Cryopreservation of ex-vitro-grown Rosa chinensis 'Old Blush' buds using droplet-vitrification and encapsulation-dehydration

Axillary buds from greenhouse-grown plants of Rosa chinensis 'Old Blush' were successfully used to establish cryopreservation protocols using both droplet-vitrification and encapsulation-dehydration methods. In droplet vitrification, regrowth occurred after exposure to liquid nitrogen even without pre-culture in the loading solution (LS) before immersion in the plant vitrification solution 2 (PVS2). However, a 20-80 min LS step followed by a short immersion in PVS2 for 3 or 15 min, at 0 A degrees C gave the best regrowth rates (82-86 %). In encapsulation dehydration, the level of dehydration significantly influenced shoot regrowth. The best regrowth rate, 60 %, was obtained at a bead water content of 0.35 g water per g dry weight. These results demonstrate the possibility of using greenhouse plants of rose for cryopreservation by droplet vitrification and encapsulation dehydration

The PUF Protein Family: Overview on PUF RNA Targets, Biological Functions, and Post Transcriptional Regulation

Post-transcriptional regulation of gene expression plays a crucial role in many processes. In cells, it is mediated by diverse RNA-binding proteins. These proteins can influence mRNA stability, translation, and localization. The PUF protein family (Pumilio and FBF) is composed of RNA-binding proteins highly conserved among most eukaryotic organisms. Previous investigations indicated that they could be involved in many processes by binding corresponding motifs in the 3UTR or by interacting with other proteins. To date, most of the investigations on PUF proteins have been focused on Caenorhabditis elegans, Drosophila melanogaster, and Saccharomyces cerevisiae, while only a few have been conducted on Arabidopsis thaliana. The present article provides an overview of the PUF protein family. It addresses their RNA-binding motifs, biological functions, and post-transcriptional control mechanisms in Caenorhabditis elegans, Drosophila melanogaster, Saccharomyces cerevisiae, and Arabidopsis thaliana. These items of knowledge open onto new investigations into the relevance of PUF proteins in specific plant developmental processes

Exploring plant defense pathways in the carrot-Alternaria dauci pathosystem, a non-model interaction

Communication (Communication avec actes dans un congrès)Most of the molecular mechanisms underlying plant partial resistance QTLs are still unknown. Twocompeting hypothesis are generally invoked to link observed field resistance with actual moleculargene function. An older hypothesis links partial resistance QTLs with overcome typical R genesencoding classical NBS-LRR or LRR-TM type proteins. In a recent paper (Hu et al., 2008), partial plantresistance was linked with defense mechanisms. These results led us to develop a candidate geneapproach to study partial plant resistance of carrot (Daucus carota) towards its main foliar fungalpathogen, Alternaria dauci. Since carrot is a non-model plant, little sequence data is available onpublic databases. We thus chose to develop a homology-based cloning strategy in order to detectand sequence defense-related genes in carrot. Since A. dauci is a necrotrophic pathogen, we focusedthis strategy on Jasmonic acid (JA) signaling pathway and JA controlled defense genes (such as JAZ3or PR4). Since the degenerate primer strategy is not known to be effective on each and every gene,we chose to apply it in a parallel fashion on a rather large set of genes. Alignments of sequence datafrom eight already sequenced dicotyledonous plant species were performed for 15 genes.Degenerate primers were defined for 10 genes involved in this JA pathway. Additionally, we defineddegenerate primers for two defense genes that are not mainly JA- regulated: the SA-regulateddefense gene PR1, and the non host defense gene PAL1. Five out of 12 genes were partially clonedand sequenced. Two strategies are currently deployed to link these defense related genes withpartial resistance QTLs observed in the carrot-A. dauci interaction (Le Clerc et al., 2009). SNPs arebeing found between the resistant and susceptible parents of our mapping populations. They willhelp us to find potential QTL-candidate co-localizations. Absence of such a co-localization does notmean that a potential candidate is not involved in defense. It is also possible that the QTL influencesdefense-related genes activation rather than the efficiency of the cognate PR proteins. For thisreason, we also plan to study the induction of these genes by A. dauci in both susceptible andresistant backgrounds.</p

The Sugar-Signaling Hub: Overview of Regulators and Interaction with the Hormonal and Metabolic Network

