Explore the vast range of titles available.

Nutrition recommendations worldwide emphasize ingestion of plant-based diets rather than diets that rely primarily on animal products. However, this plant-based diet could limit the intake of essential nutrients such as calcium. Osteoporosis is one of the world's most prevalent nutritional disorders, and inadequate dietary calcium is a known contributor to the pathophysiology of this condition. Previously, we have modified carrots to express increased levels of a plant calcium transporter (sCAX1), and these plants contain [almost equal to]2-fold-higher calcium content in the edible portions of the carrots. However, it was unproven whether this change would increase the total amount of bioavailable calcium. In randomized trials, we labeled these modified carrots with isotopic calcium and fed them to mice and humans to assess calcium bioavailability. In mice feeding regimes (n = 120), we measured ⁴⁵Ca incorporation into bones and determined that mice required twice the serving size of control carrots to obtain the calcium found in sCAX1 carrots. We used a dual-stable isotope method with ⁴²Ca-labeled carrots and i.v. ⁴⁶Ca to determine the absorption of calcium from these carrots in humans. In a cross-over study of 15 male and 15 female adults, we found that when people were fed sCAX1 and control carrots, total calcium absorption per 100 g of carrots was 41% ± 2% higher in sCAX1 carrots. Both the mice and human feeding studies demonstrate increased calcium absorption from sCAX1-expressing carrots compared with controls. These results demonstrate an alternative means of fortifying vegetables with bioavailable calcium.

The kinetics of anthocyanin metabolism was investigated in a human feeding trial. Volunteers (n 12) consumed purple carrots containing five anthocyanin forms: cyanidin-3-(xylose-glucose-galactoside), cyanidin-3-(xylose-galactoside), cyanidin-3-(xylose-sinapoyl-glucose-galactoside), cyanidin-3-(xylose-feruloyl-glucose-galactoside) and cyanidin-3-(xylose-coumuroyl-glucose-galactoside). The purple carrots were served as three different treatments in a crossover design with a 3-week washout between treatments. Purple carrot treatments were 250 g raw carrots, 250 g cooked carrots and 500 g cooked carrots. Serial blood and urine samples were collected for 8 and 24 h after the dose, respectively, and analysed for anthocyanins. Of the anthocyanin forms ingested, four were detected in plasma and urine: cyanidin-3-(xylose-glucose-galactoside), cyanidin-3-(xylose-galactoside), cyanidin-3-(xylose-sinapoyl-glucose-galactoside) and cyanidin-3-(xylose-feruloyl-glucose-galactoside). The time courses of plasma and urine anthocyanin contents were evaluated with compartmental modelling. Results showed that absorption, gastrointestinal transit and plasma elimination are dependent on anthocyanin structure. Absorption efficiencies of acylated compounds (cyanidin-3-(xylose-sinapoyl-glucose-galactoside) and cyanidin-3-(xylose-feruloyl-glucose-galactoside)) were less than those for non-acylated anthocyanins (cyanidin-3-(xylose-glucose-galactoside) and cyanidin-3-(xylose-galactoside)). The acylated anthocyanins exhibited a shorter half-life for gastrointestinal absorption than the non-acylated anthocyanins. Fractional elimination of non-acylated compounds was slower than that for acylated anthocyanins. These results provide the first information about the kinetics of individual anthocyanins in human beings.

We report a chromosome-scale assembly and analysis of the Daucus carota genome, an important source of provitamin A in the human diet and the first sequenced genome among members of the Euasterid II clade. We characterized two new polyploidization events, both occurring after the divergence of carrot from members of the Euasterid I clade, clarifying the evolutionary scenario before and after the radiation of the two main Asterid clades. Large- and small-scale lineage-specific duplications contributed to the expansion of gene families including those with roles in flowering time, defense response, flavor, and pigment accumulation. We demonstrated that the primary genetic locus underlying carotenoid accumulation in the carrot root, that is the foundation of the orange color of modern carrots, is not directly controlled at the biosynthetic level. A candidate gene was identified, and transcriptome data suggested that high carotenoid accumulation involves overexpression of several light-induced genes operating in photosystem development and function. These results provide a resource for crop improvement, for comparative genome analysis in the Asterid lineage, and for the discovery of novel genetic mechanisms regulating carotene biosynthesis and accumulation in plants.

