Metabolic processes sustaining the reviviscence of lichen Xanthoria elegans (Link) in high mountain environments. Serge Aubert, Christine Juge, Anne-Marie Boisson, Elisabeth Gout, Richard Bligny To cite this version: Serge Aubert, Christine Juge, Anne-Marie Boisson, Elisabeth Gout, Richard Bligny. Metabolic pro- cesses sustaining the reviviscence of lichen Xanthoria elegans (Link) in high mountain environments.. Planta, Springer Verlag, 2007, 226 (5), pp.1287-97. 10.1007/s00425-007-0563-6. hal-00188424 HAL Id: hal-00188424 https://hal.archives-ouvertes.fr/hal-00188424 Submitted on 16 Nov 2007 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Page 1 of 32 Planta 1 2 3 Serge Aubert 1* . Christine Juge 1 . Anne-Marie Boisson2 . Elisabeth Gout2 . Richard Bligny 1,2 4 5 6 7 Metabolic processes sustaining the reviviscence of the lichen Xanthoria elegans (Link) in 8 9 high mountain environment 10 11 12 1 Station Alpine Joseph Fourier , UMS 2925 UJF CNRS, Université Joseph Fourier, BP 53, 38041 13 14 Grenoble cedex 9, France 15 16 17 18 For Peer Review 19 2 Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168, institut de 20 21 Recherche en Technologies et Sciences pour le Vivant, CEA, 17 rue des Martyrs, 38054 22 23 Gren oble cedex 9, France 24 25 26 27 28 * Corresponding author : 29 30 E-mail: serge.aubert@ujf -grenoble.fr 31 32 Fax: + 33 4 76 51 42 79 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1 Planta Page 2 of 32 1 2 3 Abstract 4 5 Adaptation to alternating periods of desiccation and hydration is one of the lichen ’s requirements 6 7 for survival in high mountain enviro nment. In the dehydrated state, respiration and 8 9 photosynthesis of the foliaceous lichen Xanthoria elegans were below the threshold of CO 2- 10 detection by infrared gas analysis. Following hydration, respiration totally recovered within 11 12 seconds and photosynthes is within minutes. In order to identify metabolic processes that may 13 14 contribute to restart so quickly and efficiently lichen physiological activity, we analysed the 15 31 16 metabolite profile of lichen thalli step by step during hydration/dehydration cycle s, using P- 17 and 13 C-NMR . It appeared that the recovery of respiration was anticipated during dehydration by 18 For Peer Review 19 the accumulation of important stores of gluconate 6 -P (glcn -6-P) and by the preservation of the 20 21 nucleotide pools, whereas glyco lysis and photosynthesis in termediates like glucose 6 -P and 22 23 ribulose 1,5-diphosphate disappeared . The important pools of polyols present in both X. elegans 24 25 photo- and mycobiont likely contributed to protect cells constituents like nucleotides, proteins, 26 and membrane lipids, and to p reserve the intactness of intracellular structures during desiccation. 27 28 Our data indicate that glcn -6-P accumulat ed due to the activat ion of the oxidative pentose 29 30 phosphate pathway , in response to cell need for reducing power (NADPH) during the 31 32 dehydration-triggered down regulation of metabolism . On the contrary, glcn -6-P was 33 34 metabolised immediately after hydration, supplying respiration with substrates during the 35 recovery of the pools of glycolysis and photosynthesis intermediate s. Finally , the high net 36 37 photosynthetic activit y of wet X. elegans thalli at low temperature may help this alpine lichen to 38 39 take advantage of short hydration opportunities such as ice melting, thus favouring its growth in 40 41 the harsh high mountain climate . 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 Page 3 of 32 Planta 1 2 3 Keyw ords 4 5 lichens . revivis cence . energy metabolism . metabolic profiling . NMR spectroscopy 6 7 8 9 Abbreviation 10 PCA, perchloric acid ; CDTA, 1,2-cyclohexylenedinitrilotetraacetic acid 11 12 13 14 15 16 17 18 For Peer Review 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Planta Page 4 of 32 1 2 3 Introduction 4 5 6 7 Lichens are living organisms among the most resistant to extreme environments including the 8 9 deserts and frigid areas of the five continents. In the alpine environment, these symbiotic 10 organisms are exposed to harsh fluctuations of water supply , light intensity , and temperature 11 12 (Kappen 1988; Körner, 2003). Th is is typically the case for Xanthoria elegans (Link) used in this 13 14 study, wh ose growth on rocky surfaces mainly depends on atmospheric water input. X. elegans is 15 16 a saxicolous desiccation-tolerant lichen of the Teloschistaceae family (Helms, 2003), contain ing 17 an ascomycetous fungus and a unic ellular green alga belonging to the Teloschistes and 18 For Peer Review 19 Trebouxia genus, respectively (Helms, 2003). In the place w here they were harvested , t halli 20 21 naturally undergo hydration/dehydration cycles, growing when they are hydrated by snow 22 23 melting, rain , or dew . 