Rebecca Stevens

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Génétique et Amélioration des Fruits et Légumes (GAFL)

The French National Research Institute for Agriculture, Food and the Environment (INRAE) conserves and distributes five vegetable collections as seeds: the aubergine* (in this article the word aubergine refers to eggplant), pepper, tomato, melon and lettuce collections, together with their wild or cultivated relatives, are conserved in Avignon, Fra...

Plant central metabolism generates reactive oxygen species (ROS), which are key regulators that mediate signalling pathways involved in developmental processes and plant responses to environmental fluctuations. These highly reactive metabolites can lead to cellular damage when the reduction-oxidation (redox) homeostasis becomes unbalanced. Whilst d...

Most traits showed signifcant genetic variations: extreme root apical diameters, inter-branch distances, and slopes of the regression lines of elongation rate versus apical diameter. On all genotypes, the initial root system issued from the elongation and branching of the taproot was complemented 2-3 weeks later by the emergence of a set of adventi...

Ascorbic acid is considered to be one of the most important antioxidants in plants and plays a vital role in the adaptation of plants to unfavorable conditions. In the present study, an ascorbate oxidase gene (Solyc04g054690) was over-expressed in cherry tomato cv. West Virginia 106 lines and compared with previously studied RNAi silenced ascorbate...

em>Background : We investigated root architecture and plant biomass traits of 25 aubergine genepool accessions representative of 9 Solanum L. species, including S. melongena L., grown at two sites in South-East France in order to quantify the diversity of root phenotypes, identify correlations between traits and determine the influence of the envir...

We aimed to examine the response of three tomato introgression lines (IL925.3, IL925.5 and IL925.6) to NaCl stress. These lines originated from a cross between M82 (Solanum lycopersicum) and the wild salttolerant tomato Solanum pennellii, each line containing a different fragment of the S.pennellii genome. Salt-sensitive phenotypes related to plant...

The use of saline water for plant production will become increasingly necessary over future decades. In some cases, fruit quality such as in tomato, can be improved by irrigation with saline water. The influence of different salt concentrations on physiological responses and the expression of some selected genes of cherry tomato (Solanum lycopersic...

Heatmap showing protein levels in pericarp of fruit 20 days after anthesis (3 pools of 30 fruits) of the transgenic lines and wild-type. All proteins were separated by two-dimensional gel electrophoresis and identified by mass spectrometry. The log2 of the protein ratio with the wild-type for each transgenic line is presented. The scale goes from g...

Gene expression profiles for AO, Solyc04g054690; GLD, Solyc10g079470 and MDHAR, Solyc09g009390 as obtained from the TomExpress tool (http://tomexpress.toulouse.inra.fr).

Fruit metabolite data (orange fruit pericarp). Quantitative data for the following metabolites: galactose, mannose, glutamate, glutamine, alanine, aspartate, tyrosine, fructose, glucose, sucrose, ascorbate, dehydroascorbate, GABA, citramalate, citrate, malate, chlorogenic acid, caffeic acid glucoside, cis-chlorogenic acid, quercetin derivative, and...

WGCNA module identification. A graphical representation of the data from Supplementary Table S4: module eigengenes are labeled by color and the module membership scale from red (high adjacency, positive correlation) to green (low adjacency, negative correlation) shown for each metabolite and protein. The 7633 genes were used to generate the topolog...

Proteins. Raw data for quantifiable proteins (see Materials and methods) from orange pericarp with spot identifier code for each of the three pools for the wild type, AO, GLD, and MDHAR RNAi lines.

Gene expression profiles for AO, Solyc04g054690; GLD, Solyc10g079470 and MDHAR, Solyc09g009390 as obtained from the Solgenomics expression atlas tool (http://tea.solgenomics.net).

Ascorbate and dehydroascorbate levels in pericarp fruit 20 days after anthesis of transgenic lines and WT. Ascorbate and dehydroascorbate were assayed in the pericarp tissue (3 biological replicates of 30 fruits per pool) of the lines by a spectrophotometric method. Measurements show means with standard error (SE). A comparison of means was carried...

