Fruit colour and novel mechanisms of genetic regulation of pigment production in tomato fruits

Fruit colour represents a genetic trait with ecological and nutritional value. Plants mainly use colour to attract animals and favour seed dispersion. Thus, in many species, fruit colour coevolved with frugivories and their preferences. Environmental factors, however, represented other adaptive forces and further diversification was driven by domestication. All these factors cooperated in the evolution of tomato fruit, one of the most important in human nutrition. Tomato phylogenetic history showed two main steps in colour evolution: the change from green-chlorophyll to red-carotenoid pericarp, and the loss of the anthocyanic pigmentation. These events likely occurred with the onset of domestication. Then spontaneous mutations repeatedly occurred in carotenoid and phenylpropanoid pathways, leading to colour variants which often were propagated. Introgression breeding further enriched the panel of pigmentation patterns. In recent decades, the genetic determinants underneath tomato colours were identified. Novel evidence indicates that key regulatory and biosynthetic genes undergo mechanisms of gene expression regulation that are much more complex than what was imagined before: post-transcriptional mechanisms, with RNA splicing among the most common, indeed play crucial roles to fine-tune the expression of this trait in fruits and offer new substrate for the rise of genetic variables, thus providing further evolutionary flexibility to the character

Iodine biofortification in tomato

Iodine is an essential element in the human diet, and iodine deficiency is a significant health problem. No attempts to increase iodine content in plant-derived food (biofortification) have so far been particularly effective. We studied iodine uptake in tomato (Solanum lycopersicum L.) to evaluate whether it is possible to increase the iodine concentration in its fruits. Iodine translocation and storage inside tomato tissues were studied using radioactive iodine. Potassium iodide was also supplied at different concentrations to tomato plants to evaluate the resulting iodide concentration both in the vegetative tissues and the fruits. The results indicate that iodine was taken up better when supplied to the roots using hydroponically grown plants. However, a considerable amount of iodine was also stored after leaf treatment, suggesting that iodine transport through phloem also occurred. We found that tomato plants can tolerate high levels of iodine, stored both in the vegetative tissues and fruits at concentrations that are more than sufficient for the human diet. We conclude that tomato is an excellent crop for iodine-biofortification programs

In pursuit of purple: anthocyanin biosynthesis in fruits of the tomato clade

Over the past decade, progress has been made in the characterization of anthocyanin synthesis in fruits of plants belonging to the tomato clade. The genomic elements underlying the activation of the process were identified, providing the basis for understanding how the pathway works in these species. In this review we explore the genetic mechanisms that have been characterized to date, and detail the various wild relatives of the tomato, which have been crucial for recovering ancestral traits that were probably lost during evolution from green-purple to yellow and red tomatoes. This knowledge should help developing strategies to further enhance the status of the commercial tomato lines on sale, based on both genome editing and breeding techniques

Iodine fortification plant screening process and accumulation in tomato fruits and potato Tubers

Iodine is an essential microelement for human health, and Recommended Daily Allowance (RDA) of such element should range from 40 to 200 \ub5g day-1. Because of the low iodine contents in vegetables, cereals, and many other foods, Iodine Deficiency Disorder (IDD) is one of the most widespread nutrient deficiency diseases in the world. Therefore, investigations of iodine uptake in plants with the aim of their fortification can help reaching the important health and social objective of IDD elimination. This study was conducted to determine the effects of the absorption of iodine from two different chemical forms - potassium iodide (I-) vs. potassium iodate (IO-3) - in a wide range of wild and cultivated plant species. Pot plants were irrigated with different concentrations of I- or IO-3, namely 0.05% and 0.1% (w/v) I-, and 0.05%, 0.1%, 0.2% and 0.5% (w/v) IO-3. Inhibiting effects on plant growth were observed after adding these amounts of iodine to the irrigation water. Plants wereable to tolerate better the higher levels of iodine as IO-3 rather than I- in the root environment. Among cultivated species, barley (Hordeum vulgare L.) showed the lowest, and maize (Zea mays L.) together with tobacco (Nicotiana tabacum L.) the highest biomass reductions due to iodine toxicity. After the screening, cultivated tomato and potato resulted good targets for a fortification rate study among the species screened. When fed with 0.05% iodine salts, potato (Solanum tuberosum L.) tubers and tomato (Solanum lycopersicum L.) fruits absorbed iodine up to 272 and 527 \ub5g/100 g FW from IO-3, and 1,875 and 3,900 \ub5g/100 g FW from I-. These uptake levels were well above the RDA of 150\ub5g day-1 for adults. Moreover, the agronomic efficiency of iodine accumulation of potato tubers and tomato fruits was calculated. Both plant organs showed greater accumulation efficiency for given unit of iodine from iodide than from iodate. This accumulation efficiency decreased in both potato tubers and tomato fruits at iodine concentrations higher than 0.05% for iodide, and at respectively 0.2% and 0.1% for iodate. On the basis of the uptake curve it was finally possible to calculate, although to be validated, the doses of supply in the irrigation water of iodine as iodate (0.028% for potato, and0.014% for tomato) as well as of iodide (0.004% for potato, and 0.002% for tomato), to reach the 150 \ub5g day-1 RDA for adults in 100 g of such vegetables, to efficiently control IDD

A reassessment of the role of sucrose synthase in the hypoxic sucrose‐ethanol transition in Arabidopsis

Plants under low-oxygen availability adapt their metabolism to compensate for the lower ATP production that arises from the limited respiratory activity in mitochondria. Anaerobic glycolysis requires continuous fuelling of carbon units, also provided from sucrose. The anaerobic catabolism of sucrose is thought to require the activity of sucrose synthase, being this enzymatic reaction more energetically favourable than that of invertase. The role of sucrose synthases (SUS) for aerobic sucrose catabolism in Arabidopsis has been recently questioned since SUS mutants fail to show altered phenotype or metabolic profile. In the present paper, we analysed the role of SUS1 and SUS4, both induced by low oxygen, in plant survival and ethanol production. The results showed that mutants lacking both SUS were as tolerant to low oxygen as the wild type in most of the experimental conditions tested. Only under conditions of limiting sugar availability the requirement of SUS1 and SUS4 for ethanol production was evident, although partly compensated by invertase activities, as revealed by the use of a double mutant lacking the two major cytosolic invertases. We conclude that, contrary to general belief, the sucrose synthase pathway is not the preferential route for sucrose metabolism under hypoxia