Accumulation of Ascorbic Acid in Tomato Cell Culture: Influence of the Genotype, Source Explant and Time of In Vitro Cultivation.

The production and commercialization of natural antioxidants is gaining increasing importance due to their wide range of biological effects and applications. In vitro cell culture is a valuable source of plant bioactive compounds, especially those highly dependent on environmental factors. Nonetheless, research on the accumulation in plant cultured cells of water-soluble antioxidant vitamins, such as the ascorbic acid (AsA), is very limited. Tomato fruits are a main dietary source of vitamin C and in this work, we explored the potential of in vitro cultured cells for AsA accumulation. Specifically, using a full factorial design, we examined the effect of the source explant, the time in tissue culture and the genetic difference present in two Introgression Line (IL7-3 and IL12-4) that harbor Quantitative Trait Loci (QTLs) for ascorbic acid in fruits. Moreover, we performed an expression analysis of genes involved in AsA metabolism to highlight the molecular mechanisms that can account for the difference between fruit explants and calli. Our work indicated that cultured tomato cells accumulate AsA well beyond the amount present in fruits and that the three factors under investigation and their interaction significantly influence AsA accumulation. The time in tissue culture is the main single factor and, different from the expectations for secondary metabolites, explants from unripe, mature green fruits provided the highest increase in AsA. Moreover, in controlled conditions the genetic differences between the ILs and the control genotype are less relevant for calli cultivated for longer time. Our work showed the potential of tomato cell culture to produce AsA and prompt further refinements towards its possible large-scale exploitation.

Inferring RPW8-NLRs's evolution patterns in seed plants: case study in Vitis vinifera.

MAIN CONCLUSION: Genomic and transcriptomic studies in plants and, more in deep, in grapevine reveal that the disease-resistance RNL gene family is highly variable. RNLs (RPW8-NLRs) are a phylogenetically distinct class of nucleotide oligomerization domain (NOD)-like receptors (NLRs) identified in plants. Two RNLs, namely, the NRG1 (N Requirement Gene 1) and the ADR1 (Activated Disease Resistance 1), have been characterized; however, little is known about the RNL evolutionary history in higher plants. To trace the diversification of RNL gene subfamily, we scanned the NLR proteins of 73 plant genomes belonging to 29 taxa, revealing a noticeable diversification across species and within the same genus or botanic family together with a conspicuous expansion in important crop species. To explore the RNL variability in Vitis vinifera and gain information with respect to their structure, evolutionary diversification of five grape genomes ('Aglianico', 'Falanghina', 'Sultanina', 'Tannat', and 'Nebbiolo') has been compared to the reference genome ('Pinot Noir'). The number of RNLs ranged from 6 ('Sultanina') to 14 ('Nebbiolo'), in contrast to the 10 'Pinot Noir' RNLs. The phylogenetic study on grapevine RNLs revealed that all collapsed into NRG1-clade, rather than four. To investigate more in depth the means of intraspecific variability of grape RNL copies, a transcriptomic profiling in response to powdery mildew (PM) infection was carried out through qRT-PCRs and public databases interrogation. The RNL expression variability identified in transcriptome data sets supports the hypothesis of a functional expansion/contraction in grapevine varieties. Although no direct correlations between grapevine PM-resistance and RNL expression was identified, our work can provide good candidates for functional studies able to elucidate the putative "helper" role of RNLs in grape immune signalling.

Transcriptional Regulation of Ascorbic Acid During Fruit Ripening in Pepper (Capsicum annuum) Varieties with Low and High Antioxidants Content.

