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International audience; Germination is a traditional process and a re-emerging trend in healthy foods, resulting a progressively increase in scientific research on their nutritional traits and phytochemical contents. This review examines the physiological and biochemical changes during the germination sensu stricto in pulses, taking into consideration the genotype, environmental conditions, hormone control, and the metabolic transition from seed to seedling. Germination sensu stricto is achieved as soon as elongation of the radicle, implies heterotrophy metabolism; further thermal processing is needed before consumption. In contrast, seedlings production requires a long period of imbibition and can provide a ready-to-eat food product. Furthermore, proteins, carbohydrates, minerals, vitamins, and antinutritional compounds of pulses are described. Impacts of food processing, such as soaking, germination, and cooking, in nutritional and antinutritional values are also evaluated. The association of soaking, germination, and cooking increases the nutritional values of pulses by increasing protein/starch digestibility and vitamins content and by decreasing antinutritional compounds. The final plant-based product allows versatility in formulation to produce novel food products and/or ingredients with better nutritional content. This can encourage the scientific community, industry, and government to invest in research and development to increase germinated pulse-based food, to replace other products, or to develop new ones.

International audience; Effects of anthropogenic activities such as urbanisation, population growth and agriculture on water quality are major concerns particularly in low-income countries where water quality monitoring can be challenging. The purpose of this study was to evaluate the cytogenotoxic potential of water from urban and rural Malagasy marshes, coupling a fish (Nile tilapia Oreochromis niloticus) and a plant (Allium cepa) species as bioindicators. The fish and plants were exposed for 72 h to water sampled in the two locations investigated. DNA strand breaks were assessed using the comet assay on fish erythrocytes, while mitotic index and nucleolar alterations were estimated in cells of the plant root apex. Comet assays revealed significant DNA strand breaks to fish erythrocytes in both the marshes investigated while the mitotic index and nucleolar characteristics in the roots of A. cepa mainly highlighted potential cytotoxicity in the urban marsh. Our results demonstrate the advantages of coupling in vivo biological test systems to screen potential cytogenotoxicity of surface water in low-income countries where comprehensive datasets of aquatic contaminants are often lacking. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. (c) 2023 SETAC.

Quantifying healthy and degraded inner tissues in plants is of great interest in agronomy, for example, to assess plant health and quality and monitor physiological traits or diseases. However, detecting functional and degraded plant tissuesin-vivowithout harming the plant is extremely challenging. New solutions are needed in ligneous and perennial species, for which the sustainability of plantations is crucial. To tackle this challenge, we developed a novel approach based on multimodal 3D imaging and Artificial Intelligence (AI)-based image processing that allowed a noninvasive diagnosis of inner tissues in living plants. The method was successfully applied to the grapevine (Vitis viniferaL.) in vineyards where sustainability was threatened by trunk diseases, while the sanitary status of vines cannot be ascertained without injuring the plants. By combining MRI and X-ray CT 3D imaging with an automatic voxel classification, we could discriminate intact, degraded, and white rot tissues with a mean global accuracy of over 91%. Each imaging modality contribution to tissue detection was evaluated, and we identified quantitative structural and physiological markers characterizing wood degradation steps. The combined study of inner tissue distributionversusexternal foliar symptom history demonstrated that white rot and intact tissue contents are key measurements in evaluating vines’ sanitary status. We finally proposed a model for an accurate trunk disease diagnosis in grapevine. This work opens new routes for precision agriculture andin-situmonitoring of wood quality and plant health across plant species.

The growth and composition of fleshy fruits depend on resource acquisition and distribution in the plant. In tomato, the pedicel serves as the final connection between plant and fruit. However, very few quantitative data are available for the conducting tissues of the pedicel, nor is their genetic variability known. In the present study, a histological approach was combined with process-based modeling to evaluate the potential contribution made by the anatomy and histology of the pedicel to variations in fruit mass. Eleven genotypes were characterized and the impact of water deficit was studied for a single genotype using stress intensity and stage of application as variables. The results highlighted extensive variations in the relative proportions of the different pedicel tissues and in the absolute areas of xylem and phloem between genotypes. The model suggests that the variations in the area of the pedicel's vascular tissues induced by differences in genotype and water-deficit environments partly contributed to fruit mass variability. They therefore warrant phenotyping for use in the development of plant strains adapted to future environmental constraints. The results also demonstrated the need to develop non-invasive in vivo measurement methods to establish the number and size of active vessels and the flow rates in these vessels to improve prediction of water fluxes in plant architecture.

Conductive tissues are main routes of resource transport, that are crucial for the growth of fleshy fruit. Yet, very few quantitative data of xylem and phloem areas are available and their variabilities are unknown. This study aimed at better understanding and quantifying the structural and functional properties of the conductive tissues in tomato pedicel. 11 contrasting genotypes were described and the impact of water deficit was studied depending on stress intensity and stage of application. In parallel, MRI was used to assess the proportion and size of active xylem vessels in the stem. Results were implemented in a Virtual Fruit model to assess the potential contribution of pedicel conductive tissues in the variability of fruit fresh and dry masses. On their whole, results suggested that variations in the properties of conducting tissues are involved in the genotypic and environmental variations of fruit mass. The study also highlights the interest to combine methods and to integrate knowledge to better understand plant functioning, and finally to improve plant models. Flow-MRI was shown to be an easy non-destructive method to measure the functional properties of conducting tissues such as the proportion of active vessels and their diameter.