WGCNA. Solyc identifier, gene function, GO terms, module color, module membership (MM or eigengene-based connectivity) and associated p-value for the 38 modules and 7633 genes as generated by the WGCNA R package.

Transcriptome raw data. For each of the 7633 genes mean expression (normalized) in each of the three transgenic lines and wild type with standard error (SE). F values, p-values, false discovery rate corrected p-values and fold change (FC) are also given for each comparison as follows: 1: AO vs. WT, 2: GLD vs. WT, 3: MDHAR vs. WT, 4: AO vs. MDHAR, 5...

Changing the balance between ascorbate, monodehydroascorbate, and dehydroascorbate in plant cells by manipulating the activity of enzymes involved in ascorbate synthesis or recycling of oxidized and reduced forms leads to multiple phenotypes. A systems biology approach including network analysis of the transcriptome, proteome and metabolites of RNA...

Ascorbate redox metabolism and growth have been shown to be linked and related to the activity of enzymes that produce or remove the radical monodehydroascorbate, the semi-oxidized form of ascorbate (ascorbate oxidase or peroxidase and monodehydroascorbate reductase respectively). Previous work in cherry tomato has revealed correlations between mon...

Ascorbate content in plants is controlled by its synthesis from carbohydrates, recycling of the oxidized forms and degradation. Of these pathways, ascorbate degradation is the least studied and represents a lack of knowledge which could impair improvement of ascorbate content in fruits and vegetables as degradation is non-reversible and leads to a...

Ascorbate oxidase (AO) is a member of the multi-copper oxidase family of enzymes and converts ascorbate to monodehydroascorbate at the same time as reducing oxygen to water. The enzyme is present in the apoplastic space of plant cells and seems to be particularly highly expressed in roots and fruits of the Cucurbitaceae family. Cell expansion and d...

Ascorbate oxidase (AO) is a member of the multi-copper oxidase family of enzymes and converts ascorbate to monodehydroascorbate at the same time as reducing oxygen to water. The enzyme is present in the apoplastic space of plant cells and seems to be particularly highly expressed in roots and fruits of the Cucurbitaceae family. Cell expansion and d...

GDP-D-mannose epimerase (GME, EC 5.1.3.18) converts GDP-D-mannose to GDP-L-galactose, and is considered to be a central enzyme connecting the major ascorbate biosynthesis pathway to primary cell wall metabolism in higher plants. Our previous work demonstrated that GME is crucial for both ascorbate and cell wall biosynthesis in tomato. The aim of th...

Ascorbate is oxidized into the radical monodehydroascorbate (MDHA) through ascorbate oxidase or peroxidase activity or non-enzymatically by reactive oxygen species. Regeneration of ascorbate from MDHA is ensured by the enzyme monodehydroascorbate reductase (MDHAR). Previous work has shown that growth processes and yield can be altered by modifying...

Tomato is an important crop worldwide and one of the major sources of vitamin C (ascorbate) in the human diet. Ascorbate contributes both to tomato nutritional quality and has roles in stress tolerance and adaptation to the environment. In this study we show the variability that exists in tomato germplasm in terms of ascorbate content (10 to 90 mg/...

Genome-wide association studies have been successful in identifying genes involved in polygenic traits and are valuable for crop improvement. Tomato (Solanum lycopersicum) is a major crop and is highly appreciated worldwide for its health value. We used a core collection of 163 tomato accessions composed of S. lycopersicum, S. lycopersicum cv. cera...

Understanding how the fruit microclimate affects ascorbate (AsA) biosynthesis, oxidation and recycling is a great challenge in improving fruit nutritional quality. For this purpose, tomatoes at breaker stage were harvested and placed in controlled environment conditions at different temperatures (12, 17, 23, 27 and 31°C) and irradiance regimes (dar...

Fruit antioxidants are necessary for human health and also have physiological roles in protecting fruit against oxidative stress. Our previous work has shown that monodehydroascorbate reductase (MDHAR) activity was positively correlated with fruit resistance to cold storage in introgression lines of tomato, Solanum lycopersicum. We have produced tr...

