Functional diversity of the mechanism of winter photoinhibition across the Plant Kingdom

261 p.Muchos organismos vegetales tienen que enfrentarse a las duras condiciones invernales, sobreviviendo a la combinación de bajas temperaturas y alta irradiación. Para evitar daños en el aparato fotosintético, deben presentar sistemas antioxidantes, así cómo procesos que disipen el exceso lumínico. Entre estos destaca la disipación térmica que consiste en la reemisión del exceso lumínico que llega a la superficie de la planta en forma de calor. Un aumento en la disipación térmica conlleva una disminución de la eficiencia fotosintética. Este proceso es conocido como fotoinhibición, en invierno, más concretamente se la denomina fotoinhibición invernal (WPI). Hasta ahora, la WPI ha sido caracterizada principalmente en leñosas y en algunos cultivos, pero poco se sabe de lo que ocurre en otras especies que también viven de forma natural en zonas con condiciones invernales extremas como son algunas herbáceas, helechos, líquenes, briófitos y algas terrestres. Por ello, en esta tesis, el objetivo principal ha sido conocer la extensión adaptativa de la WPI en el Reino Vegetal. Los principales resultados muestran que: (i) aunque las leñosas son las que presentan valores de WPI más elevados, éste no es un proceso exclusivo de este grupo funcional; (ii) el umbral térmico al que se activa la WPI es 0ºC; (iii) antioxidantes como la zeaxantina son acumulados en innumerables especies durante el invierno, independientemente de su grado de fotoinhibición; (iv) los patrones de fotoinhibición de los tallos son muy parecidos a los de las hojas; (v) en general, las algas de vida libre presentan una WPI mayor que los líquenes; (vi) el efecto positivo que tiene la simbiosis liquénica, va más allá de un simple sombreamiento por parte del hongo al alga; (vii) los cambios en las proteínas tilacoidales durante el invierno no siguen un patrón común en todas las especies estudias. El estudio de la WPI es de gran relevancia, para conocer el comportamiento de ciertas especies bajo las condiciones de cambios climático del planeta

Unraveling the Photoprotective Response of Lichenized and Free-Living Green Algae (Trebouxiophyceae, Chlorophyta) to Photochilling Stress

Lichens and free-living terrestrial algae are widespread across many habitats and develop successfully in ecosystems where a cold winter limits survival. With the goal of comparing photoprotective responses in free-living and lichenized algae, the physiological responses to chilling and photochilling conditions were studied in three lichens and their isolated algal photobionts together as well as in a fourth free-living algal species. We specifically addressed the following questions: (i) Are there general patterns of acclimation in green algae under chilling and photochilling stresses? (ii) Do free-living algae exhibit a similar pattern of responses as their lichenized counterparts? (iii) Are these responses influenced by the selection pressure of environmental conditions or by the phylogenetic position of each species? To answer these questions, photosynthetic fluorescence measurements as well as pigment and low molecular weight carbohydrate pool analyses were performed under controlled laboratory conditions. In general, photochemical efficiency in all free-living algae decreased with increasing duration of the stress, while the majority of lichens maintained an unchanged photochemical activity. Nevertheless, these patterns cannot be generalized because the alga Trebouxia arboricola and the lichen Ramalina pollinaria (associated with Trebouxia photobionts) both showed a similar decrease in photochemical efficiency. In contrast, in the couple Elliptochloris bilobata-Baeomyces rufus, only the algal partner exhibited a broad physiological performance under stress. This study also highlights the importance of the xanthophyll cycle in response to the studied lichens and algae to photochilling stress, while the accumulation of sugars was not related to cold acclimation, except in the alga E. bilobata. The differences in response patterns detected among species can be mainly explained by their geographic origin, although the phylogenetic position should also be considered, especially in some species.FM received a fellowship for PhD students (2012-2015) from the Government of the Basque Country as well as a mobility grant which allowed the collaboration between University of Basque Country (UPV/EHU) and University of Rostock. LG thanks the Deutsche Forschungsgemeinschaft for financial support (DFG GU 1278/1-1). The work was also supported by the project BFU 2010-15021 and CTM2014-53902-C2-2-P from the MINECO and the European Regional Development Fund ERDF (FEDER), and by the Basque Government (UPV/EHU-GV IT-624-13 and UPV/EHU-GV IT-1018-16)

