Message - 7th IAL Symposium
Message - 7th IAL Symposium
Message - 7th IAL Symposium
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Lichen: from genome to ecosystem in a changing world<br />
3I-P<br />
(3I – P8) Submission ID: <strong>IAL</strong>0242-00001<br />
DIFFERENT STRATEGIES TO ACHIEVE Pb-TOLERANCE IN THE TWO TREBOUXIA<br />
PHYCOBIONTS OF THE LICHEN RAMALINA FARINACEA<br />
Casano L.M. 1 , Guera A. 1 , Del Campo E. M. 1 , Barreno E. 2 , Garcia-Breijo F. J. 3 , Alvarez R. 1 , Del Hoyo A. 1 ,<br />
Reig-Armiñana J. 4<br />
1 Plant Biology, University of Alcala, Madrid, Alcala de Henares, Spain<br />
2 Botany, Icbibe, University of Valencia, Valencia, Burjassot, Spain<br />
3 Ecosistemas Agroforestales, Universidad Politecnica de Valencia, Valencia, Valencia, Spain<br />
4 Botany, Icbibe-jardi Botanic , University of Valencia, Valencia, burjassot, Suriname<br />
Ramalina farinacea L. (Ach.) has a relatively high tolerance to Pb (Branquinho et al., 1999). On the<br />
other hand, our group demonstrated that this lichen contains two Trebouxia phycobionts (provisionally named<br />
TR1 and TR9). TR1 and TR9 showed distinct physiological responses to oxidative stress caused by a strong<br />
ROS propagator, which produced a more severe decay in photosynthesis, photosynthetic pigments and proteins<br />
in TR1. Antioxidant enzymes were decreased by oxidative stress in TR1, but increased in TR9. Since Pb toxicity<br />
is caused by enhanced ROS formation, we hypothesized that TR9 phycobiont would be relatively more Pbtolerant<br />
than TR1. Therefore, in the present study we searched for physiological differences between isolated<br />
TR1 and TR9 under Pb exposure by analyzing the extracellular and intracellular Pb accumulation, photosynthetic<br />
pigments and chlorophyll fluorescence parameters. Additionally, the detoxification response to Pb was estimated<br />
by several important antioxidant enzymes: glutathione reductase (GR), superoxide dismutase (SOD), ascorbate<br />
peroxidase (APx) and catalase. As expected, extracellular Pb increased with the augment of Pb in both TR1<br />
and TR9. However, TR9 immobilized significantly more metal than TR1 at extracellular level. The intracellular<br />
Pb uptake followed an opposite trend to that observed for the extracellular Pb, being approximately three times<br />
higher in TR1 than in TR9. However, photosynthetic pigments were not strongly affected by the presence of<br />
Pb within cells in either TR1 or TR9, since it was not observed any pigment decay higher than 10% (respect to<br />
controls). Accordingly, photosynthetic electron transport was not affected by the presence of Pb, as evidence by<br />
absence of PSII photoinhibition and the lack of effect on the ΦPSII in both phycobionts. Control levels of GR,<br />
SOD and APx were significantly higher in TR1 that in TR9. However, Pb induced the three enzymes in TR9 while<br />
it had no effect on TR1, so that antioxidant activities were quantitatively similar in both phycobionts under Pb<br />
treatments. In conclusion, each algal species seem to have acquired similar levels of Pb tolerance through the<br />
integration of distinct morphological, biochemical and physiological features. [MCINN (CGL2009-13429-C02-<br />
01/02), AECID (PCI_A_l024755/09) and Generalitat Valenciana (PROMETEO 174/2008 GVA)]<br />
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