Element content and expression of genes of interest in guard cells are connected to spatiotemporal variations in stomatal conductance

Element content and expression of genes of interest on single cell types, such as stomata, provide valuable insights into their specific physiology, improving our understanding of leaf gas exchange regulation. We investigated how far differences in stomatal conductance (g(s)) can be ascribed to changes in guard cells functioning in amphistomateous leaves. g(s) was measured during the day on both leaf sides, on well-watered and drought-stressed trees (two Populus euramericana Moench and two Populus nigra L. genotypes). In parallel, guard cells were dissected for element content and gene expressions analyses. Both were strongly arranged according to genotype, and drought had the lowest impact overall. Normalizing the data by genotype highlighted a structure on the basis of leaf sides and time of day both for element content and gene expression. Guard cells magnesium, phosphorus, and chlorine were the most abundant on the abaxial side in the morning, where g(s) was at the highest. In contrast, genes encoding H+-ATPase and aquaporins were usually more abundant in the afternoon, whereas genes encoding Ca2+-vacuolar antiporters, K+ channels, and ABA-related genes were in general more abundant on the adaxial side. Our work highlights the unique physiology of each leaf side and their analogous rhythmicity through the day

Evaluation of simulated biomass damage in forest ecosystems induced by ozone against observation-based estimates

Regional estimates of the effects of ozone pollution on forest growth depend on the availability of reliable damage functions that estimate a representative ecosystem response to ozone exposure. A number of such damage functions for forest tree species and forest functional types have recently been published and subsequently applied in terrestrial biosphere models to estimate regional or global effects of ozone on forest tree productivity and carbon storage in the living plant biomass. The resulting impacts estimated by these biosphere models show large uncertainty in the magnitude of ozone effects predicted. To understand the role that these damage functions play in determining the variability of estimated ozone impacts, we use the O-CN biosphere model to provide a standardised modelling framework. We test four published damage functions describing the leaf-level, photosynthetic response to ozone exposure (targeting Vcmax or net photosynthesis) in terms of their simulated whole-tree biomass responses against field data from 23 ozone filtration/fumigation experiments conducted with European tree species at sites across Europe with a range of climatic conditions. Our results show that none of these previously published damage functions lead to simulated whole-tree biomass reductions in agreement with the observed dose-response relationships derived from these field experiments, and instead lead to significant over- / or underestimations of the ozone effect. By reparameterising these photosynthetic based damage functions we develop linear, plant functional type specific dose-response relationships, which provide accurate simulations of the observed whole-tree biomass response across these 23 experiments

Evaluation of simulated ozone effects in forest ecosystems against biomass damage estimates from fumigation experiments

Regional estimates of the effects of ozone pollution on forest growth depend on the availability of reliable injury functions that estimate a representative ecosystem response to ozone exposure. A number of such injury functions for forest tree species and forest functional types have recently been published and subsequently applied in terrestrial biosphere models to estimate regional or global effects of ozone on forest tree productivity and carbon storage in the living plant biomass. The resulting impacts estimated by these biosphere models show large uncertainty in the magnitude of ozone effects predicted. To understand the role that these injury functions play in determining the variability in estimated ozone impacts, we use the O-CN biosphere model to provide a standardised modelling framework. We test four published injury functions describing the leaf-level, photosynthetic response to ozone exposure (targeting the maximum carboxylation capacity of Rubisco (V$_{cmax}$) or net photosynthesis) in terms of their simulated whole-tree biomass responses against data from 23 ozone filtration/fumigation experiments conducted with young trees from European tree species at sites across Europe with a range of climatic conditions. Our results show that none of these previously published injury functions lead to simulated whole-tree biomass reductions in agreement with the observed dose–response relationships derived from these field experiments and instead lead to significant over- or underestimations of the ozone effect. By re-parameterising these photosynthetically based injury functions, we develop linear, plant-functional-typespecific dose–response relationships, which provide accurate simulations of the observed whole-tree biomass response across these 23 experiments

Genes and gene clusters related to genotype and drought induced variation in saccharification potential, lignin content, and wood anatomical traits in Populus nigra:Saccharification, Wood Anatomy and Gene Clusters

