; Microscopy, Electron, Transmission; Oxidative Stress; photobionts; Physcia adscendens; Phytochelatins; Phytochelatins - metabolism; Plant cytology, morphology, systematics, chorology and evolution; plant proteins; plant stress; protective effect; Stress proteins; symbionts; symbiosis; synergism; synergists; Thallophyta; Time; toxic substances; transmission electron microscopy; Trebouxia; Trebouxia impressa
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2007.06.010

“First line” defence mechanisms, such as phytochelatin biosynthesis, and “second line” mechanisms, such as stress protein induction, were investigated in cadmium-exposed cells of Trebouxia impressa Ahmadjian, a green microalgal species that is a common photobiont of the lichen Physcia adscendens (Fr.) H. Olivier. When T. impressa cells were exposed to 0, 9 and 18 μM Cd for 6, 18 and 48 h, glutathione and phytochelatins efficiently protected the cells against Cd damage. By contrast, the highest Cd concentration (36 μM) at the longest exposure-time (48 h) caused marked drops in glutathione and phytochelatin content, several types of ultrastructural damage, and decreases in cell density and total chlorophyll concentration. In this case, induction of stress proteins was observed, but only long after the induction of phytochelatins. Thus, stress proteins could represent a “second line” mechanism to counteract Cd stress, activated when there is a decline in the “first line” mechanism of Cd detoxification given by phytochelatins. Trebouxia impressa photobionts protect themselves against cadmium stress by means of phytochelatins and stress proteins.