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Ethylene independent induction of lycopene biosynthesis …

Lois, L.M., Campos, N., Putra, S.R., Danielsen, K., Rohmer, M. and Boronat, A. 2000. Carotenoid biosynthesis during tomato fruit development: regulatory role of 1-deoxy-D-xylulose 5-phosphatesynthase. Plant J., 22:503–513

Ethylene independent induction of lycopene biosynthesis in ..

In plants, jasmonates regulate the synthesis of various secondary metabolites including anthocyanins (; ; ; ), glucosinolates (; ), caffeoylputrescine () as well as other antioxidants (). Mutants in biosynthesis and signalling pathways contribute most to the understanding of JA functions in plants, especially in Arabidopsis and tomato. In the current study, JA-deficient mutants, spr2 and def1, were used to investigate the role of JA in carotenoid biosynthesis in tomato fruits. Lycopene synthesis was reduced by about 40% in these mutants during fruit ripening (), indicating a positive role of JA in lycopene formation. Several earlier studies suggested that exogenous application of MeJA inhibits lycopene accumulation (). To address this inconsistency, different concentrations of MeJA were applied to wild-type fruits and the result showed that MeJA functions in a dose-dependent fashion. Treatments at lower concentrations (0.05–0.5 µM) promoted lycopene synthesis, while higher concentrations (5 µM and 10 µM) repressed the synthesis of lycopene (). Despite the concentration parameters, the contrary results could also be due to the different application processes. In previous studies, lanolin was used as a MeJA carrier to paste the fruit surface, most likely prolonging the treatment, whereas in the present study, MeJA vapour was used and the treatments lasted for 24h. A similar result was also observed in a previous survey (), in which the lycopene concentration did not change significantly during MeJA exposure, but increased after the treatment. Several exogenous application experiments also observed a stimulation of β-carotene by MeJA, while no remarkable increase was found in this study (data not shown). It seems that the stimulatory effect of JA on carotenoids production is restricted to lycopene in tomato fruit.

Carotenoid biosynthesis during tomato fruit …

A chromoplast-specific carotenoid biosynthesis pathway is revealed by cloning of the tomato white-flower locus.

Bird, C.R., Ray, J.A., Fletcher, J.D., Boniwell, J.M., Bird, A.S., Teulieres, C., Blain, I., Bramley, P.M. and Schuch, W. 1991. Using antisense RNA to study gene function: inhibition of carotenoid biosynthesis in transgenic tomatoes. BioTechnology, 9:635-639

Regulation of carotenoid biosynthesis during tomato fruit development: expression of the gene for lycopene epsilon-cyclase is down-regulated during ripening and is elevated in the mutant Delta.

Potatoes - The World's Healthiest Foods

Identification of the carotenoid isomerase provides insight into carotenoid biosynthesis, prolamellar body formation, and photomorphogenesis.

One of the main characteristics of tomato (Solanum lycopersicum) fruit ripening is a massive accumulation of carotenoids (mainly lycopene), which may contribute to the nutrient quality of tomato fruit and its role in chemoprevention. Previous studies have shown that ethylene (ET) plays a central role in promoting fruit ripening. In this study, the role of jasmonic acid (JA) in controlling lycopene accumulation in tomato fruits was analysed by measuring fruit lycopene content and the expression levels of lycopene biosynthetic genes in JA-deficient mutants (spr2 and def1) and a 35S::prosystemin transgenic line (35S::prosys) with increased JA levels and constitutive JA signalling. The lycopene content was significantly decreased in the fruits of spr2 and def1, but was enhanced in 35S::prosys fruits. Simultaneously, the expression of lycopene biosynthetic genes followed a similar trend. Lycopene synthesis in methyl jasmonate (MeJA) vapour-treated fruits showed an inverted U-shaped dose response, which significantly enhanced the fruit lycopene content and restored lycopene accumulation in spr2 and def1 at a concentration of 0.5 µM. The results indicated that JA plays a positive role in lycopene biosynthesis. In addition, the role of ET in JA-induced lycopene accumulation was also examined. Ethylene production in tomato fruits was depressed in spr2 and def1 while it increased in 35S::prosys. However, the exogenous application of MeJA to Never ripe (Nr), the ET-insensitive mutant, significantly promoted lycopene accumulation, as well as the expression of lycopene biosynthetic genes. Based on these results, it is proposed that JA might function independently of ethylene to promote lycopene biosynthesis in tomato fruits.