The success of fertilization depends on an array of complex physical and physiological interactions between the pollen and the pistil. To better understand the fertilization process in Malagasy baobabs, pistil structure and pollen tube growth were investigated in three species of Adansonia: A. grandidieri (section Brevitubae), A. madagascariensis and A. rubrostipa (Longitubae section). The pistil consists of an ovary with 6–9 locules, a very long hollow type style and six to nine lobed wet, papillate stigma. The pollen tubes grow in intercellular secretions in the stigma and join the stylar canal to reach the locule of the ovary and then the micropyle of the ovules. The size of the central stylar canal shrinks as it approaches the ovary. This restriction leads to gametophytic competition by reducing the number of pollen tubes that reach the ovules. The pollen tubes reach the ovules four to six days after pollination. The pollen tubes of the two Longitubae species grow faster than those of A. grandidieri. This information on the progamic phase of baobabs is essential to understand the mode of reproduction of baobabs.

Vascular tissues are main routes of resource transport, which are crucial for the growth of fleshy fruit. Very few quantitative data of the total and active areas of xylem and phloem are available for herbaceous plants and their variabilities are unknown. In this study, histological approach and process-based modeling of tomato fruit growth were combined to evaluate the potential contribution of the pedicel anatomy to fruit mass variations. Eleven genotypes were described and the impact of water deficit was studied depending on stress intensity and stage of application. In parallel, MRI experiments allowed to better understand the source of variability in xylem flow along the main stem. Our results suggested that the genetic and water deficit-induced variations in the areas of vascular tissues in the pedicel partly contributed to fruit mass variability. Flow-MRI appeared to be a complementary non-destructive method to phenotype vascular tissues. Whereas the flow velocity in active xylem vessels was rather stable along the main stem, the decrease in the number of active vessels strongly reduces the effective flow from the bottom to the top of the plant. Fruitful interactions between modeling, histology and flow-MRI are promising and worth exploring, to predict water fluxes within plant architecture.

International audience; Potassium (K(+)) nutrition is of relevant interest for winegrowers because it influences grapevine growth, berry composition, as well as must and wine quality. Indeed, wine quality strongly depends on berry composition at harvest. However, K(+) content of grape berries increased steadily over the last decades, in part due to climate change. Currently, the properties and qualities of many fruits are also impacted by environment. In grapevine, this disturbs berry properties resulting in unbalanced wines with poor organoleptic quality and low acidity. This requires a better understanding of the molecular basis of K(+) accumulation and its control along grape berry development. This mini-review summarizes our current knowledge on K(+) nutrition in relation with fruit quality in the context of a changing environment.

International audience; Grapevine (Vitis vinifera L.), one of the most important fruit crops, is a model plant for studying the physiology of fleshy fruits. Here, we report on the characterization of a new grapevine Shaker-type K+ channel, VvK5.1. Phylogenetic analysis revealed that VvK5.1 belongs to the SKOR-like subfamily. Our functional characterization of VvK5.1 in Xenopus oocytes confirms that it is an outwardly rectifying K+ channel that displays strict K+ selectivity. Gene expression level analyses by real-time quantitative PCR showed that VvK5.1 expression was detected in berries, roots, and flowers. In contrast to its Arabidopsis thaliana counterpart that is involved in K+ secretion in the root pericycle, allowing root to shoot K+ translocation, VvK5.1 expression territory is greatly enlarged. Using in situ hybridization we showed that VvK5.1 is expressed in the phloem and perivascular cells of berries and in flower pistil. In the root, in addition to being expressed in the root pericycle like AtSKOR, a strong expression of VvK5.1 is detected in small cells facing the xylem that are involved in lateral root formation. This fine and selective expression pattern of VvK5.1 at the early stage of lateral root primordia supports a role for outward channels to switch on cell division initiation.

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The occurrence of somaclonal variants (ca 5%) among populations of somatic embryo-derived oil palms (Elaeis guineensis Jacq.) currently hampers the scaling-up of clonal plant production. In order to investigate the relationship between the "mantled" somaclonal variant and possible alterations in genomic DNA methylation rate, two complementary approaches have been used. HPLC quantification of relative amounts of 5-methyl-deoxycytidine has shown that global methylation in leaf DNA of abnormal regenerants is 0.5-2.5% lower than in their normal counterparts (20.8% vs 22%, respectively). When comparing nodular compact calli and fast growing calli, yielding respectively 5% and 100% of "mantled" plantlets, this decrease was up to 4.5% (from 23.2 to 18.7%). An alternative method, the Sssl-methylase accepting assay, based on the enzymatic saturation of CG sites with methyl groups, gave convergent results. This work demonstrates that a correlation exists between DNA hypomethylation and the "mantled" somaclonal variation in oil palm.