Diversity of winter photoinhibitory responses: a case study in co-occurring lichens, mosses, herbs and woody plants from subalpine environments

Winter evergreens living in mountainous areas have to withstand a harsh combination of high light levels and low temperatures in wintertime. In response, evergreens can activate a photoprotective process that consists of the downregulation of photosynthetic efficiency, referred to as winter photoinhibition (WPI). WPI has been studied mainly in woody evergreens and crops even when, in many instances, other functional groups such as lichens or bryophytes dominate in alpine and boreal habitats. Thus, we aimed to (1) assess the occurrence of WPI within overwintering evergreens comprising woody species, herbs, mosses and lichens, (2) compare the recovery kinetics among those groups and (3) clarify the role of thylakoid proteins and pigments in both processes: WPI and recovery. With this aim, WPI was analyzed in 50 species in the field and recovery kineticcs were studied in one model species from each functional group. Results showed that high levels of WPI are much more frequent among woody plants than in any other group, but are also present in some herbs, lichens and mosses. Winter conditions almost always led to the de‐epoxidation of the xanthophyll cycle. Nevertheless, changes in the de‐epoxidation level were not associated with the activation/deactivation of WPI in the field and did not match changes in photochemical efficiency during recovery treatments. Seasonal changes in thylakoid proteins [mainly D1 (photosystem II core complex protein) and PsbS (essential protein for thermal dissipation)] were dependent on the functional group. The results highlight the diversity of physiological solutions and suggest a physical–mechanical reason for the more conservative strategy of woody species compared with other groups.Marie Curie IEF grant (328370 MELISSA) from the Euro- pean FP7-PEOPLE and a ‘Juan de la Cierva Incorporación’ grant (IJCI-2014-22489) from the Spanish Ministry of Econ- omy and Competitiveness (MINECO) and the European Regional Development Fund ERDF (FEDER). The work was also supported by the project BFU 2010 – 15021 and CTM2014-53902-C2-2-P from the MINECO and the ERDF (FEDER), and by the Basque Government (UPV/EHU-GV IT-624–13 and UPV/EHU-GV IT-1018-16

Photoprotective Strategies of Mediterranean Plants in Relation to Morphological Traits and Natural Environmental Pressure: A Meta-Analytical Approach

Despite being a small geographic extension, Mediterranean Basin is characterized by an exceptional plant biodiversity. Adaptive responses of this biocoenosis are delineated by an unusual temporal dissociation along the year between optimal temperature for growth and water availability. This fact generates the combination of two environmental stress factors: a period of summer drought, variable in length and intensity, and the occurrence of mild to cold winters. Both abiotic factors, trigger the generation of (photo) oxidative stress and plants orchestrate an arsenal of structural, physiological, biochemical, and molecular mechanisms to withstand such environmental injuries. In the last two decades an important effort has been made to characterize the adaptive morphological and ecophysiological traits behind plant survival strategies with an eye to predict how they will respond to future climatic changes. In the present work, we have compiled data from 89 studies following a meta-analytical approach with the aim of assessing the composition and plasticity of photosynthetic pigments and low-molecular-weight antioxidants (tocopherols, glutathione, and ascorbic acid) of wild Mediterranean plant species. The influence of internal plant and leaf factors on such composition together with the stress responsiveness, were also analyzed. This approach enabled to obtain data from 73 species of the Mediterranean flora, with the genus Quercus being the most frequently studied. Main highlights of present analysis are: (i) sort of photoprotective mechanisms do not differ between Mediterranean plants and other floras but they show higher plasticity indexes; (ii) a-tocopherol among the antioxidants and violaxanthin-cycle pigments show the highest responsiveness to environmental factors; (iii) both winter and drought stresses induce overnight retention of de-epoxidised violaxanthin-cycle pigments; (iv) this retention correlates with depressions of Fv/Fm; and (v) contrary to what could be expected, mature leaves showed higher accumulation of hydrophilic antioxidants than young leaves, and sclerophyllous leaves higher biochemical photoprotective demand than membranous leaves. In a global climatic change scenario,the plasticity of their photoprotective mechanisms will likely benefit Mediterranean species against oceanic ones. Nevertheless, deep research of ecoregions other than the Mediterranean Basin will be needed to fully understand photoprotection strategies of this extremely biodiverse floristic biome: the Mediterranean ecosystem.This work was supported by the Basque Government (UPV/EHU-GV IT-1018-16) and by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the ERDF (FEDER) (CTM2014-53902-C2-2-P). RE and BF received a "Juan de la Cierva-Incorporacion" grant (IJCI-2014-21452 and IJCI-2014-22489, respectively). FM received a postdoctoral grant for Recent Ph.D. and MG is recipient of a specialization fellowship for Ph.D. researchers, both awarded by the Research Vice-Rectorate of the UPV/EHU

