The biosynthesis and nutritional uses of carotenoids.

Carotenoid biosynthesis in flowering plants.

Effects of supplemental light quality on growth and phytochemicals of baby leaf lettuce

The harnessing of solar energy by photosynthesis depends on a safety valve that effectively eliminates hazardous excess energy and prevents oxidative damage to the plant cells. Many of the compounds that protect plant cells also protect human cells. Improving plant resistance to stress may thus have the beneficial side effect of also improving the nutritional quality of plants in the human diet. The pathways that synthesize these compounds are becoming amenable to genetic manipulation, which may yield benefits as widespread as improved plant stress tolerance and improved human physical and mental health.

https://science.sciencemag.org/content/sci/298/5601/2149.full.pdf

Antioxidants in photosynthesis and human nutrition.

Objective: We wanted to determine the total antioxidant capacity (6-hydroxy-2,5,7,8-tetramethyl- chromane-2-carboxylic acid equivalent antioxidant assay; TEAC) of different species and cultivars (strawberry and apple) and to characterize the TEAC among fruits of the same varieties (peach and apricot) but grafted on different rootstocks. Methods: The study was carried out with wild strawberry, six varieties of cultivated strawberry, and five varieties of apple and with apricot and peach grafted on five different rootstocks that are known to induce different plant vigor and fruit qualitative features. The TEAC (considering lipophilic and hydrophilic contributions) was determined for all fruit varieties, and total polyphenol contents were assayed. One-way analysis of variance was used to test differences among fruits and to identify possible correlations of TEAC versus total phenolics. Results: The following hierarchy of antioxidant activities was found: wild strawberries cultivated strawberries kiwifruit apples apricots peaches. Further, differences were found among strawberries with different genotypes and in apricots and peaches grafted from different rootstocks. Conclusions: These observations suggest the importance of genotype for determining antioxidant potential and phenolic contents. Variety manipulation may be a powerful tool for modifying antioxidant fruit patterns and contents. © 2005 Elsevier Inc. All rights reserved.

Basic nutritional investigation Plant genotype affects total antioxidant capacity and phenolic contents in fruit

Cryptochromes are blue light photoreceptors found in plants, bacteria, and animals. In Arabidopsis, cryptochrome 2 (cry2) is involved primarily in the control of flowering time and in photomorphogenesis under low-fluence light. No data on the function of cry2 are available in plants, apart from Arabidopsis (Arabidopsis thaliana). Expression of the tomato (Solanum lycopersicum) CRY2 gene was altered through a combination of transgenic overexpression and virus-induced gene silencing. Tomato CRY2 overexpressors show phenotypes similar to but distinct from their Arabidopsis counterparts (hypocotyl and internode shortening under both low- and high-fluence blue light), but also several novel ones, including a high-pigment phenotype, resulting in overproduction of anthocyanins and chlorophyll in leaves and of flavonoids and lycopene in fruits. The accumulation of lycopene in fruits is accompanied by the decreased expression of lycopene β-cyclase genes. CRY2 overexpression causes an unexpected delay in flowering, observed under both short- and long-day conditions, and an increased outgrowth of axillary branches. Virus-induced gene silencing of CRY2 results in a reversion of leaf anthocyanin accumulation, of internode shortening, and of late flowering in CRY2-overexpressing plants, whereas in wild-type plants it causes a minor internode elongation.

http://www.plantphysiol.org/content/plantphysiol/137/1/199.full.pdf

Manipulation of the Blue Light Photoreceptor Cryptochrome 2 in Tomato Affects Vegetative Development, Flowering Time, and Fruit Antioxidant Content

Ripe tomato fruits accumulate large amounts of the red linear carotene, lycopene (a dietary antioxidant) and small amounts of its orange cyclisation product, beta-carotene (pro-vitamin A). Lycopene is transformed into beta-carotene by the action of lycopene beta-cyclase (beta-Lcy). We introduced, via Agrobacterium-mediated transformation, DNA constructs aimed at up-regulating (OE construct) or down-regulating (AS construct) the expression of the beta-Lcy gene in a fruit-specific fashion. Three transformants containing the OE construct show a significant increase in fruit beta-carotene content. The fruits from these plants display different colour phenotypes, from orange to orange-red, depending on the lycopene/beta-carotene ratio. Fruits from AS transformants show up to 50% inhibition of beta-Lcy expression, accompanied by a slight increase in lycopene content. Leaf carotenoid composition is unaltered in all transformants. In most transformants, an increase in total carotenoid content is observed with respect to the parental line. This increase occurs in the absence of major variations in the expression of endogenous carotenoid genes.

Metabolic engineering of beta-carotene and lycopene content in tomato fruit.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/S0014-5793%2802%2902699-6

Metabolic engineering of xanthophyll content in tomato fruits

Chlamydomonas reinhardtii is an unicellular green alga used for functional genomics studies and heterologous protein expression. A major hindrance in these studies is the low level and instability of expression of nuclear transgenes, due to their rearrangement and/or silencing over time. We constructed dedicated vectors for Agrobacterium-mediated transformation carrying, within the T-DNA borders, the Paromomycin (Paro) selectable marker and an expression cassette containing the Luciferase (Luc) reporter gene. These vectors and newly developed co-cultivation methods were used to compare the efficiency, stability and insertion sites of Agrobacterium- versus electroporation-mediated transformation. The influence of different transformation methods, of the cell wall, of the virulence of different Agrobacterium strains, and of transgene orientation with respect to T-DNA borders were assessed. False positive transformants were more frequent in Agrobacterium-mediated transformation compared to electroporation, compensating for the slightly lower proportion of silenced transformants observed in Agrobacterium-mediated transformation than in electroporation. The proportion of silenced transformants remained stable after 20 cycles of subculture in selective medium. Next generation sequencing confirmed the nuclear insertion points, which occurred in exons or untraslated regions (UTRs) for 10 out of 10 Agrobacterium-mediated and 9 out of 13 of electroporation-mediated insertions. Electroporation also resulted in higher numbers of insertions at multiple loci. Due to its labor-intensive nature, Agrobacterium transformation of Chlamydomonas does not present significant advantages over electroporation, with the possible exception of its use in insertional mutagenesis, due to the higher proportion of within-gene, single-locus insertions. Our data indirectly support the hypothesis that rearrangement of transforming DNA occurs in the Chlamydomonas cell, rather than in the extracellular space as previously proposed.

/pdf/agrobacterium-mediated-and-electroporation-mediated-5agsv3kf4a.pdf

Patrizia Pallara

Papers

Manipulation of the Blue Light Photoreceptor Cryptochrome 2 in Tomato Affects Vegetative Development, Flowering Time, and Fruit Antioxidant Content

Metabolic engineering of beta-carotene and lycopene content in tomato fruit.

Metabolic engineering of xanthophyll content in tomato fruits

Agrobacterium -mediated and electroporation-mediated transformation of Chlamydomonas reinhardtii: a comparative study