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future

Antagonistic Effect of Sucrose Availability and Auxin on Rosa Axillary Bud Metabolism and Signaling, Based on the Transcriptomics and Metabolomics Analysis

International audienceShoot branching is crucial for successful plant development and plant response to environmental factors. Extensive investigations have revealed the involvement of an intricate regulatory network including hormones and sugars. Recent studies have demonstrated that two major systemic regulators-auxin and sugar-antagonistically regulate plant branching. However, little is known regarding the molecular mechanisms involved in this crosstalk. We carried out two complementary untargeted approaches-RNA-seq and metabolomics-on explant stem buds fed with different concentrations of auxin and sucrose resulting in dormant and non-dormant buds. Buds responded to the combined effect of auxin and sugar by massive reprogramming of the transcriptome and metabolome. The antagonistic effect of sucrose and auxin targeted several important physiological processes, including sink strength, the amino acid metabolism, the sulfate metabolism, ribosome biogenesis, the nucleic acid metabolism, and phytohormone signaling. Further experiments revealed a role of the TOR-kinase signaling pathway in bud outgrowth through at least downregulation of Rosa hybrida BRANCHED1 (RhBRC1). These new findings represent a cornerstone to further investigate the diverse molecular mechanisms that drive the integration of endogenous factors during shoot branching

Effects of carbohydrate sources and BAP concentrations on In vitro morphogenesis of four rose genotypes

International audienceRoses are known to be recalcitrant to in vitro regeneration methods. Regeneration via de novo shoot organogenesis or somatic embryogenesis is the key step for the successful process of genetic transformation and functional validation of genes. To improve the de novo shoot organogenesis process in rose genotypes, it is essential to control the physiological state of donor plants in order to prepare explant tissues and increase their regeneration abilities. Therefore, the aim of this study was to improve donor plant in vitro culture and mainly: (1) to understand the effect of media composition, including cytokinin and carbohydrate sources on cultured node morphogenesis, (2) to verify a possible interaction between genotype and media content and (3) to evaluate the best composition of the medium for a long in vitro storage to manage collections by increasing subculture period of four donor plant rose genotypes. All genotypes were able to increase their multiplication rate when they were subcultured on medium supplemented with benzylaminopurine, (BAP) 3 mg/L and high concentration of carbohydrate except sorbitol. Fructose or glucose was the best carbohydrate sources for multiplication but the optimal dose depends on genotype. The maximum of shoot elongation was obtained on medium including 0.5 mg/L benzylaminopurine and 0.1 mg/L gibberellic acid supplemented with 30 g/L fructose or glucose. Callus formation and rooting were enhanced by high concentration of fructose, glucose or sucrose. Maltose and sorbitol allowed an extended storage time for all genotypes. On the other hand, leaf explants issued from medium containing high concentration of benzylaminopurine and lacking gibberellic acid were able to regenerate adventitious shoot after transfer on shoot regeneration medium if combined with the optimal carbohydrate type and concentration which allow multiplication for the mother plants

Effects of carbohydrate source and BAP concentration on in vitro morphogenesis of four Rose genotypes

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Carotenoid Content and Root Color of Cultivated Carrot: A Candidate-Gene Association Study Using an Original Broad Unstructured Population

Article de revue (Article scientifique dans une revue à comité de lecture)International audienceAccumulated in large amounts in carrot, carotenoids are an important product qualityattribute and therefore a major breeding trait. However, the knowledge of carotenoid accumulationgenetic control in this root vegetable is still limited. In order to identify the geneticvariants linked to this character, we performed an association mapping study with a candidategene approach.We developed an original unstructured population with a broad geneticbasis to avoid the pitfall of false positive detection due to population stratification. Wegenotyped 109 SNPs located in 17 candidate genes – mostly carotenoid biosynthesisgenes – on 380 individuals, and tested the association with carotenoid contents and colorcomponents. Total carotenoids and β-carotene contents were significantly associated withgenes zeaxanthin epoxydase (ZEP), phytoene desaturase (PDS) and carotenoid isomerase(CRTISO) while α-carotene was associated with CRTISO and plastid terminal oxidase(PTOX) genes. Color components were associated most significantly with ZEP. Our resultssuggest the involvement of the couple PDS/PTOX and ZEP in carotenoid accumulation, asthe result of the metabolic and catabolic activities respectively. This study brings new insightsin the understanding of the carotenoid pathway in non-photosynthetic organs.</p