Wood is a renewable resource that can be employed for the production of second generation biofuels by enzymatic saccharification and subsequent fermentation. Knowledge on how the saccharification potential is affected by genotype-related variation of wood traits and drought is scarce. Here, we used three Populus nigra genotypes from habitats differing in water availability to (i) investigate the relationships between wood anatomy, lignin content and saccharification and (ii) identify genes and co-expressed gene clusters related to genotype and drought-induced variation in wood traits and saccharification potential. The three poplar genotypes differed in wood anatomy, lignin content and saccharification potential. Drought resulted in reduced cambial activity, decreased vessel and fibre lumina, and increased the saccharification potential. The saccharification potential was unrelated to lignin content as well as to most wood anatomical traits. RNA sequencing of the developing xylem revealed that 1.5% of the analysed genes were differentially expressed in response to drought, while 67% differed among the genotypes. Weighted gene correlation network analysis identified modules of co-expressed genes correlated with saccharification potential. These modules were enriched in gene ontology terms related to cell wall polysaccharide biosynthesis and modification and vesicle transport, but not to lignin biosynthesis. Among the most strongly saccharification-correlated genes, those with regulatory functions, especially kinases were prominent. We further identified transcription factors whose transcript abundances differed among genotypes, and which were co45 regulated with genes for biosynthesis and modifications of hemicelluloses and pectin. Overall, our study suggests that the regulation of pectin and hemicellulose metabolism is a promising target for improving wood quality of second generation bioenergy crops. The causal relationship of the identified genes and pathways with saccharification potential needs to be validated in further experiments.publishersversionPeer reviewe

Comparative transcriptomics of drought responses in Populus: a meta-analysis of genome-wide expression profiling in mature leaves and root apices across two genotypes

<p>Abstract</p> <p>Background</p> <p>Comparative genomics has emerged as a promising means of unravelling the molecular networks underlying complex traits such as drought tolerance. Here we assess the genotype-dependent component of the drought-induced transcriptome response in two poplar genotypes differing in drought tolerance. Drought-induced responses were analysed in leaves and root apices and were compared with available transcriptome data from other <it>Populus </it>species.</p> <p>Results</p> <p>Using a multi-species designed microarray, a genomic DNA-based selection of probesets provided an unambiguous between-genotype comparison. Analyses of functional group enrichment enabled the extraction of processes physiologically relevant to drought response. The drought-driven changes in gene expression occurring in root apices were consistent across treatments and genotypes. For mature leaves, the transcriptome response varied weakly but in accordance with the duration of water deficit. A differential clustering algorithm revealed similar and divergent gene co-expression patterns among the two genotypes. Since moderate stress levels induced similar physiological responses in both genotypes, the genotype-dependent transcriptional responses could be considered as intrinsic divergences in genome functioning. Our meta-analysis detected several candidate genes and processes that are differentially regulated in root and leaf, potentially under developmental control, and preferentially involved in early and long-term responses to drought.</p> <p>Conclusions</p> <p>In poplar, the well-known drought-induced activation of sensing and signalling cascades was specific to the early response in leaves but was found to be general in root apices. Comparing our results to what is known in arabidopsis, we found that transcriptional remodelling included signalling and a response to energy deficit in roots in parallel with transcriptional indices of hampered assimilation in leaves, particularly in the drought-sensitive poplar genotype.</p

Effets d'une augmentation de dioxyde de carbone et d'ozone sur les échanges gazeux et la composition minérale des tissus foliaires de Quercus rubra (L), Picea abies (L.) Karst. et Fagus sylvatica (L.) cultivés en chambres à ciel ouvert ; interactions avec des déficits hydriques