Seed Carotenoid and Tocochromanol Composition of Wild Fabaceae Species Is Shaped by Phylogeny and Ecological Factors

Carotenoids distribution and function in seeds have been very scarcely studied, notwithstanding their pivotal roles in plants that include photosynthesis and phytohormone synthesis, pigmentation, membrane stabilization and antioxidant activity. Their relationship with tocochromanols, whose critical role in maintaining seed viability has already been evidenced, and with chlorophylls, whose retention in mature seed is thought to have negative effects on storability, remain also unexplored. Here, we aimed at elucidating seed carotenoids relationship with tocochromanols and chlorophylls with regard to phylogenetic and ecological traits and at understanding their changes during germination. The composition and distribution of carotenoids were investigated in seeds of a wide range of wild species across the Fabaceae (the second-most economically important family after the Poaceae). Photosynthetic pigments and tocochromanols were analyzed by HPLC in mature dry seeds of 50 species representative of 5 subfamilies within the Fabaceae (including taxa that represent all continents, biomes and life forms within the family) and at key timepoints during seedling establishment in three species representative of distinct clades. Total-carotenoids content positively correlated with tocopherols in the basal subfamilies Detarioideae, Cercidoideae, and Dialioideae, and with chlorophylls in the Papilionoideae. Papilionoideae lacked tocotrienols and had the highest total-carotenoids, chlorophyll and gamma-tocopherol contents. Interestingly, lutein epoxide was present in 72% of the species including several herbs from different subfamilies. Overall, species original from temperate biomes presented higher carotenoids and lower tocochromanols levels than those from tropical biomes. Also shrub species showed higher carotenoids content than herbs and trees. During germination, total content of photosynthetic pigments increased in parallel to changes in relative abundance of carotenoids: zeaxanthin and anteraxanthin decreased and beta-carotene augmented. Notably, the highest contents of nutritionally valuable carotenoids were found in Papilionoideae subfamily to which all pulses of socio-economic importance belong. The major differences in carotenoids and tocochromanols composition across the Fabaceae are apparently related to phylogeny in conjunction with ecological traits such as biome and growth form.This work was supported by the Basque Government [UPV/EHU-GV IT-1018-16], and by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Research and Development Foundation (FEDER) through (i) [CTM2014-53902-C2-2-P] national grant and (ii) a "Juan de la Cierva-Incorporacion" postdoctoral grant [IJCI-2014-22489] to BF-M. BF-M, FM, and LM-F received a postdoctoral fellowship from the Research Vice Rectorate (UPV/EHU). The Royal Botanic Gardens, Kew, received grant-in-aid from DEFRA

Mycorrhizal-assisted phytoremediation and intercropping strategies improved the health of contaminated soil in a peri-urban area