To understand how light and temperature may affect fruit ascorbate (AsA) content, tomato fruit harvested at breaker stage were placed under different temperatures (12, 23 and 31EC) and irradiance regimes (darkness or 150 μmol m!2 s!1). After 56h, fruit were cut and pericarps were frozen and ground in liquid nitrogen. Changes in AsA metabolism were...

Ascorbate is a powerful antioxidant in plants. Ascorbate concentration depends on its biosynthesis, recycling and degradation; these are under genetic control and closely related to environmental conditions. Ascorbate recycling, controlled by the enzymes monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), ensures a high-ra...

Ascorbate is a powerful antioxidant in plants, and its levels are an important quality criteria in commercial species. Factors influencing these levels include environmental variations, particularly light, and the genetic control of its biosynthesis, recycling and degradation. One of the genes involved in the recycling pathway encodes a monodehydro...

Ascorbate is a widespread and efficient antioxidant that has multiple functions in plants, traditionally associated with the reactions of photosynthesis. This review aims to look at ascorbate from an evolutionary perspective. Cyanobacteria, algae, and bryophytes contain lower concentrations of ascorbate than higher plants, where the molecule accumu...

Background / Purpose: Genome-wide association studies (GWAS) have been successful in identifying genes involved in polygenic traits, notably those associated with crop improvement. We propose applying a recently developed multi-locus mixed model in a major crop, such as the tomato, as a general method for mapping complex traits in structured popu...

The regulation of carbon allocation between photosynthetic source leaves and sink tissues in response to stress is an important factor controlling plant yield. Ascorbate oxidase is an apoplastic enzyme, which controls the redox state of the apoplastic ascorbate pool. RNA interference was used to decrease ascorbate oxidase activity in tomato (Solanu...

Tomato is an important crop worldwide and one of the major sources of vitamin C (ascorbate) in the human diet. Ascorbate contributes both to tomato nutritional quality and has roles in stress tolerance and adaptation to the environment. In this study we show the variability that exists in tomato germplasm in terms of ascorbate content (10 to 90 mg/...

Little is known about the light regulation of vitamin C synthesis in fruits. In contrast, previous studies in leaves revealed that VTC2 (coding for GDP-L: -galactose phosphorylase) was one of the key genes up-regulated by light in leaves. Our objective was to determine how the expression of ascorbate (AsA) synthesis genes in tomato (Solanum lycoper...

The present study aimed to clarify the relationship between sugars and vitamin C in fruit. The objective was to determine whether vitamin C content was regulated by sugar content due to the role of sugar as a precursor for vitamin C. During summer, maximal content in sugar and vitamin C were found in both genotypes tested Solanum lycopersicon 'Cerv...

Antioxidant systems play an important role in prevention of chilling injury, and chilling-tolerant fruit may initially contain more antioxidants or be able to maintain their antioxidant levels during stress. Tomato fruit are chilling sensitive and chilling symptoms generally appear after fruit are transferred to non chilling temperatures. The aim o...

Very few reports have studied the interactions between ascorbate and fruit metabolism. In order to get insights into the complex relationships between ascorbate biosynthesis/recycling and other metabolic pathways in the fruit, we undertook a fruit systems biology approach. To this end, we have produced tomato transgenic lines altered in ascorbate c...

Vitamin C levels in tomato contribute to their nutritional value, but this antioxidant also seems to play a role on fruit quality. The aim of this study was to investigate the effect of improving Results Materials & Methods M82 fruits presented higher firmness loss than IL9.2.5 and typical chilling injury phenotype. These defaults increased with th...

The GDP-D-mannose 3,5-epimerase (GME, EC 5.1.3.18), which converts GDP-d-mannose to GDP-l-galactose, is generally considered to be a central enzyme of the major ascorbate biosynthesis pathway in higher plants, but experimental evidence for its role in planta is lacking. Using transgenic tomato lines that were RNAi-silenced for GME, we confirmed tha...

