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International audience; Carbon management by plants involves the activity of many sugar transporters, which play roles in sugar subcellular partitioning and reallocation at the whole organism scale. Among these transporters, the early response to dehydration six-like (ESL) monosaccharide transporters (MSTs) are still poorly characterized although they represent one of the largest sugar transporter subfamilies. In this study, we used an evolutionary genomic approach to infer the evolutionary history of this multigenic family. No ESL could be identified in the genomes of rhodophytes, chlorophytes, and the brown algae Ectocarpus siliculosus , whereas one ESL was identified in the genome of Klebsormidium nitens providing evidence for the early emergence of these transporters in Streptophytes. A phylogenetic analysis using the 519 putative ESL proteins identified in the genomes of 47 Embryophyta species and being representative of the plant kingdom has revealed that ESL protein sequences can be divided into three major groups. The first and second groups originated in the common ancestor of all spermaphytes [ζ: 340 million years ago (MYA)] and of angiosperms (ε: 170–235 MYA), respectively, and the third group originated before the divergence of rosids and asterids (γ/1R: 117 MYA). In some eudicots (Vitales, Malpighiales, Myrtales, Sapindales, Brassicales, Malvales, and Solanales), the ESL family presents remarkable expansions of gene copies associated with tandem duplications. The analysis of non-synonymous and synonymous substitutions for the dN/dS ratio of the ESL copies of the genus Arabidopsis has revealed that ESL genes are evolved under a purifying selection even though the progressive increase of dN/dS ratios in the three groups suggests subdiversification phenomena. To further explore the possible acquisition of novel functions by ESL MSTs, we identified the gene structure and promoter cis -acting elements for Arabidopsis thaliana ESL genes. The expression profiling of Arabidopsis ESL unraveled some gene copies that are almost constitutively expressed, whereas other gene copies display organ-preferential expression patterns. This study provides an evolving framework to better understand the roles of ESL transporters in plant development and response to environmental constraints.

International audience; Drought is one of the main abiotic stresses, which affects plant growth, development, and crop yield. Plant response to drought implies carbon allocation to sink organs and sugar partitioning between different cell compartments, and thereby requires the involvement of sugar transporters (SUTs). Among them, the early response to dehydration six-like (ESL), with 19 members in Arabidopsis thaliana , form the largest subfamily of monosaccharide transporters (MSTs) still poorly characterized. A common feature of these genes is their involvement in plant response to abiotic stresses, including water deficit. In this context, we carried out morphological and physiological phenotyping of A. thaliana plants grown under well-watered (WW) and water-deprived (WD) conditions, together with the expression profiling of 17 AtESL genes in rosette leaves. The drought responsiveness of 12 ESL genes, 4 upregulated and 8 downregulated, was correlated to different water statuses of rosette leaves. The differential expression of each of the tandem duplicated AtESL genes in response to water stress is in favor of their plausible functional diversity. Furthermore, transfer DNA (T-DNA) insertional mutants for each of the four upregulated ESLs in response to water deprivation were identified and characterized under WW and WD conditions. To gain insights into global sugar exchanges between vacuole and cytosol under water deficit, the gene expression of other vacuolar SUTs and invertases ( AtTMT, AtSUC, AtSWEET , and At β FRUCT ) was analyzed and discussed.

International audience; Abstract The initial greening of angiosperm occurs upon light-activation of photoreceptors that trigger photomorphogenesis followed with the development of chloroplasts. In these semi-autonomous organelles, the construction of the photosynthetic apparatus depends on the coordination of nuclear and plastid gene expression. Here we show that PAP8, as an essential subunit of the plastid-encoded RNA polymerase, is under the control of a regulatory element recognized by the photomorphogenic factor HY5. PAP8 is localized and active in both plastids and the nucleus and particularly essential for the formation of late photobodies. In the albino pap8 mutant, phytochrome-mediated signalling is altered, PIFs are maintained, HY5 is not stabilized, and GLK1 expression is impaired. PAP8 translocates into plastids losing its pre-sequence, interacts with the PEP, and using an unknown route or a retrograde transport, reaches the nucleus where it has the ability to interact with pTAC12/HMR/PAP5. Since PAP8 is required for the phytochrome-B-mediated signalling cascade and the reshaping of the PEP, it may coordinate nuclear gene expression with the PEP-driven chloroplastic gene expression during chloroplast biogenesis.

A novel biological model was created for the comparison of grapevine embryogenic cells (EC) and nonembryogenic cells (NEC) sharing a common genetic background but distinct phenotypes, when cultured on their respective most appropriate media. Cytological characterization, 1H‐NMR analysis of intracellular metabolites, and glycolytic enzyme activities provided evidence for the marked metabolic differences between EC and NEC. The EC were characterized by a moderate and organized cell proliferation, coupled with a low flux through glycolysis, high capacity of phosphoenolpyruvate carboxylase and glucokinase, and high oxygen consumption. The NEC displayed strong anarchic growth, and their high rate of glycolysis due to the low energetic efficiency of the fermentative metabolism is confirmed by increased enolase capacity and low oxygen consumption.

International audience; Background and Aims: Esca is a devastating wood-decay disease that affects major grape-producing areas around the world. Xylem pathogenic fungi produce a systemic effect on the development of foliar symptoms and glutathione metabolism in presence of oxidative species. This study focuses on sugar variations in Vitis vinifera leaves, in particular in early events occurring in esca. Methods and Results: Biochemical, cytochemical and molecular methods showed that in esca-infected grapevines, photosynthetic pigment content did not vary significantly in leaves from apparently healthy canes (AC-AL), but decreased in leaves without symptoms on symptomatic canes (SC-AL). Starch grains were more abundant in AC-AL than in SC-AL containing wide plastoglobuli and numerous tannins. The starch level increased early, and then decreased with esca development. Fructose increased early by more than threefold, being the predominant soluble sugar in leaves with advanced esca symptoms. Conclusions: In response to damage induced by fungal infection, defence reactions such as fructose increased early and developed in esca leaves to scavenge reactive oxygen species and protect plant tissues. Significance of the Study: Esca infection leads to an early production of fructose involved in defence.

Legendre François, Lorgnet Jean-Paul, Thibault Florence. Une allocation d’autonomie pour les jeunes [Quatre scénarios évalués par le modèle de microsimulation MYRIADE]. In: Recherches et Prévisions, n°75, 2004. pp. 100-106.

L’objet de cet article est de présenter les modèles socio-économiques de microsimulation. Les auteurs détaillent les principes mis en oeuvre dans ce type d’outil et exposent les principaux modèles existant actuellement en France. Est également passée en revue une sélection de questions qui peuvent être adressées à ces modèles. Le lecteur peut ainsi être en mesure d’apprécier l’état de l’art dans ce domaine et se faire une idée plus précise des avantages et des limites de ces méthodes. Cependant, l’article s’intéresse avant tout aux outils dont l’ambition est de décrire, plus ou moins globalement, le système des prélèvements obligatoires et des transferts sociaux. Ne sont pas évoqués les outils développés pour les besoins de thèmes plus spécifiques tels que l’économie de la santé ou l’économie du droit., Legendre François, Lorgnet Jean-Paul, Thibault Florence. Les modèles socio-économiques de microsimulation [Panorama et état des lieux pour la France]. In: Recherches et Prévisions, n°66, 2001. Évaluer les politiques familiales et sociales. MYRIADE, un outil de microsimulation à la CNAF. pp. 11-31.