In grapevine, climate changes lead to increased berry potassium (K+ ) contents that result in must with low acidity. Consequently, wines are becoming 'flat' to the taste, with poor organoleptic properties and low potential aging, resulting in significant economic loss. Precise investigation into the molecular determinants controlling berry K+ accumulation during its development are only now emerging. Here, we report functional characterization by electrophysiology of a new grapevine Shaker-type K+ channel, VvK3.1. The analysis of VvK3.1 expression patterns was performed by qPCR and in situ hybridization. We found that VvK3.1 belongs to the AKT2 channel phylogenetic branch and is a weakly rectifying channel, mediating both inward and outward K+ currents. We showed that VvK3.1 is highly expressed in the phloem and in a unique structure located at the two ends of the petiole, identified as a pulvinus. From the onset of fruit ripening, all data support the role of the VvK3.1 channel in the massive K+ fluxes from the phloem cell cytosol to the berry apoplast during berry K+ loading. Moreover, the high amount of VvK3.1 transcripts detected in the pulvinus strongly suggests a role for this Shaker in the swelling and shrinking of motor cells involved in paraheliotropic leaf movements.

International audience; Grenache Noir and Syrah are two of the grapevine (Vitis vinifera L.) cultivars used to a great extent worldwide. They have very different leaf morphologies from an ampelographic (botanical) point of view. This might also be related to differences in the anatomy and micro-morphology of their leaves. The goal of the present work was to compare these cultivar's leaf anatomy and morphology. Adult leaves from both cultivars were characterised using a range of microscopy techniques. Grenache Noir had a significantly smaller leaf surface area, but a significantly thicker leaf blade, than Syrah. It also had significantly larger stomata and a larger stomatal index than Syrah. The distribution of mesophyll tissues was similar in both cultivars, but the upper epidermis was significantly thicker in Grenache Noir, and the palisade parenchyma cells were longer in Syrah. The mesophyll tissues of both cultivars contained abundant idioblasts carrying crystals of calcium oxalate and mucilage. This work reveals quantitative and qualitative differences in the anatomy and morphology of mature Grenache Noir and Syrah leaves. Further work is needed to determine how these anatomical and morphological differences may be connected with different responses at the functional level.

International audience; The thickness of grain pericarp, the outer layer of the kernel, is an important breeding criterion for sorghum. This cereal is mainly used through traditional processing in family-based food systems in many regions of the world. We investigated in this study how pericarp thickness could be predicted by Near Infrared Reflectance Spectroscopy (NIRS), a fast and non-destructive measurement method that is commonly used to measure physico-chemical parameters of sorghum grains, and how this trait also influences the prediction of those parameters. We showed that, using a classification approach, it was possible to discriminate thick from thin pericarp whole grain samples with a good accuracy and that the proportion of thin and thick grains in mixed samples could also be predicted. In addition, pericarp thickness had a significant effect on the calibration performance for other grain parameters indicating that the pericarp can distort spectral information of whole grain samples. As a practical consequence, we suggest to develop separate whole grain calibration models for thin and thick pericarp samples, combined with a two-steps prediction approach to improve the accuracy of whole grain NIRS calibrations for grain quality parameters in sorghum.

In grapevine, climate changes lead to increased berry potassium (K

International audience; Sorghum is expected to contribute significantly to the growing needs of ligno cellulosic biomass that will support the productions of renewable energy, biomaterials and innovative biorefinery approaches. The agronomic and genetic assets of sorghum will facilitate these contributions. Nevertheless, in order to fine tune the varieties to the expectations of the growers (agronomic behavior) and of the different value chains (quality parameters) there is a crucial need to i) optimize the production process of sorghum based derived products and ii) to accurately define the target ideotypes to consider in breeding programs depending on the end-products and contexts considered. As a first step, we considered three end products: methane, biocomposite and feed. For the first two targets, we optimized the process of production by adjusting the pre-treatments and fine tuning-the different steps of the processes. As a second step we aimed at identifying the sorghum traits that contributed to the final properties of the end products. To reach this objective, we characterized at the biochemical, histological and physical levels a panel of diversity that encompassed most of the chemical variability of sorghum biomass. This panel was also characterized for its feed and biocomposite properties and for its biomethane production potential. This allowed the identification of the sets of biomass properties to target for the different end-products. As a last step, specifically for the energy targets (methane and second generation ethanol), we performed a spatially based multicriteria analysis at the regional level (anchoring the analysis on the French Midi Pyrenées region) to assess the relevance of different types of crop management and end product value chains in accordance with the local constraints (i.e. water availability, technical context). These three steps provided us with a decision tool to orientate breeding efforts depending on the targeted end-product, the environmental and technical contexts.