The mechanisms involving light control of vitamin C content in fruits are not yet fully understood. The present study aimed to evaluate the impact of fruit and leaf shading on ascorbate (AsA) accumulation in tomato fruit and to determine how fruit sugar content (as an AsA precursor) affected AsA content. Cherry tomato plants were grown in a glassho...

Quantitative trait loci (QTL) mapping is a step towards the identification of factors regulating traits such as fruit ascorbic acid content. A previously identified QTL controlling variations in tomato fruit ascorbic acid has been fine mapped and reveals that the QTL has a polygenic and epistatic architecture. A monodehydroascorbate reductase (MDHA...

The initiation of meiotic recombination by the formation of DNA double-strand breaks (DSBs) catalysed by the Spo11 protein is strongly evolutionary conserved. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation, but, unlike Spo11, few of these proteins seem to be conserved across kingdoms. In order to investiga...

Fresh fruit and vegetables are a major source of ascorbic acid (vitamin C), an important antioxidant for the human diet and also for plants. Ascorbic acid content in fruit exhibits a quantitative inheritance. Quantitative trait loci (QTL) for ascorbic acid content have been mapped in three tomato populations derived from crosses between cultivated...

We present a technique for easy, rapid analysis of both total and reduced forms of vitamin C in fruits using microplates and a plate reader. This technique has been compared with a spectrofluorometric technique classically used for assaying vitamin C in fresh tomato. We have applied these methods to a population of 118 tomato mutant lines and contr...

CDC45 is required for the initiation of DNA replication in yeast and cell proliferation in mammals and functions as a DNA polymerase alpha loading factor in Xenopus. We have cloned a CDC45 homolog from Arabidopsis whose expression is upregulated at the G1/S transition and in young meiotic flower buds. One-third of Arabidopsis 35S:CDC45 T1 RNA inter...

The precise control of cell cycle progression is critical for coherent development. In all eukaryotes, the cell cycle is controlled by complexes composed of a cyclin-dependent kinase (CDK) and a cyclin. CDK activity is controlled at multiple levels, including association with CDK inhibitory proteins called CKIs. Here, we report the isolation and ch...

The commitment to DNA replication is a key step in cell division control. The Arabidopsis MCM3 homologue forms part of the mini chromosome maintenance (MCM) complex involved in the initiation of DNA replication at the transition G1/S. Consistent with its role at the G1/S transition we show that the AtMCM3 gene is transcriptionally regulated at S ph...

The E2F transcription factors are key components of the cyclin D/retinoblastoma/E2F pathway. Here we demonstrate that Arabidopsis thaliana contains six functional AtE2F genes that are all expressed in cell suspension culture but show different patterns of expression during cell cycle progression. According to their structural and functional feature...

In eukaryotes, transcription factors of the E2F family, in addition to having a role in cell proliferation, participate in regulating apoptosis, differentiation and development. In Arabidopsis thaliana, eight gene sequences have been identified as encoding E2F or DP homologues. DP proteins form heterodimers with E2Fs. The aim of this work was to ch...

 Expression in transgenic tobacco (Nicotiana tabacum L.) of a pea (Pisum sativum L.) GOR2 cDNA, encoding an isoform of glutathione reductase (GOR2), resulted in a 3- to 7-fold elevation of total foliar glutathione reductase (GR) activity. The enzyme encoded by GOR2 was confirmed to be extraplastidial in organelle fractionation studies and was consi...

A second glutathione reductase (GR) cDNA has been cloned and sequenced from pea (Pisum sativum L. cv. Birte). This new GR cDNA (GOR2) does not encode a preprotein with a transit peptide and therefore is most likely to represent a cytosolic GR. It is significantly different at the DNA level from the previously cloned chloroplastidial/mitochondrial p...

There is clear potential for the genetic manipulation of key enzymes involved in stress metabolism in transgenic plants. However, the data emerging so far from such experiments are equivocal. The detailed analysis of stress responses in progeny of primary transgenics, coupled with comparisons with control transgenic plants that do not contain the G...