[EN] Soils of abandoned and vacant lands in the periphery of cities are frequently subjected to illegal dumping and can undergo degradation processes such as depletion of organic matter and nutrients, reduced biodiversity, and the presence of contaminants, which may exert an intense abiotic stress on biological communities. Mycorrhizalassisted phytoremediation and intercropping strategies are highly suitable options for remediation of these sites. A two-year field experiment was conducted at a periurban site contaminated with petroleum hydrocarbons and polychlorinated biphenyls, to assess the effects of plant growth (spontaneous plant species, Medicago sativa, and Populus canadensis, alone vs. intercropped) and inoculation of a commercial arbuscular mycorrhizal and ectomycorrhizal inoculum. Contaminant degradation, plant performance, and biodiversity, as well as a variety of microbial indicators of soil health (microbial biomass, activity, and diversity parameters) were determined. The rhizosphere bacterial and fungal microbiomes were assessed by measuring the structural diversity and composition via amplicon sequencing. Establishment of spontaneous vegetation led to greater plant and soil microbial diversity. Intercropping enhanced the activity of soil enzymes involved in nutrient cycling. The mycorrhizal treatment was a key contributor to the establishment of intercropping with poplar and alfalfa. Inoculated and poplar-alfalfa intercropped soils had a higher microbial abundance than soils colonized by spontaneous vegetation. Our study provided evidence of the potential of mycorrhizal-assisted phytoremediation and intercropping strategies to improve soil health in degraded peri-urban areas.This study was supported by the PhytoSUDOE (SOE1/P5/E0189) and Phy2SUDOE (SOE4/P5/E1021) projects funded by the Interreg Sudoe Programme through the European Regional Development Fund (ERDF), PRADA project (PID2019- 110055RB-C21 and PID2019-110055RB-C22) from MINECO, and the Consolidated Research Group of the Basque Government (GV ITO18-16)

Functional diversity of the mechanism of winter photoinhibition across the Plant Kingdom

261 p.Muchos organismos vegetales tienen que enfrentarse a las duras condiciones invernales, sobreviviendo a la combinación de bajas temperaturas y alta irradiación. Para evitar daños en el aparato fotosintético, deben presentar sistemas antioxidantes, así cómo procesos que disipen el exceso lumínico. Entre estos destaca la disipación térmica que consiste en la reemisión del exceso lumínico que llega a la superficie de la planta en forma de calor. Un aumento en la disipación térmica conlleva una disminución de la eficiencia fotosintética. Este proceso es conocido como fotoinhibición, en invierno, más concretamente se la denomina fotoinhibición invernal (WPI). Hasta ahora, la WPI ha sido caracterizada principalmente en leñosas y en algunos cultivos, pero poco se sabe de lo que ocurre en otras especies que también viven de forma natural en zonas con condiciones invernales extremas como son algunas herbáceas, helechos, líquenes, briófitos y algas terrestres. Por ello, en esta tesis, el objetivo principal ha sido conocer la extensión adaptativa de la WPI en el Reino Vegetal. Los principales resultados muestran que: (i) aunque las leñosas son las que presentan valores de WPI más elevados, éste no es un proceso exclusivo de este grupo funcional; (ii) el umbral térmico al que se activa la WPI es 0ºC; (iii) antioxidantes como la zeaxantina son acumulados en innumerables especies durante el invierno, independientemente de su grado de fotoinhibición; (iv) los patrones de fotoinhibición de los tallos son muy parecidos a los de las hojas; (v) en general, las algas de vida libre presentan una WPI mayor que los líquenes; (vi) el efecto positivo que tiene la simbiosis liquénica, va más allá de un simple sombreamiento por parte del hongo al alga; (vii) los cambios en las proteínas tilacoidales durante el invierno no siguen un patrón común en todas las especies estudias. El estudio de la WPI es de gran relevancia, para conocer el comportamiento de ciertas especies bajo las condiciones de cambios climático del planeta