Two different mechanisms controlling the Theobroma cacao self-incompatibility system were identified at two separate loci together with candidate genes differentially expressed between self-compatible/incompatible reactions, and diagnostic markers predicting self-compatible varieties were produced., Cocoa self-compatibility is an important yield factor and has been described as being controlled by a late gameto-sporophytic system expressed only at the level of the embryo sac. It results in gametic non-fusion and involves several loci. In this work, we identified two loci, located on chromosomes 1 and 4 (CH1 and CH4), involved in cocoa self-incompatibility by two different processes. Both loci are responsible for gametic selection, but only one (the CH4 locus) is involved in the main fruit drop. The CH1 locus acts prior to the gamete fusion step and independently of the CH4 locus. Using fine-mapping and genome-wide association studies, we focused analyses on restricted regions and identified candidate genes. Some of them showed a differential expression between incompatible and compatible reactions. Immunolocalization experiments provided evidence of CH1 candidate genes expressed in ovule and style tissues. Highly polymorphic simple sequence repeat (SSR) diagnostic markers were designed in the CH4 region that had been identified by fine-mapping. They are characterized by a strong linkage disequilibrium with incompatibility alleles, thus allowing the development of efficient diagnostic markers predicting self-compatibility and fruit setting according to the presence of specific alleles or genotypes. SSR alleles specific to self-compatible Amelonado and Criollo varieties were also identified, thus allowing screening for self-compatible plants in cocoa populations.

We report here the isolation and functional analysis of AlTMP1 gene encoding a member of the PMP3 protein family. In Aeluropus littoralis, AlTMP1 is highly induced by abscisic acid (ABA), cold, salt, and osmotic stresses. Transgenic tobacco expressing AlTMP1 exhibited enhanced tolerance to salt, osmotic, H2O2, heat and freezing stresses at the seedling stage. Under greenhouse conditions, the transgenic plants showed a higher level of tolerance to drought than to salinity. Noteworthy, AlTMP1 plants yielded two- and five-fold more seeds than non-transgenic plants (NT) under salt and drought stresses, respectively. The leaves of AlTMP1 plants accumulated lower Na+ but higher K+ and Ca2+ than those of NT plants. Tolerance to osmotic and salt stresses was associated with higher membrane stability, low electrolyte leakage, and improved water status. Finally, accumulation of AlTMP1 in tobacco altered the regulation of some stress-related genes in either a positive (NHX1, CAT1, APX1, and DREB1A) or negative (HKT1 and KT1) manner that could be related to the observed tolerance. These results suggest that AlTMP1 confers stress tolerance in tobacco through maintenance of ion homeostasis, increased membrane integrity, and water status. The observed tolerance may be due to a direct or indirect effect of AlTMP1 on the expression of stress-related genes which could stimulate an adaptive potential not present in NT plants.

The oil palm (Elaeis guineensis), a monocotyledonous species in the family Arecaceae, has an extraordinarily oil rich fleshy mesocarp, and presents an original model to examine the ripening processes and regulation in this particular monocot fruit. Histochemical analysis and cell parameter measurements revealed cell wall and middle lamella expansion and degradation during ripening and in response to ethylene. Cell wall related transcript profiles suggest a transition from synthesis to degradation is under transcriptional control during ripening, in particular a switch from cellulose, hemicellulose, and pectin synthesis to hydrolysis and degradation. The data provide evidence for the transcriptional activation of expansin, polygalacturonase, mannosidase, beta-galactosidase, and xyloglucan endotransglucosylase/hydrolase proteins in the ripening oil palm mesocarp, suggesting widespread conservation of these activities during ripening for monocotyledonous and eudicotyledonous fruit types. Profiling of the most abundant oil palm polygalacturonase (EgPG4) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) transcripts during development and in response to ethylene demonstrated both are sensitive markers of ethylene production and inducible gene expression during mesocarp ripening, and provide evidence for a conserved regulatory module between ethylene and cell wall pectin degradation. A comprehensive analysis of NAC transcription factors confirmed at least 10 transcripts from diverse NAC domain clades are expressed in the mesocarp during ripening, four of which are induced by ethylene treatment, with the two most inducible (EgNAC6 and EgNAC7) phylogenetically similar to the tomato NAC-NOR master-ripening regulator. Overall, the results provide evidence that despite the phylogenetic distance of the oil palm within the family Arecaceae from the most extensively studied monocot banana fruit, it appears ripening of divergent monocot and eudicot fruit lineages are regulated by evolutionarily conserved molecular physiological processes.

Equipe DAVEM = Diversité et Adaptation de la Vigne et des Espèces Méditerranéennes; International audience; Background and Aims Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. Methods Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. Key Results and Conclusions The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.

Le riz ( Oryza sativa L.) a le double statut de cereale la plus consommee par l’homme et d’espece modele pour les monocotyledones. Elucider la fonction des genes sous-tendant les principaux caracteres d’interet agronomique chez cette plante contribuerait donc a accelerer non seulement l’amelioration varietale du riz mais aussi celle des autres cereales. La transformation genetique est un outil permettant d’accelerer la decouverte de la fonction des genes et l’innovation varietale. La premiere plante transgenique de riz a ete obtenue des 1988, et, depuis, les technologies ont regulierement evolue vers plus d’efficacite et de precision. Nous presentons ici les grandes etapes de l’evolution de ces techniques, ainsi que leurs applications pour l’analyse fonctionnelle des genes. En particulier, les perspectives ouvertes par de nouveaux sauts technologiques en cours, qui permettent a present une modification ciblee des genomes sans introduction d’acide desoxyribonucleique (ADN) superflu, seront illustrees et discutees.