24 25 Metabolic activity of lichen thalli appreciated via gas exchanges become s almost 26 undetectable when their water content decreases below 10-15% of their dry weight (Lange 1980; 27 28 Schroeter et al. 1991). Nevertheless , lichens may take up sufficient amounts of water from the 29 30 vapour in the atmosphere ( Lange 1980) and thus maintain a significant metabolic activity above 31 32 this rather low hydration threshold . Hydration is facilitated by high concentrations of polyols in 33 34 both photo - and myco bio nt (Rundel 1988) that lo wer water potential (Lange et al. 1990), thus 35 allowing photosynthetic activity even under increasing degrees of desiccation (Nash et al. 1990). 36 37 Immersion in water or rewetting in moist air triggers a process of reviviscence in dry 38 39 desiccation-tolerant lichen s (Smith and Molesworth 1973; Bewley 1979). Respiration and 40 41 photosynthesis shortly resume normal activities upon hydration, indicating that cell damages 42 induced by drying are rapidly repair ed (Farrar and Smith, 1976). Indeed, according to different 43 44 authors (Dudley and Lechowicz 1987; Longton 1988), desiccated membranes are leaky, 45 46 exposing cell contents to surrounding solution during rewetting, which lead s to loss es of organic 47 48 and inorganic solutes . Thus, c ell s urvival requires a rapid reseal ing of plasma membrane 49 disruptions (McNeil and Steinhardt 1997; McNeil et al. 2003). Nevertheless , a delay for repairs 50 51 and synthesi s of lost metabolites could be expected . 52 53 Intense solar radiation is a nother environmental parameter that threatens lichens with the 54 55 poten tial damaging effects of reactive oxygen species (ROS) production (Fridovich, 1999), in 56 57 particular when photosynthetic water oxidation stops due to dehydration. In the plant kingdom, 58 59 60 4 Page 5 of 32 Planta 1 2 3 the ability to withstand light stress and desiccation of vegetative organ s involves various 4 5 mechanisms recently reviewed by Hoekstra et al. (2001), Rascio and La Rocca (2005), and 6 7 Heber et al. (2005) . In hydrated organs, t hese include increased energy dissipation by 8 9 fluorescence at the PSII level and cyclic electron transport a round PSI (Heber and Walker 1992; 10 Manuel et al. 1999; Cornic et al. 2000). On the contrary, when they are dry, poikilohydric 11 12 organisms do not emit light-induced fluorescence, revealing an inactivation of PSII function 13 14 (Lange et al. 1989). These organisms m inimise damage by activating exciton transfer to 15 16 quenchers and convert ing excess energy to heat (Bilger et al. 1989; Heber et al. 2000). 17 Interestingly, following hydration, a burst of intracellular production of ROS was reported in 18 For Peer Review 19 photo - and mycobiont of Ramalina lacera , and t his burst modifies superoxyde dismutase, 20 21 catalase, glutathione reductase, and glucose 6-P dehydrogenase activities (Weissman et al. 2005). 22 23 In desiccation-tolerant plants , the recovery of cell damages upon hydration, and the 24 25 subsequent restoration of cell functions, involves various and complex inductive mechanisms 26 including gene transcriptions and an increased need for protein turnover (Oliver et al. 2004). 27 28 Therefore it requires a rather lengthy time ranging from a few hours to sever al days (Gaff, 1997). 29 30 In contrast , we observed that the respiration and the photosynthetic activity of different high 31 32 mountain lichens restarted almost immediately after rewetting . Therefore, we hypothesised that 33 34 the rapid recovery of these organisms relie s on the preservation/accumulation of key pools of 35 metabolites during dehydration. We supposed, f or example , that intermediates of energy 36 37 metabolism like respiratory substrates, nucleosides, and pyridine nucleotides did not massively 38 39 leak out photo- and my cobiont during hydration/desiccation cycles in lichens. To substantiate 40 41 this hypothesis, we assess ed in parallel the respiration and photosynthe tic activities and the 42 metabolite profile s of X.