Arbuscular mycorrhizal (AM) fungi facilitate plant uptake of mineral nutrients and draw organic nutrients fromthe plant. Organic nutrients are thought to be supplied primarily in the formof sugars. Here we show that the AM fungus Rhizophagus irregularis is a fatty acid auxotroph and that fatty acids synthesized in the host plants are transferred to the fungus to sustain mycorrhizal colonization. The transfer is dependent on RAM2 (REQUIRED FOR ARBUSCULAR MYCORRHIZATION 2) and the ATP binding cassette transporter–mediated plant lipid export pathway. We further show that plant fatty acids can be transferred to the pathogenic fungus Golovinomyces cichoracerum and are required for colonization by pathogens. We suggest that themutualistic mycorrhizal and pathogenic fungi similarly recruit the fatty acid biosynthesis program to facilitate host invasion.

The original domesticated carrots (Daucus carota) are thought to have been purple, accumulating large quantities of anthocyanins in their roots. A quantitative trait locus associated with anthocyanin pigmentation in purple carrot roots has been identified on chromosome 3 and includes two candidate genes, DcMYB6 and DcMYB7. Here, we characterized the functions of DcMYB6 and DcMYB7 in carrots. Overexpression of DcMYB7, but not DcMYB6, in the orange carrot 'Kurodagosun' led to anthocyanin accumulation in roots. Knockout of DcMYB7 in the solid purple (purple periderm, phloem, and xylem) carrot 'Deep Purple' using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 system resulted in carrots with yellow roots. DcMYB7 could activate the expression of its DcbHLH3 partner, a homolog of the anthocyanin-related apple (Malus × domestica) bHLH3, and structural genes in the anthocyanin biosynthetic pathway. We determined that the promoter sequence of DcMYB7 in nonpurple carrots was interrupted either by DcMYB8, a nonfunctional tandem duplication of DcMYB7, or by two transposons, leading to the transcriptional inactivation of DcMYB7 in nonpurple carrot roots. As a result, nonpurple carrots fail to accumulate anthocyanins in their roots. Our study supports the hypothesis that another genetic factor suppresses DcMYB7 expression in the phloem and xylem of purple peridermal carrot root tissues. DcMYB7 also regulated the glycosylation and acylation of anthocyanins by directly activating DcUCGXT1 and DcSAT1. We reveal the genetic factors conditioning anthocyanin pigmentation in purple versus nonpurple carrot roots. Our results also provide insights into the mechanisms underlying anthocyanin glycosylation and acylation.

Background Gibberellins stimulate cell elongation and expansion during plant growth and development. Carrot is a root plant with great value and undergoes obvious alteration in organ size over the period of plant growth. However, the roles of gibberellins in carrot remain unclear. Results To investigate the effects of gibberelliins on the growth of carrot, we treated carrot plants with gibberellic acid 3 (GA 3 ) or paclobutrazol (a gibberellin inhibitor). The results found that GA 3 dramatically reduced the root growth but stimulated the shoot growth of carrot. It also significantly promoted xylem development in the tuberous root of carrot. In addition, transcript levels of genes related to gibberellins, auxin, cytokinins, abscisic acid and brassinolides were altered in response to increased or reduced gibberellins. Conclusions The inhibited tuberous root growth but enhanced shoot growth in plants treated with GA 3 can be principally attributed to the changes in the xylem development of carrot roots. Negative feedback regulation mechanism of gibberellin biosynthesis also occurred in response to altered gibberellin accumulation. Gibberellins may interact with other hormones to regulate carrot plant growth through crosstalk mechanisms. This study provided novel insights into the functions of gibberellins in the growth and development of carrot.

Arbuscular mycorrhiza (AM) is a root endosymbiosis between plants and glomeromycete fungi. It is the most widespread terrestrial plant symbiosis, improving plant uptake of water and mineral nutrients. Yet, despite its crucial role in land ecosystems, molecular mechanisms leading to its formation are just beginning to be unravelled. Recent evidence suggests that AM fungi produce diffusible symbiotic signals. Here we show that Glomus intraradices secretes symbiotic signals that are a mixture of sulphated and non-sulphated simple lipochitooligosaccharides (LCOs), which stimulate formation of AM in plant species of diverse families (Fabaceae, Asteraceae and Umbelliferae). In the legume Medicago truncatula these signals stimulate root growth and branching by the symbiotic DMI signalling pathway. These findings provide a better understanding of the evolution of signalling mechanisms involved in plant root endosymbioses and will greatly facilitate their molecular dissection. They also open the way to using these natural and very active molecules in agriculture.