In Coffea arabica L., the development of direct sowing of somatic embryos (SE) in planting substrate, with subsequent nursery production of plants, has promoted the industrialization of somatic embryogenesis. However, plant conversion rates are still low and require improvements to enhance the cost-effectiveness of commercial micropropagation. With the aim of improving plant regeneration from SE, we studied the morphological and histological criteria and water characteristics during germination and plant conversion of zygotic embryos (ZE) and SE. At the cotyledonary stage, SE produced in a 1 l RITA(®) temporary immersion bioreactor (area 55.8 cm(2)) were morphologically similar in size (2-3 mm) but abnormal as compared with mature ZE. Protein and starch reserve levels were extremely low throughout germination and conversion to plantlets, while the water status remained steady [water content (WC) from 76 to 87%, Ψ from -0.37 to -0.47 MPa, pressure potential from 0.69 to 0.24 MPa]. In ZE, spectacular hydration occurred during the first 3 weeks (WC from 37 to 75%; Ψ from -6.24 to -1.0 MPa). Cotyledons remained undifferentiated for 10 weeks after sowing. Conversely, after only 3 weeks under germination conditions in a RITA(®) bioreactor, spongy and palisade parenchyma and stomata formed in SE cotyledons. The ZE plant conversion was faster than that of SE (14 vs. 22 weeks) and more efficient (rates 96 vs. 55%), with much more substantial hypocotyl and cotyledon development. The use of a new 5 l MATIS(®) bioreactor (area 355 cm(2)), designed especially to favor embryo dispersion and light transmittance to SE, markedly improved the embryo-to-plantlet conversion rate (91%). These results highlight the morphological heterogeneity and lack of protein reserves in SE at the beginning of the germination phase and marked differences in water characteristics. However, they also reveal high phenotypic plasticity, leading to a highly efficient plantlet conversion rate due to better embryo dispersion and light transmittance in more horizontal bioreactors.

La conservación in vitro de Dioscorea alata L. clon Caraqueño es fundamental para garantizar la propagación y distribución de material de plantación sano a los productores, y disponer de un banco in vitro de un clon de gran valor agronómico y comercial en la región oriental de Cuba. Con el fin de evaluar las modificaciones anatómicas que se producen en plantas de ñame en tres condiciones de cultivo in vitro: plantas conservadas por métodos de mínimo crecimiento, plantas regeneradas y plantas en fase de multiplicación en el medio MS 75 %, se realizó un análisis de la anatomía foliar y caulinar a partir de cortes transversales de la lámina foliar y del tallo, y cortes longitudinales y transversales de microtubérculos formados durante el proceso de conservación. Las hojas de las plantas conservadas mostraron menor espesor del mesófilo y la epidermis y el área de los haces conductores del tallo también fue menor, debido al proceso de stress durante la conservación in vitro. Sin embargo, durante la recuperación del material conservado a través de la regeneración y la multiplicación in vitro se restablecieron de manera normal estos parámetros. También se evidenció que los microtubérculos formados en la conservación in vitro, poseen parénquima amilífero con abundantes gránulos de almidón, capa delgada de parénquima cortical, y haces conductores poco desarrollados, todo lo cual indica la presencia de actividad meristemática.Palabras clave: caracterización anatómica, conservación in vitro, microtubérculos, ñame, segmentos nodales The in vitro conservation of Dioscorea alata L. clone Caraqueño is fundamental to guarantee the propagation and distribution of healthy plantation material to the farmers and the establishment of one in vitro bank of this clone of great agronomic and commercial value in the Oriental Region of Cuba. With the purpose of evaluating the anatomical modifications that take place in yam plants under three in vitro culture conditions: conserved plants by slow growth, regenerated plants and in plants multiplication phase in MS 75% medium, was carried out an analysis of the foliar and caulinar anatomy from transversal cuts of the foliar sheet and of the stem, and longitudinal and transversal cuts of microtubers formed during the conservation process. Smaller thickness of the mesophyll and of the epidermis in the leaves of the conserved plants were showed and the conductive sheaves area of the stem were also smaller, due to the stress process during the in vitro conservation. However during the recovery of the conserved material through the regeneration and the in vitro multiplication were reestablished to their normal state these parameters. It was also evidenced that the microtubers formed in the in vitro conservation, have reserve parenchyma with abundant starch granules, thin cortical parenchyma and conductive sheaves little developed were determined. All this characteristics indicated the presence of meristematic activity.Key words: Anatomical characterization; In vitro conservation; In vitro tubers; Nodal cutting; Yam