Carotenoids are a class of 40-carbon terpenoid molecules that are present in most tissues of higher plants. They are one of the most important plant secondary metabolites that play a variety of roles in plant growth and development. For example, they can serve as attractants to pollinators and animals for seed dispersal by providing fruits and flowers with distinct red, orange, and yellow colours (). They are also important for light harvesting, protecting against excess light energy. In addition, carotenoids are essential components of human diets, providing precursors for vitamin A synthesis and having anti-cancer activities (; ; ). Lycopene, the most abundant carotenoid found in tomatoes, has been regarded as the bioactive component alternative for the remedy of chronic diseases (). The biosynthetic pathway of carotenoids has largely been elucidated. For example, in Arabidopsis and tomato nearly all the key enzymes have been identified (; ; ; ; ). Carotenoids are synthesized in plants through a pathway starting with the formation of phytoene from geranylgeranyl diphosphate (GGPP) in the central isoprenoid pathway and four desaturation steps to produce lycopene.

Fraser, P.D. and Bramley, P.M. 2004. The biosynthesis and nutritional uses of carotenoids. Prog. Lipid Res., 43:228-265
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hydrocarbons: alkanes, alkenes, carotenoids - Lipid

AB - Geranyl diphosphate (GPP), the precursor of most monoterpenes, is synthesized in plastids from dimethylallyl diphosphate and isopentenyl diphosphate by GPP synthases (GPPSs). In heterodimeric GPPSs, a non-catalytic small subunit (GPPS-SSU) interacts with a catalytic large subunit, such as geranylgeranyl diphosphate synthase, and determines its product specificity. Here, snapdragon (Antirrhinum majus) GPPS-SSU was over-expressed in tomato fruits under the control of the fruit ripening-specific polygalacturonase promoter to divert the metabolic flux from carotenoid formation towards GPP and monoterpene biosynthesis. Transgenic tomato fruits produced monoterpenes, including geraniol, geranial, neral, citronellol and citronellal, while exhibiting reduced carotenoid content. Co-expression of the Ocimum basilicum geraniol synthase (GES) gene with snapdragon GPPS-SSU led to a more than threefold increase in monoterpene formation in tomato fruits relative to the parental GES line, indicating that the produced GPP can be used by plastidic monoterpene synthases. Co-expression of snapdragon GPPS-SSU with the O. basilicum α-zingiberene synthase (ZIS) gene encoding a cytosolic terpene synthase that has been shown to possess both sesqui- and monoterpene synthase activities resulted in increased levels of ZIS-derived monoterpene products compared to fruits expressing ZIS alone. These results suggest that re-direction of the metabolic flux towards GPP in plastids also increases the cytosolic pool of GPP available for monoterpene synthesis in this compartment via GPP export from plastids.

Nutrition and Good Health - World Carrot Museum

N2 - Geranyl diphosphate (GPP), the precursor of most monoterpenes, is synthesized in plastids from dimethylallyl diphosphate and isopentenyl diphosphate by GPP synthases (GPPSs). In heterodimeric GPPSs, a non-catalytic small subunit (GPPS-SSU) interacts with a catalytic large subunit, such as geranylgeranyl diphosphate synthase, and determines its product specificity. Here, snapdragon (Antirrhinum majus) GPPS-SSU was over-expressed in tomato fruits under the control of the fruit ripening-specific polygalacturonase promoter to divert the metabolic flux from carotenoid formation towards GPP and monoterpene biosynthesis. Transgenic tomato fruits produced monoterpenes, including geraniol, geranial, neral, citronellol and citronellal, while exhibiting reduced carotenoid content. Co-expression of the Ocimum basilicum geraniol synthase (GES) gene with snapdragon GPPS-SSU led to a more than threefold increase in monoterpene formation in tomato fruits relative to the parental GES line, indicating that the produced GPP can be used by plastidic monoterpene synthases. Co-expression of snapdragon GPPS-SSU with the O. basilicum α-zingiberene synthase (ZIS) gene encoding a cytosolic terpene synthase that has been shown to possess both sesqui- and monoterpene synthase activities resulted in increased levels of ZIS-derived monoterpene products compared to fruits expressing ZIS alone. These results suggest that re-direction of the metabolic flux towards GPP in plastids also increases the cytosolic pool of GPP available for monoterpene synthesis in this compartment via GPP export from plastids.

Managementof orobanche in field crops: A review

Pandurangaiah, S., Ravishankar, K.V., Shivashankar, K.S., Sadashiva, A.T., Pillakenchappa, K. and Narayanan, S.K. 2016. Differential expression of carotenoid biosynthetic pathway genes in two contrasting tomato genotypes for lycopene content. J. Biosci., 41(2):169-324

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