Climate change necessitates the development of improved crops capable of withstanding future weather patterns. Carrots ( Daucus carota L.), a crucial vegetable crop of global importance, face unique challenges in seed germination and seedling development due to their complex pollination biology and outcrossing reproduction mode with severe inbreeding depression if selfed. This study investigated the effects of salinity and drought stress on carrot seed germination and seedling development, with focus on the roles of seed priming, cellular processes inhibitors, and biochemical responses. Seed priming agents were hypothesized to enhance stress tolerance by modulating specific cellular and biochemical pathways, such as improving osmotic balance, enhancing antioxidant defense mechanisms, and activating stress-responsive genes. We also hypothesized that specific cellular processes and biochemical pathways influence the germination and early seedling growth of carrot seeds under salinity or drought stress. To test that hypothesis, we evaluated the effects of seed priming with various agents (e.g., water, NaCl, PEG, GA 3 ) on germination rates and seedling vigor. Additionally, we investigated the impact of inhibitors (actinomycin D—inhibitor of transcription, cycloheximide—inhibitor of translation, hydroxyurea—inhibitor of DNA synthesis, cytochalasin—inhibitor of actin polymerization) on seed germination under stress conditions. Biochemical responses, including reactive oxygen species (ROS) levels and antioxidant enzyme activities, were analyzed to identify genotype-specific adaptations indicative of stress tolerance. Our results revealed significant variability in germination rates and seedling growth among the studied carrot experimental lines and commercial cultivars under salinity or drought stress Seed priming enhanced germination and seedling vigor by up to 35% under salinity stress and 28% under drought stress, with notable differences observed across the priming agents. The application of inhibitors highlighted the involvement of specific cellular processes in regulation of seed germination under stress. For instance, actinomycin D reduced germination by 40% under salinity stress. Biochemical analyses indicated genotype-specific responses, with variations in ROS levels and antioxidant enzyme activities such as superoxide dismutase and peroxidase. ROS levels increased by 50% under drought stress, whereas antioxidant enzyme activities varied substantially among genotypes. These findings underscored the importance of genotype-specific adaptations in conferring salinity or drought tolerance in carrot seedlings. Future research integrating omics approaches (e.g., transcriptomics, proteomics, metabolomics) will provide deeper insights into the molecular mechanisms that regulate stress tolerance, to aid in the development of more resilient carrot varieties suitable for cultivation under adverse environmental conditions.

Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing Pseudomonas bacteria (PSB) could potentially interact synergistically because PSB solubilize phosphate into a form that AMF can absorb and transport to the plant. However, very little is known about the interactions between these two groups of microorganisms and how they influence the growth of each other. We tested whether different strains of bacteria, that have the capacity to solubilize phosphate, are able to grow along AMF hyphae and differentially influence the growth of AMF both outside the roots of carrot in in vitro conditions and inside the roots of potato in the presence of a microbial community. We found strong effects of AMF on the growth of the different bacterial strains. Different bacterial strains also had very strong effects on the growth of AMF extraradical hyphae outside the roots of carrot and on colonization of potato roots by AMF. The differential effects on colonization occurred in the presence of a microbial community. Our results show that these two important groups of rhizosphere microorganisms indeed interact with each other. Such interactions could potentially lead to synergistic effects between the two groups but this could depend on whether the bacteria truly solubilize phosphate in the rhizosphere in the presence of microbial communities.

Plants subjected to wounding stress produce secondary metabolites. Several of these metabolites prevent chronic diseases and can be used as colorants, flavors and as antimicrobials. This wound-induced production of plant secondary metabolites is mediated by signaling-molecules such as reactive oxygen species (ROS), ethylene (ET) and jasmonic acid (JA). However, their specific role and interactions that modulate the wound-respond in plants is not fully understood. In the present study, a subtractive cDNA library was generated, to better understand the global response of plants to wounding stress. Carrot ( Daucus carota ) was used as a model system for this study. A total of 335 unique expressed sequence tags (ESTs) sequences were obtained. ESTs sequences with a putative identity showed involvement in stress-signaling pathways as well as on the primary and secondary metabolism. Inhibitors of ROS biosynthesis, ET action and JA biosynthesis alone and in combination were applied to wounded-carrots in order to determine, based on relative gene expression data, the regulatory role of ET, JA and ROS on the wound-response in plants. Our results demonstrate that ROS play a key role as signaling-molecules for the wound-induced activation of the primary and secondary metabolism whereas ET and JA are essential to modulate ROS levels.