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Background Drought is a widespread limiting factor in coffee plants. It affects plant development, fruit production, bean development and consequently beverage quality. Genetic diversity for drought tolerance exists within the coffee genus. However, the molecular mechanisms underlying the adaptation of coffee plants to drought are largely unknown. In this study, we compared the molecular responses to drought in two commercial cultivars (IAPAR59, drought-tolerant and Rubi, drought-susceptible) of Coffea arabica grown in the field under control (irrigation) and drought conditions using the pyrosequencing of RNA extracted from shoot apices and analysing the expression of 38 candidate genes. Results Pyrosequencing from shoot apices generated a total of 34.7 Mbp and 535,544 reads enabling the identification of 43,087 clusters (41,512 contigs and 1,575 singletons). These data included 17,719 clusters (16,238 contigs and 1,575 singletons) exclusively from 454 sequencing reads, along with 25,368 hybrid clusters assembled with 454 sequences. The comparison of DNA libraries identified new candidate genes (n = 20) presenting differential expression between IAPAR59 and Rubi and/or drought conditions. Their expression was monitored in plagiotropic buds, together with those of other (n = 18) candidates genes. Under drought conditions, up-regulated expression was observed in IAPAR59 but not in Rubi for CaSTK1 (protein kinase), CaSAMT1 (SAM-dependent methyltransferase), CaSLP1 (plant development) and CaMAS1 (ABA biosynthesis). Interestingly, the expression of lipid-transfer protein (nsLTP) genes was also highly up-regulated under drought conditions in IAPAR59. This may have been related to the thicker cuticle observed on the abaxial leaf surface in IAPAR59 compared to Rubi. Conclusions The full transcriptome assembly of C. arabica, followed by functional annotation, enabled us to identify differentially expressed genes related to drought conditions. Using these data, candidate genes were selected and their differential expression profiles were confirmed by qPCR experiments in plagiotropic buds of IAPAR59 and Rubi under drought conditions. As regards the genes up-regulated under drought conditions, specifically in the drought-tolerant IAPAR59, several corresponded to orphan genes but also to genes coding proteins involved in signal transduction pathways, as well as ABA and lipid metabolism, for example. The identification of these genes should help advance our understanding of the genetic determinism of drought tolerance in coffee. Electronic supplementary material The online version of this article (doi:10.1186/s12870-016-0777-5) contains supplementary material, which is available to authorized users.

International audience; Pearl millet plays an important role for food security in arid regions of Africa and India. Nevertheless, it is considered an orphan crop as it lags far behind other cereals in terms of genetic improvement efforts. Breeding pearl millet varieties with improved root traits promises to deliver benefits in water and nutrient acquisition. Here, we characterize early pearl millet root system development using several different root phenotyping approaches that include rhizotrons and microCT. We report that early stage pearl millet root system development is characterized by a fast growing primary root that quickly colonizes deeper soil horizons. We also describe root anatomical studies that revealed three distinct types of lateral roots that form on both primary roots and crown roots. Finally, we detected significant variation for two root architectural traits, primary root length and lateral root density, in pearl millet inbred lines. This study provides the basis for subsequent genetic experiments to identify loci associated with interesting early root development traits in this important cereal.

International audience; Knowledge of the cell separation processes underlying organ abscission is limited mainly to the eudicot model systems tomato and Arabidopsis, while less is known about the mechanisms in crop species in general, and monocots in particular. Here we describe a simple phenotypic screen for oil palm plant lines with delayed or non-abscising fruit. The phenotypic test was used on the two species of oil palm including Elaeis guineensis and E. oleifera, in addition to their interspecific hybrids, and hybrids backcrossed to E. guineensis. A large variation in abscission phenotypes was observed. Histological analysis revealed similarities and differences in the abscission zone (AZ) of E. guineensis and E. oleifera, and dominant traits were observed in the AZ of the interspecific crosses. The expression of abscission marker genes for a polygalacturonase (EgPG4) and an ethylene synthesis ACO synthase (EgACO) were monitored during abscission of a randomly selected set of plants and in a non-abscising individual identified by the phenotypic test.

A simple and efficient cryopreservation protocol for coconut zygotic embryos has been developed. Embryos were inoculated in Petri dishes on medium containing 3.2 M glucose, which were placed in hermetically closed containers containing 80 or 160 g silica gel for 48 or 24 h. Moisture content of embryos at the end of this treatment varied between 0.25 and 0.65 g g(-1) DW, depending on the accession. Embryos were then transferred for cryopreservation by rapid immersion of cryotubes in liquid nitrogen. After rapid re-warming, embryos were transferred to culture medium containing Eeuwens mineral elements for germination. This protocol was applied to ten accessions representative of coconut genetic diversity, with germination percentages of cryopreserved embryos between 13.7% and 74.7%.

