Production of ketocarotenoids in transgenic carrot plants with an enhanced level of β-carotene

Biotechnology for Enhanced Nutritional Quality in Plants

“…However, transgenic roots accumulated only 34% of the β-carotene content of wild type carrots due to the hydroxylation of the native β-carotene pool (Jayaraj et al, 2008). Results of recent work to produce ketocarotenoids in carrot roots were inconsistent with the previous work in terms of altered β-carotene accumulation (Ahn et al, 2012). Ahn et al (2012) used the same enzyme, β-carotene ketolase from Haematococcus pluvialis; however; they used the sweet potato ibAGP1 promoter to drive the expression of the CrtW cDNA and the ibAGP1 transit peptide to target the enzyme into plastids.…”

“…Results of recent work to produce ketocarotenoids in carrot roots were inconsistent with the previous work in terms of altered β-carotene accumulation (Ahn et al, 2012). Ahn et al (2012) used the same enzyme, β-carotene ketolase from Haematococcus pluvialis; however; they used the sweet potato ibAGP1 promoter to drive the expression of the CrtW cDNA and the ibAGP1 transit peptide to target the enzyme into plastids. Astaxanthin accumulation was visible to the naked eye as a reddish orange color of the roots with 17.2 μg/g DW of the pigment measured in the highest accumulating line.…”

“…These pigments have high antioxidant activity (Ahn et al, 2012). Among keto-carotenoids, astaxanthin (3,3 -dihydroxy-β, β-carotene-4,4 -dione) was reported to have antioxidant activity several times higher than β-carotene and α-tocopherol .…”

“…Although the same algal enzyme was used to transform the plants in both studies, the β-carotene pool was presumably consumed as substrate in the former study. Ahn et al (2012) suggested that sequence dissimilarity between their algal β-carotene ketolase cDNA and the gene used by Jayaraj et al (2008) may have given rise to differential substrate preference. Another explanation provided by the authors was the differences in the expression systems that were used in the two studies.…”

Enhanced Antioxidant and Protective Activities on Retinal Ganglion Cells of Carotenoids-Overexpressing Transgenic Carrot

“…It has been reported that astaxanthin possesses various biological activities including strong antioxidant, immune-potentiating, hypotensive, neuroprotective, and hepatoprotective activities [6][7][8][9][10]. In a previous study, we reported that HpBkt-transgenic carrot plants had been generated to overproduce carotenoids including astaxanthin, which is a non-natural ketocarotenoid in this plant, using a storage root (ibAGP1) promoter, an amyloplast targeting sequence (TP1) and a single -carotene ketolase (HpBkt) gene [11].…”