Light-regulated plant growth and development.

Plants are sessile and photo-autotrophic; their entire life cycle is thus strongly influenced by the ever-changing light environment. In order to sense and respond to those fluctuating conditions higher plants possess several families of photoreceptors that can monitor light from UV-B to the near infrared (far-red). The molecular nature of UV-B sensors remains unknown, red (R) and far-red (FR) light is sensed by the phytochromes (phyA-phyE in Arabidopsis) while three classes of UV-A/blue photoreceptors have been identified: cryptochromes, phototropins, and members of the Zeitlupe family (cry1, cry2, phot1, phot2, ZTL, FKF1, and LKP2 in Arabidopsis). Functional specialization within photoreceptor families gave rise to members optimized for a wide range of light intensities. Genetic and photobiological studies performed in Arabidopsis have shown that these light sensors mediate numerous adaptive responses (e.g., phototropism and shade avoidance) and developmental transitions (e.g., germination and flowering). Some physiological responses are specifically triggered by a single photoreceptor but in many cases multiple light sensors ensure a coordinated response. Recent studies also provide examples of crosstalk between the responses of Arabidopsis to different external factors, in particular among light, temperature, and pathogens. Although the different photoreceptors are unrelated in structure, in many cases they trigger similar signaling mechanisms including light-regulated protein-protein interactions or light-regulated stability of several transcription factors. The breath and complexity of this topic forced us to concentrate on specific aspects of photomorphogenesis and we point the readers to recent reviews for some aspects of light-mediated signaling (e.g., transition to flowering).

Oeuvres complètes de Tabarin : avec les Rencontres, fantaisies et coq-à-l'âne facétieux du baron de Gratelard , et divers opuscules publiés séparément sous le nom ou à propos de Tabarin. Tome 1 / Le tout précédé d'une introduction et d'une bibliographie tabarinique par Gustave Aventin

Collection : Bibliothèque elzévirienne ; 65, 1-2

Oeuvres complètes de Tabarin : avec les Rencontres, fantaisies et coq-à-l'âne facétieux du baron de Gratelard , et divers opuscules publiés séparément sous le nom ou à propos de Tabarin. Tome 2 / Le tout précédé d'une introduction et d'une bibliographie tabarinique par Gustave Aventin

Collection : Bibliothèque elzévirienne ; 65, 1-2

Oeuvres complètes de Tabarin : avec les Rencontres, fantaisies et coq-à-l'âne facétieux du baron de Gratelard , et divers opuscules publiés séparément sous le nom ou à propos de Tabarin. Tome 2 / Le tout précédé d'une introduction et d'une bibliographie tabarinique par Gustave Aventin

Collection : Bibliothèque elzévirienne ; 65, 1-2

Oeuvres complètes de Tabarin : avec les Rencontres, fantaisies et coq-à-l'âne facétieux du baron de Gratelard , et divers opuscules publiés séparément sous le nom ou à propos de Tabarin. Tome 1 / Le tout précédé d'une introduction et d'une bibliographie tabarinique par Gustave Aventin

Collection : Bibliothèque elzévirienne ; 65, 1-2

Le mystère de la Passion / d'Arnoul Greban ; publié d'après les manuscrits de Paris, avec une introduction et un glossaire, par Gaston Paris et Gaston Raynaud

[Mystère de la Passion (français moyen). 1878]

Radial transport of nutrients: the plant root as a polarized epithelium.

In higher plants, roots acquire water and soil nutrients and transport them upward to their aerial parts. These functions are closely related to their anatomical structure; water and nutrients entering the root first move radially through several concentric layers of the epidermis, cortex, and endodermis before entering the central cylinder. The endodermis is the innermost cortical cell layer that features rings of hydrophobic cell wall material called the Casparian strips, which functionally resemble tight junctions in animal epithelia. Nutrient uptake from the soil can occur through three different routes that can be interconnected in various ways: the apoplastic route (through the cell wall), the symplastic route (through cellular connections), and a coupled trans-cellular route (involving polarized influx and efflux carriers). This Update presents recent advances in the radial transport of nutrients highlighting the coupled trans-cellular pathway and the roles played by the endodermis as a barrier.

Introduction du Dossier "Affecter, être affecté. Autour des travaux de Jeanne Favret-Saada"

Dossiers, Affecter, être affecté. Autour des travaux de Jeanne Favret-Saada, mis en ligne le 24 juin 2014

The cuticle: Not only a barrier for plant defence: A novel defence syndrome in plants with cuticular defects.

The cuticle is a physical barrier that prevents water loss and protects against irradiation, xenobiotics and pathogens. This classic textbook statement has recently been revisited and several observations were made showing that this dogma falls short of being universally true. Both transgenic Arabidopsis thaliana lines expressing cell wall-targeted fungal cutinase (so-called CUTE plants) or lipase as well as several A. thaliana mutants with altered cuticular structure remained free of symptoms after an inoculation with Botrytis cinerea. The alterations in cuticular structure lead to the release of fungitoxic substances and changes in gene expression that form a multifactorial defence response. Several models to explain this syndrome are discussed.

Relatedness among arbuscular mycorrhizal fungi drives plant growth and intraspecific fungal coexistence.

Arbuscular mycorrhizal fungi (AMF) form symbioses with most plant species. They are ecologically important determinants of plant growth and diversity. Considerable genetic variation occurs in AMF populations. Thus, plants are exposed to AMF of varying relatedness to each other. Very little is known about either the effects of coexisting AMF on plant growth or which factors influence intraspecific AMF coexistence within roots. No studies have addressed whether the genetics of coexisting AMF, and more specifically their relatedness, influences plant growth and AMF coexistence. Relatedness is expected to influence coexistence between individuals, and it has been suggested that decreasing ability of symbionts to coexist can have negative effects on the growth of the host. We tested the effect of a gradient of AMF genetic relatedness on the growth of two plant species. Increasing relatedness between AMFs lead to markedly greater plant growth (27% biomass increase with closely related compared to distantly related AMF). In one plant species, closely related AMF coexisted in fairly equal proportions but decreasing relatedness lead to a very strong disequilibrium between AMF in roots, indicating much stronger competition. Given the strength of the effects with such a shallow relatedness gradient and the fact that in the field plants are exposed to a steeper gradient, we consider that AMF relatedness can have a strong role in plant growth and the ability of AMF to coexist. We conclude that AMF relatedness is a driver of plant growth and that relatedness is also a strong driver of intraspecific coexistence of these ecologically important symbionts.