UMR AGAP - équipe PHIV - Plateforme d'histocytologie et d'imagerie cellulaire végétale; Root and stem rot (RSR) disease caused by Fusariurn oxysporurn f. sp. radicis-vanillae (Forv) is the most damaging disease of vanilla (Vanilla planifolia and V. x tahitensis, Orchidaceae). Breeding programs aimed at developing resistant vanilla varieties are hampered by the scarcity of sources of resistance to RSR and insufficient knowledge about the histopathology of Forv. In this work we have (i) identified new genetic resources resistant to RSR including V planifolia inbreds and vanilla relatives, (ii) thoroughly described the colonization pattern of Forv into selected vanilla accessions, confirming its necrotic non-vascular behavior in roots, and (iii) evidenced the key role played by hypodermis, and particularly lignin deposition onto hypodermal cell walls, for resistance to Forv in two highly resistant vanilla accessions. Two hundred and fifty-four vanilla accessions were evaluated in the field under natural conditions of infection and in controlled conditions using in vitro plants root-dip inoculated by the highly pathogenic isolate Fo072. For the 26 accessions evaluated in both conditions, a high correlation was observed between field evaluation and in vitro assay. The root infection process and plant response of one susceptible and two resistant accessions challenged with Fo072 were studied using wide field and multiphoton microscopy. In susceptible V planifolia, hyphae penetrated directly into the rhizodermis in the hairy root region then invaded the cortex through the passage cells where it induced plasmolysis, but never reached the vascular region. In the case of the resistant accessions, the penetration was stopped at the hypodermal layer. Anatomical and histochemical observations coupled with spectral analysis of the hypodermis suggested the role of lignin deposition in the resistance to Forv. The thickness of lignin constitutively deposited onto outer cell walls of hypodermis was highly correlated with the level of resistance for 21 accessions tested. The accumulation of p-coumaric and sinapic acids, two phenolic precursors of lignin, was observed in the resistant plants inoculated with Fo072, but not in the susceptible one. Altogether, our analyses enlightened the mechanisms at work in RSR resistant genotypes and should enhance the development of novel breeding strategies aimed at improving the genetic control of RSR of vanilla.

Histocytological characteristics of Eucalyptus urophylla 9 Eucalyptus grandis shoot apical meristems (SAMs) were described, comparing five outdoor and in vitro sources of akin genotypes differing in their physiological age. The size and the number of cells of the five zones identified within each SAM, i.e. the two tunica layers (L1 and L2), the central mother cells (CMC), the peripheral zone (PZ) and the combination of these four zones (4CZ) varied according to physiological age and plastochron phase. These five zones were significantly larger with higher numbers of cells for SAMs from mature and juvenile trees than for those from physiologically rejuvenated, in vitro mature and in vitro juvenile plants. However, these origin-related differences were not significant for SAMs in their early plastochron phase, to become obvious in a more advanced plastochron stage. Individual cell and nuclear measurements confirmed the rationale of distinguishing within SAM zones, characterized by specific cell and nuclear sizes liable to vary according to physiological age. The various histocytological investigations carried out established that SAM cell characteristics appeared to be the more reliable indicators of phase change. This was particularly true for the nucleoplasmic ratio and for more qualitative differences observed also at the nuclear level. SAM nuclei of the two in vitro origins were more evenly stained by naphtol blue-black, uniformly light for the juvenile source, whereas the mature source showed also darker nuclei. In contrast, SAM nuclei from outdoor origins had more chromocenters, darker and diffusely spread for the mature source than for the rejuvenated and the juvenile origins, where they were more peripherally distributed and where the nucleoli appeared more clearly. These results were discussed with respect to physiological ageing and in vitro culture influence, and suggest a determining influence of SAM cell nuclei on phase change phenomenon of arborescent species.

DNA methylation was analyzed in Acacia mangium Willd. buds collected from in vitro and field growing shoots from the same clone and its juvenile offspring. Shoot tips from in vitro microshoots showed higher levels of DNA methylation for juvenile (23.4%) than for mature (21.8%) plant material, irrespective of their morphology. Likewise, under the same in vitro conditions, the apical buds collected from microshoots exhibiting the juvenile morphology displayed higher DNA methylation rates (23.2%) than those characterized by the mature phyllode morphological type (22.1%), regardless of the age of the plant material source. In outdoor conditions, apical buds collected from mature tree growing shoots were significantly less methylated (20.9%) than the resting axillary buds located just underneath (25.2%) and than the apical buds from the in vitro microshoots of the same clone and mature-like phyllode morphology (22.6%). Overall, the DNA methylation levels found for our Acacia mangium plant materials were consistent with those reported for other Angiosperms, but showed, similarly to other recent findings in different species, that DNA methylation in plants does not always increase with ageing. This was discussed in relation to other phase-related traits and more particularly foliage characteristics, which are conspicuous markers of ageing in this heteroblastic species.