Research on plant antioxidants, such as ascorbic acid (AsA) and polyphenols, is of increasing interest in plant science because of the health benefits and preventive role in chronic diseases of these natural compounds. Pepper (Capiscum annuum L.) is a major dietary source of antioxidants, especially AsA. Although considerable advance has been made, our understanding of AsA biosynthesis and its regulation in higher plants is not yet exhaustive. For instance, while it is accepted that AsA content in cells is regulated at different levels (e.g., transcriptional and post-transcriptional), their relative prominence is not fully understood. In this work, we identified and studied two pepper varieties with low and high levels of AsA to shed light on the transcriptional mechanisms that can account for the observed phenotypes. We quantified AsA and polyphenols in leaves and during fruit maturation, and concurrently, we analyzed the transcription of 14 genes involved in AsA biosynthesis, degradation, and recycling. The differential transcriptional analysis indicated that the higher expression of genes involved in AsA accumulation is a likely explanation for the observed differences in fruits. This was also supported by the identification of gene-metabolite relations, which deserve further investigation. Our results provide new insights into AsA differential accumulation in pepper varieties and highlight the phenotypic diversity in local germplasm, a knowledge that may ultimately contribute to the increased level of health-related phytochemicals.

Bioactive Compounds in Brassicaceae Vegetables with a Role in the Prevention of Chronic Diseases.

The beneficial role of the Mediterranean diet in the prevention of chronic diseases, including cardiovascular diseases, diabetes, and obesity, is well-recognized. In this context, Brassicaceae are considered important vegetables due to several evidences of their health promoting effects that are associated to bioactive compounds present in the edible parts of the plants. In this review, the mechanisms of action and the factors regulating the levels of the bioactive compounds in Brassicaceae have been discussed. In addition, the impact of industrial and domestic processing on the amount of these compounds have been considered, in order to identify the best conditions that are able to preserve the functional properties of the Brassicaceae products before consumption. Finally, the main strategies used to increase the content of health-promoting metabolites in Brassica plants through biofortification have been analyzed.

Polyphenol distribution in plant organs of tomato introgression lines.

The content of total polyphenols, chlorogenic, caffeic (CaA) and ferulic acids, and rutin, was investigated in plant organs of three introgression lines (IL7-3, IL10-1 and IL12-4) of Solanum pennellii in Solanum lycopersicum cv M82 and compared with that of cropped parental. Such study aims to evidence factors associated to the introgressions that can affect polyphenol distribution in plant. Among genotypes few differences in polyphenols were recorded on fresh weight basis. IL7-3 showed higher total polyphenols in fruits and lower rutin in leaves than the other genotypes. IL12-4 showed an increasing trend of total polyphenol concentration in fresh vegetative organs; however, this seems to depend on the lower water content rather than on a higher polyphenol biosynthesis in the genotype. IL10-1 sowed higher CaA and lignin contents in leaves. Such differences agree with the morphological and physiological traits of the genotypes.

Histone hyperacetylation affects meiotic recombination and chromosome segregation in Arabidopsis.

In this study, the meiotic role of MEIOTIC CONTROL OF CROSSOVERS1 (MCC1), a GCN5-related histone N-acetyltransferase, is described in Arabidopsis. Analysis of the over-expression mutant obtained by enhancer activation tagging revealed that acetylation of histone H3 increased in male prophase I. MCC1 appeared to be required in meiosis for normal chiasma number and distribution and for chromosome segregation. Overall, elevated MCC1 did not affect crossover number per cell, but has a differential effect on individual chromosomes elevating COs for chromosome 4, in which there is also a shift in chiasma distribution, and reducing COs for chromosome 1 and 2. For the latter there is a loss of the obligate CO/chiasma in 8% of the male meiocytes. The meiotic defects led to abortion in about half of the male and female gametes in the mutant. In wild type, the treatment with trichostatin A, an inhibitor of histone deacetylases, phenocopies MCC1 over-expression in meiosis. Our results provide evidence that histone hyperacetylation has a significant impact on the plant meiosis.

Screening for mutations affecting sexual reproduction after activation tagging in Arabidopsis thaliana.

In this work, a seed-set-based screening was performed on 70 lines of Arabidopsis thaliana after activation tagging mutagenesis to identify mutations in reproductive mechanisms. Five mutants showed significantly lower seed set than the wild type and confirmed the phenotype in the progeny. This phenotype was linked with the marker gene bar carried by T-DNA conferring glufosinate resistance. Genetic analysis revealed that the mutation inheritance was sporophytic in 3 mutants and gametophytic in 2 mutants. In addition, 2 mutants had an extra T-DNA copy. Thus activation tagging can be an effective strategy to identify new mutations affecting sporogenesis or gametogenesis.