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The kiwifruit lycopene beta-cyclase plays a significant role in carotenoid accumulation in fruit.

Ampomah-Dwamena C, McGhie T, Wibisono R, Montefiori M, Hellens RP, Allan AC - J. Exp. Bot. (2009)

Bottom Line: The composition of carotenoids, along with anthocyanins and chlorophyll, accounts for the distinctive range of colour found in the Actinidia (kiwifruit) species.Lutein and beta-carotene are the most abundant carotenoids found during fruit development, with beta-carotene concentration increasing rapidly during fruit maturation and ripening.This indicates that the accumulation of beta-carotene, the major carotenoid in these kiwifruit species, appears to be controlled by the level of expression of LCY-beta gene.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand. cdwamena@hortresearch.co.nz

ABSTRACT
The composition of carotenoids, along with anthocyanins and chlorophyll, accounts for the distinctive range of colour found in the Actinidia (kiwifruit) species. Lutein and beta-carotene are the most abundant carotenoids found during fruit development, with beta-carotene concentration increasing rapidly during fruit maturation and ripening. In addition, the accumulation of beta-carotene and lutein is influenced by the temperature at which harvested fruit are stored. Expression analysis of carotenoid biosynthetic genes among different genotypes and fruit developmental stages identified Actinidia lycopene beta-cyclase (LCY-beta) as the gene whose expression pattern appeared to be associated with both total carotenoid and beta-carotene accumulation. Phytoene desaturase (PDS) expression was the least variable among the different genotypes, while zeta carotene desaturase (ZDS), beta-carotene hydroxylase (CRH-beta), and epsilon carotene hydroxylase (CRH-epsilon) showed some variation in gene expression. The LCY-beta gene was functionally tested in bacteria and shown to convert lycopene and delta-carotene to beta-carotene and alpha-carotene respectively. This indicates that the accumulation of beta-carotene, the major carotenoid in these kiwifruit species, appears to be controlled by the level of expression of LCY-beta gene.

Show MeSH
Carotenoid biosynthetic pathway in plants. Enzymatic conversions are shown by arrows with the enzymes responsible in bold. PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, zeta-carotene desaturase; CRTISO, carotene isomerase; LCY-β, lycopene beta-cyclase; LCY-ε, lycopene epsilon-cyclase; CRH-β, beta-carotene hydroxylase; CRH-ε, epsilon-carotene hydroxylase.
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fig1: Carotenoid biosynthetic pathway in plants. Enzymatic conversions are shown by arrows with the enzymes responsible in bold. PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, zeta-carotene desaturase; CRTISO, carotene isomerase; LCY-β, lycopene beta-cyclase; LCY-ε, lycopene epsilon-cyclase; CRH-β, beta-carotene hydroxylase; CRH-ε, epsilon-carotene hydroxylase.

Mentions: The carotenoid biosynthetic pathway in plants is shown in Fig. 1 (Cunningham et al., 1994; Hirschberg, 2001). The first committed step is the condensation of two molecules of geranyl geranyl pyrophosphate (GGPP) to form phytoene, catalysed by the enzyme phytoene synthase (PSY). The colourless phytoene is subsequently desaturated to give zeta-carotene and lycopene (Norris et al., 1995). In bacteria, the desaturation of phytoene is by one enzyme, carotene desaturase (CrtI) but in plants, two enzymes, phytoene desaturase (PDS) and zeta-carotene desaturase (ZDS) are required (Bartley et al., 1999). The carotenoid pathway branches at the cyclization of lycopene, which is acted upon by lycopene cyclases to produce alpha-carotene and beta-carotene. The formation of alpha-carotene requires the addition of an epsilon ring to one end of the linear lycopene molecule (yielding delta-carotene) by the enzyme lycopene epsilon cyclase (LCY-ε), followed by the activity of lycopene beta-cyclase (LCY-β), which adds a beta ring to the other end of the chain. In contrast, beta -carotene results from the addition of two beta rings to both ends of the linear lycopene molecule by the lycopene beta-cyclase enzyme (LCY-β). The flux through the branches is thus dependent on the relative activities of the cyclases involved. In maize, polymorphisms in LCY-ϵ were found to account for the accumulation of beta-carotene and xanthophylls derived from this carotene (Harjes et al., 2008). Similarly, in the Arabidopsis lut1 and lut2 mutants, in which lutein accumulation is reduced or completely absent, there is an increased accumulation of beta-ring-containing carotenoid compounds (Pogson et al., 1996; Tian et al., 2003). Overexpression of beta-carotene hydroxylase in transgenic Arabidopsis increased the concentrations of xanthophylls without any significant reduction in the amount of other carotenoids, suggesting genetic manipulation of a single step can increase flux through the pathway (Davison et al., 2002).