The current article presents the investigations into the effect of the laurina mutation on the functioning and size of the shoot apical meristem (SAM) in Coffea arabica. This monolocus and Mendelian mutation is known to have pleiotropic effects on tree shape and dwarfism. A comparison between the wild type C. arabica var. Bourbon and its natural dwarf mutant C. arabica var. laurina, also called Bourbon pointu, was carried out leading to three main results: (1) the effects appeared immediately after the emergence of the buttress but did not affect the dome-shaped SAM (size and shape); (2) the effects were located at the peripheral zone and maintained subsequently within the leaf primordia; (3) the effects consisted of reduction in both the size of primordia and the height of incipient internode, consequently resulting in dwarfism of mature leaves and internodes. By contrast, the laurina mutation had no effect on the relationship between the phyllochron and the plastochron, the decussate and opposite phyllotaxis, and the relative timing of SAM functioning within the plastochron.

Plant roots have a large range of functions, including acquisition of water and nutrients, as well as structural support. Dissecting the genetic and molecular mechanisms controlling rice root development is critical for the development of new rice ideotypes that are better adapted to adverse conditions and for the production of sustainably achieved rice yield potential. Most knowledge regarding the gene networks involved in root development has been accumulated in the model dicotyledon plant species Arabidopsis thaliana. Rice, the model monocotyledon species, presents several singularities compared to A. thaliana, including a root architecture characterized by a fibrous root system comprising five types of embryonic and postembryonic roots. The anatomy and morphology of the rice root system, which is typical for a cereal, differs from that of A. thaliana, for instance, by the presence of a lysigenous cortex and additional cell layers compared to the dicotyledon model. Moreover, the structure and functions of the root apical meristem (RAM) of rice are distinct from those of A. thaliana. Recently, several rice root mutants have been identified via forward or reverse genetics, and these will aid in forming hypothesis to characterize either the divergence or conservation of genetic pathways relative to A. thaliana. Furthermore, these mutants will help to identify key genes in rice roots that may be missing in A. thaliana. This review summarizes both classical and recent data concerning the molecular genetics of rice root development, including root anatomy and morphology, RAM structure, RAM patterning, and root mutants.

The effect of growth regulators on induction of androgenesis in coconut was investigated using seven different growth regulators at various concentrations and combinations. Three auxins (1-naphthalene acetic acid-NAA, indoleacetic acid-IAA, picloram) and three cytokinins (2-isopentyl adenine-2-iP, kinetin, zeatin) were tested either alone or in combination with 2,4-dichlorophenoxyacetic acid (2,4-D), using modified Eeuwens Y3 liquid medium as the basal medium. Among the tested auxins, 100 [mu]M NAA in combination with 100 [mu]M 2,4-D enhanced the production of calli/embryos (123) whereas IAA and picloram showed negative and detrimental effects, respectively, for androgenesis induction over 100 lM 2,4- D alone. Kinetin and 2-iP enhanced the production of calli/ embryos when 100 [mu]M 2,4-D was present in the culture medium. Both cytokinins at 10 [mu]M yielded the highest frequencies of embryos (113 and 93, respectively) whereas zeatin (1 or 2.5 [mu]M) had no impact on microspore embryogenesis. When calli/embryos (produced from different treatments in different experiments) were subcultured in somatic embryo induction medium (Y3 medium containing 66 [mu]M 2,4-D), followed by maturation medium (Y3 medium without growth regulators) and germination medium (Y3 medium containing 5 [mu]M-6-benzyladenine- BA and 0.35 [mu]M gibberellic acid-GA3), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%).

Anther culture was used to obtain dihaploid (DH) coconut plants and their ploidy level was determined by flow cytometric analysis. Simple sequence repeat (SSR) marker analysis was conducted to identify the homozygous diploid individuals. Ploidy analysis showed that 50% of the tested plantlets were haploid and 50% were diploid. Polymorphic fragments of the mother palm and their segregation patterns in anther-derived plantlets were used to determine the origin of the diploid plantlets. Using a diagnostic SSR marker (CNZ43), all the diploid plantlets tested were identified as being derived from microspores (i.e. were homozygous) and were thus candidates for use in coconut breeding programs.

UMR DAP, équipe AFEF, Correspondance: costes@supagro.inra.fr Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Genetic control of plant size and shape is a promising perspective, particularly in fruit trees, in order to select desirable genotypes. A recent study on architectural traits in an apple progeny showed that internode length was a highly heritable character. However, few studies have been devoted to internode cellular patterning in dicotyledonous stems, and the interplay between the two elementary cell processes that contribute to their length, i.e. cell division and elongation, is not fully understood. The present study aimed at unravelling their contributions in the genetic variation of internode length in a selection of F(1) and parent genotypes of apple tree, by exploring the number of cells and cell shape within mature internodes belonging to the main axes. The results highlighted that both the variables were homogeneous in samples collected either along a sagital line or along the pith width, and suggest that cell lengthening was homogeneous during internode development. They allowed the total number of cells to be estimated on the internode scale and opened up new perspectives for simplifying tissue sampling procedures for further investigations. Differences in internode length were observed between the genotypes, in particular between the parents, and partly resulted from a compensation between cell number and cell length. However, genetic variations in internode length primarily involved the number of cells, while cell length was more secondary. These results argue for an interplay between cellular and organismal control of internode shape that may involve the rib meristem.