This thesis presents ecophysiological measurements that were performed on different tree species to assess the impact of global pollutant changes on forests. The work has concentrated on the effects of an increase in tropospheric ozone (on two Picea abies clones and on Fagussylvatica) and on a doubling of C02 (on Picea abies and Quercus rubra). Growth, foliage gas exchange and the concentrations of nutrients at both the whole leaf and at the tissue level were studied. Furthermore the effects of combining each pollutant with drought were assessed.The growth of Picea abies at ambient + 50 ppb ozone was significantly reduced. The effect of ozone on gas exchange and nutrient levels of needles of Picea abies varied between clones. The response of beech was different to that of Norway spruce. Drought accentuated the effects of ozone on one-year-old needles of the Istebna clone, but it served to reduce the impact of ozone on beech leaves.Increasing the C02 concentration led to stomatal opening and larger net assimilation rates in red oak, but as the drought developed both oak and spruce had greater water use efficiencies in CO2 enhanced air. 700 ppm C02 had a tendency to decrease the total foliage concentration of nutrients, but this phenomenon was not consistent between different foliage tissues.Ce travail synthétise les résultats obtenus lors de mesures écophysiologiques réalisées sur différentes espèces d'arbres. L'étude s'est portée sur les impacts d'une augmentation de la concentration d'ozone troposphérique (étudiée sur deux clones de Picea abies et Fagus sylvatica) et d'une augmentation de la concentration en dioxyde de carbone (étudiée sur Picea abies et Qquercus rubra). Parallèlement, les interactions du dioxyde de carbone et de l'ozone avec une contrainte hydrique édaphique ont été analysées. La croissance des arbres soumis à l'air ambiant + 50 ppb d'ozone est réduite significativement. Les effets de l'ozone sur les échanges gazeux et la composition minérale des aiguilles de l'année et de un an varient selon les clones chez les épicéas. De même, la réponse des hêtres est différente de celle des épicéas. La sécheresse aggrave l'effet de l'ozone sur les aiguilles de un an du clone istebna, elle montre un effet protecteur chez le hêtre. L'augmentation de concentration en dioxyde de carbone provoque une stimulation de la conductance stomatique et de l'assimilation nette de dioxyde de carbone chez le hêtre ; en conditions hydriques défavorables, chênes et épicéas montrent une meilleure efficience d'utilisation de l'eau dans le traitement à forte concentration de dioxyde de carbone. L'augmentation de concentration en dioxyde de carbone tend à diminuer la concentration totale foliaire des éléments minéraux ; ce phénomène n'affecte pas tous les compartiments foliaires

Intérêt de la microscopie électronique pour des études de l’impact de stress abiotiques sur les plantes

Intérêt de la microscopie électronique pour des études de l’impact de stress abiotiques sur les plantes. Journée Microscopie des Parois Végétales. INRA / Université de Lorraine / Université de Reims Champagne-Ardenn

Intérêt de la microscopie électronique pour des études de l’impact de stress abiotiques sur les plantes

Intérêt de la microscopie électronique pour des études de l’impact de stress abiotiques sur les plantes. Journée Microscopie des Parois Végétales. INRA / Université de Lorraine / Université de Reims Champagne-Ardenn

Biopollatm : Biosphère et pollution atmosphérique en zone rurale et périurbaine. Rapport de fin de contrat

Le projet BIOPOLLATM vise à mieux comprendre les interactions biosphère-atmosphère dans le domaine de la pollution atmosphérique. On cherche (1) à comprendre les modalités d’impacts de plusieurs polluants sur le fonctionnement des plantes et (2) le rôle de la biosphère comme source et puits dans la pollution atmosphérique locale et régionale. Des caractéristiques fortes de BIOPOLLATM sont (1) une intégration entre des approches biologiques et physiques, à l’interface des sciences de la vie, de la terre et de l’atmosphère, (2) l’objet d’étude privilégié qui sont les écosystèmes cultivés en zones périurbaines et (3) l’intégration d’échelle, allant de la plante à la région selon les thématiques scientifiques et appliquées concernées. Ce rapport fait un point sur l’avancement du projet après 2 ans de travail (le projet se poursuit dans le cadre de PRIMEQUAL notamment, avec un financement du MEDD/DPPR). Il se compose de trois parties : - un rappel sur les objectifs et l’organisation du projet - un rapport plus détaillé sur les travaux conduits, organisé en trois grands domaines : o impact de l’ozone sur le fonctionnement des couverts végétaux à différentes échelles et selon différentes approches, allant de la modification des enzymes impliquées dans la photosynthèse jusqu’à la modélisation de l’impact sur le rendement des cultures ; o échanges de polluants entre un couvert végétal et l’atmosphère, organisé autour du développement et la validation d’un modèle à résistance à deux couches, destiné d’une part à être utilisé par les écophysiologistes/agronomes pour estimer les quantités de polluant absorbées par la végétation et, d’autre part, à être utilisé comme interface surface-atmosphère dans des modèles de chimie atmosphérique ; o une présentation des bases de données créées et des dispositifs expérimentaux créés dans le cadre de ce projet pour l’étude des échanges de polluants entre les surfaces naturelles et l’atmosphère. Ces acquis perdureront au delà du projet et pourront être utilisés par nos équipes et d’autres pour la poursuite de ce type de travaux. - Une synthèse des résultats acquis et une présentation des perspectives de ce travail à échéance de deux ans