The kiwifruit lycopene beta-cyclase plays a significant role in carotenoid accumulation in fruit.

Ampomah-Dwamena C, McGhie T, Wibisono R, Montefiori M, Hellens RP, Allan AC - J. Exp. Bot. (2009)

Carotenoid biosynthetic pathway in plants. Enzymatic conversions are shown by arrows with the enzymes responsible in bold. PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, zeta-carotene desaturase; CRTISO, carotene isomerase; LCY-β, lycopene beta-cyclase; LCY-ε, lycopene epsilon-cyclase; CRH-β, beta-carotene hydroxylase; CRH-ε, epsilon-carotene hydroxylase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2736891&req=5

fig1: Carotenoid biosynthetic pathway in plants. Enzymatic conversions are shown by arrows with the enzymes responsible in bold. PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, zeta-carotene desaturase; CRTISO, carotene isomerase; LCY-β, lycopene beta-cyclase; LCY-ε, lycopene epsilon-cyclase; CRH-β, beta-carotene hydroxylase; CRH-ε, epsilon-carotene hydroxylase.
Mentions: The carotenoid biosynthetic pathway in plants is shown in Fig. 1 (Cunningham et al., 1994; Hirschberg, 2001). The first committed step is the condensation of two molecules of geranyl geranyl pyrophosphate (GGPP) to form phytoene, catalysed by the enzyme phytoene synthase (PSY). The colourless phytoene is subsequently desaturated to give zeta-carotene and lycopene (Norris et al., 1995). In bacteria, the desaturation of phytoene is by one enzyme, carotene desaturase (CrtI) but in plants, two enzymes, phytoene desaturase (PDS) and zeta-carotene desaturase (ZDS) are required (Bartley et al., 1999). The carotenoid pathway branches at the cyclization of lycopene, which is acted upon by lycopene cyclases to produce alpha-carotene and beta-carotene. The formation of alpha-carotene requires the addition of an epsilon ring to one end of the linear lycopene molecule (yielding delta-carotene) by the enzyme lycopene epsilon cyclase (LCY-ε), followed by the activity of lycopene beta-cyclase (LCY-β), which adds a beta ring to the other end of the chain. In contrast, beta -carotene results from the addition of two beta rings to both ends of the linear lycopene molecule by the lycopene beta-cyclase enzyme (LCY-β). The flux through the branches is thus dependent on the relative activities of the cyclases involved. In maize, polymorphisms in LCY-ϵ were found to account for the accumulation of beta-carotene and xanthophylls derived from this carotene (Harjes et al., 2008). Similarly, in the Arabidopsis lut1 and lut2 mutants, in which lutein accumulation is reduced or completely absent, there is an increased accumulation of beta-ring-containing carotenoid compounds (Pogson et al., 1996; Tian et al., 2003). Overexpression of beta-carotene hydroxylase in transgenic Arabidopsis increased the concentrations of xanthophylls without any significant reduction in the amount of other carotenoids, suggesting genetic manipulation of a single step can increase flux through the pathway (Davison et al., 2002).

Bottom Line: The composition of carotenoids, along with anthocyanins and chlorophyll, accounts for the distinctive range of colour found in the Actinidia (kiwifruit) species.Lutein and beta-carotene are the most abundant carotenoids found during fruit development, with beta-carotene concentration increasing rapidly during fruit maturation and ripening.This indicates that the accumulation of beta-carotene, the major carotenoid in these kiwifruit species, appears to be controlled by the level of expression of LCY-beta gene.

View Article: PubMed Central - PubMed

Affiliation: The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand. cdwamena@hortresearch.co.nz

ABSTRACT
The composition of carotenoids, along with anthocyanins and chlorophyll, accounts for the distinctive range of colour found in the Actinidia (kiwifruit) species. Lutein and beta-carotene are the most abundant carotenoids found during fruit development, with beta-carotene concentration increasing rapidly during fruit maturation and ripening. In addition, the accumulation of beta-carotene and lutein is influenced by the temperature at which harvested fruit are stored. Expression analysis of carotenoid biosynthetic genes among different genotypes and fruit developmental stages identified Actinidia lycopene beta-cyclase (LCY-beta) as the gene whose expression pattern appeared to be associated with both total carotenoid and beta-carotene accumulation. Phytoene desaturase (PDS) expression was the least variable among the different genotypes, while zeta carotene desaturase (ZDS), beta-carotene hydroxylase (CRH-beta), and epsilon carotene hydroxylase (CRH-epsilon) showed some variation in gene expression. The LCY-beta gene was functionally tested in bacteria and shown to convert lycopene and delta-carotene to beta-carotene and alpha-carotene respectively. This indicates that the accumulation of beta-carotene, the major carotenoid in these kiwifruit species, appears to be controlled by the level of expression of LCY-beta gene.

Show MeSH