Search results for "ichen"
showing 10 items of 338 documents
The organic air pollutant cumene hydroperoxide interferes with NOantioxidant role in rehydrating lichen
2013
Organic pollutants effects on lichens have not been addressed. Rehydration is critical for lichens, a burst of free radicals involving NO occurs. Repeated dehydrations with organic pollutants could increase oxidative damage. Our aim is to learn the effects of cumene hydroperoxide (CP) during lichen rehydration using Ramalina farinacea (L.) Ach., its photobiont Trebouxia spp. and Asterochloris erici. Confocal imaging shows intracellular ROS and NO production within myco and phycobionts, being the chloroplast the main source of free radicals. CP increases ROS, NO and lipid peroxidation and reduces chlorophyll autofluorescence, although photosynthesis remains unaffected. Concomitant NO inhibit…
Different strategies to achieve Pb-tolerance by the two Trebouxia algae coexisting in the lichen Ramalina farinacea.
2012
Lichen thalli are permeable to airborne substances, including heavy metals, which are harmful to cell metabolism. Ramalina farinacea shows a moderate tolerance to Pb. This lichen comprises two Trebouxia phycobionts, provisionally referred to as TR1 and TR9, with distinct physiological responses to acute oxidative stress. Thus, there is a more severe decay in photosynthesis and photosynthetic pigments in TR1 than in TR9. Similarly, under oxidative stress, antioxidant enzymes and HSP70 protein decrease in TR1 but increase in TR9. Since Pb toxicity is associated with increased ROS formation, we hypothesized greater Pb tolerance in this phycobiont. Accordingly, the aim of the present study was …
The genetic structure of the cosmopolitan three-partner lichenRamalina farinaceaevidences the concerted diversification of symbionts
2012
The epiphytic lichen Ramalina farinacea is distributed throughout the northern hemisphere in which the same two algal Trebouxia species (provisionally named TR1 and TR9) coexist in every thallus. Ramalina farinacea symbionts were characterized based on the two fungal nuclear loci (nrITS and rpb2 ) along with the primary and secondary structures of nrITS from each Trebouxia species in the Iberian Peninsula and Canary Islands. The results indicated a noticeable genetic differentiation between mycobionts from these two geographic areas and also suggested concerted changes in the three partners of a lichen symbiosis toward two clearly distinguishable ‘holobiont’ lineages. Modeling of ITS2 RNA s…
Differences in the cell walls and extracellular polymers of the two Trebouxia microalgae coexisting in the lichen Ramalina farinacea are consistent w…
2015
Trebouxia TR1 and T. TR9 are the two microalgae that coexist within Ramalina farinacea thalli. In the presence of Pb, TR9 formed extracellular aggregates, while TR1 showed a lower wall lead retention capability. Herein, we studied the cell walls and extracellular polymers (EPS) of TR1 and TR9, and their possible implication in the different Pb retention capacity of these microalgae. The proportion of cell walls on the overall cell biomass was 2.6 times higher in TR9 than in TR1. Glycosyl linkage analysis indicated the presence of hot-water soluble β-galactofuranan(s) in both cell walls, distinct from that previously described in Asterochloris, with increased rhamnose content in TR9 and a hi…
Photosynthesis in Lichen: Light Reactions and Protective Mechanisms
2012
Lichens are symbiotic associations (holobionts) established between fungi (mycobionts) and certain groups of cyanobacteria or unicellular green algae (photobionts). This symbiotic association has been essential in establishing the colonization of terrestrial and consequently dry habitats. About 44 genera of algae and cyanobacteria have been reported as lichen photobionts. Due to the uncertain taxonomy of many of these photobionts, these numbers were considered as approximations only. Ahmadjian (1993) estimates that only 25 genera were typical lichen photobionts. The most common cyanobionts are Nostoc, Scytonema, Stigonema, Gloeocapsa, and Calothrix, in order of frequency (Budel, 1992). Gree…
Chloroplast morphology and pyrenoid ultrastructural analyses reappraise the diversity of the lichen phycobiont genus Trebouxia (Chlorophyta)
2022
Abstract Trebouxiophyceae is a wide class of green algae comprising coccoid and elliptic unicells, filaments, blades and colony-forming species that occur in diverse terrestrial and aquatic environments. Within this class, the genus Trebouxia Puymaly is among the most widespread lichen phycobionts worldwide. However, the 29 formally described species based on the combination of morphological traits and genetic diversity woefully underrepresented the overall species-level diversity recognized in the genus. In Trebouxia, reliable differentiation and characterization of the species-level lineages can be achieved by studying the diversity of key diagnostic features of pyrenoid ultrastructure an…
Preliminary assessment of terrestrial microalgae isolated from lichens as testing species for environmental monitoring: Lichen phycobionts present hi…
2013
Bioassays constitute a tool for pollution analysis providing a holistic approach and high-quality indication of the toxicity. Microbioassays allow evaluating the toxicity of many samples, implying lower costs and enabling routine monitoring and pollution control. But tests conducted so far are limited to the use of a small number of taxa. Lichens are excellent bioindicators of pollution with great ecological significance. Studies show that the phycobiont is more sensitive to pollutants than the mycobiont. Phycobiont have features such as adaptation to anhydrobiosis and relatively rapid growth in vitro, making them suitable for microbioassays. Our aim is to determine the sensitivity of phyco…
Two Trebouxia algae with different physiological performances are ever-present in lichen thalli of Ramalina farinacea. Coexistence versus Competition?
2010
This study was funded by the Spanish Ministry of Education and Science (CGL2006-12917-C02-01/02), the Spanish Ministry of Science and Innovation (CGL2009-13429-C02-01/02), the AECID (PCI_A/024755/09) and the Generalitat Valenciana (PROMETEO 174/2008 GVA). We are grateful to Dr J. Gimeno-Romeu (University of California, Davis, USA) and to Dr P. J. G. de Nova (IREC, Ciudad Real, Spain), who were the first to isolate DNA from Ramalina farinacea thalli in our group. Wendy Ran revised the manuscript in English.
The Lichen Genus Usnea On Quercus Suber In Iberian Cork-Oak Forests
2017
AbstractFifteen species of Usnea are recorded from Iberian cork-oak forests: U. ceratina, U. comma, U. dasaea, U. esperantiana, U. flammea, U. fulvoreagens, U. glabrata, U. hirta, U. mutabilis, U. rubicunda, U. subcornuta, U. subfloridana U. subscabrosa, U. substerilis and U. wasmuthii. A key for these species is provided. Details of morphology, chemistry, distribution, ecology and taxonomy are discussed. Usnea dasaea is reported as new to the Iberian Peninsula. New chemotypes of U. fulvoreagens (with squamatic acid) and U. wasmuthii (with psoromic acid) have been identified. Distribution maps of U. dasaeaand U. subcornuta in Europe are presented. A new combination, Usnea subfloridana subsp…
International Vocational Education and Training Research: An Introduction to the Special Issue
2021
The seven articles in this special issue represent a wide range of international comparative and review studies by international research teams from China, Germany, India, Russia, Switzerland and Mexico. The presented projects are part of the national program "Research on the Internationalisation of Vocational Education and Training", funded by the German Federal Ministry of Education and Research (BMBF). An adapted version of Urie Bronfenbrenner���s ecological systems theory forms the conceptual framework of the special issue. The four system levels (micro, meso, exo and macro) are addressed by one article each. The article on the microsystem level focuses on the intended and implemented c…