Carotenoid Isomerase Is Key Determinant of Petal Color of Calendula officinalis

Sanae Kishimoto,Akemi Ohmiya

doi:10.1074/jbc.m111.300301

Sanae Kishimoto, Akemi Ohmiya

Open Access

https://doi.org/10.1074/jbc.m111.300301

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Abstract

Orange petals of calendula (Calendula officinalis) accumulate red carotenoids with the cis-configuration at the C-5 or C-5' position (5-cis-carotenoids). We speculated that the orange-flowered calendula is a carotenoid isomerase (crtiso) loss-of-function mutant that impairs the cis-to-trans conversion of 5-cis-carotenoids. We compared the sequences and enzyme activities of CRTISO from orange- and yellow-flowered calendulas. Four types of CRTISO were expressed in calendula petals. The deduced amino acid sequence of one of these genes (CoCRTISO1) was different between orange- and yellow-flowered calendulas, whereas the sequences of the other three CRTISOs were identical between these plants. Analysis of the enzymatic activities of the CoCRTISO homologs showed that CoCRTISO1-Y, which was expressed in yellow petals, converted carotenoids from the cis-to-trans-configuration, whereas both CoCRTISO1-ORa and 1-ORb, which were expressed in orange petals, showed no activity with any of the cis-carotenoids we tested. Moreover, the CoCRTISO1 genotypes of the F2 progeny obtained by crossing orange and yellow lines linked closely to petal color. These data indicate that CoCRTISO1 is a key regulator of the accumulation of 5-cis-carotenoids in calendula petals. Site-directed mutagenesis showed that the deletion of Cys-His-His at positions 462-464 in CoCRTISO1-ORa and a Gly-to-Glu amino acid substitution at position 450 in CoCRTISO1-ORb abolished enzyme activity completely, indicating that these amino acid residues are important for the enzymatic activity of CRTISO.

Highlights

Reddish 5-cis-carotenoids accumulate in the orange but not yellow petals of calendula
Analysis of the enzymatic activities of the CoCRTISO homologs showed that CoCRTISO1-Y, which was expressed in yellow petals, converted carotenoids from the cis-to-trans-configuration, whereas both CoCRTISO1-ORa and 1-ORb, which were expressed in orange petals, showed no activity with any of the cis-carotenoids we tested
The carotenoids that accumulate in petals are generally in the all-trans form, we previously demonstrated that the petals of some Asteraceae plants contain various types of cis-carotenoids, which are rarely found in plants; for example, the orange petals of calendula (Calendula officinalis), osteospermum (Osteospermum ecklonis), and Gazania spp. accumulate 5-cis-carotenoids2, which have the cis-configuration at the C-5 or C-5Ј position [12, 13]

Summary

Background

Reddish 5-cis-carotenoids accumulate in the orange but not yellow petals of calendula. The CoCRTISO1 genotypes of the F2 progeny obtained by crossing orange and yellow lines linked closely to petal color These data indicate that CoCRTISO1 is a key regulator of the accumulation of 5-cis-carotenoids in calendula petals. The carotenoids that accumulate in petals are generally in the all-trans form, we previously demonstrated that the petals of some Asteraceae plants contain various types of cis-carotenoids, which are rarely found in plants; for example, the orange petals of calendula (Calendula officinalis), osteospermum (Osteospermum ecklonis), and Gazania spp. accumulate 5-cis-carotenoids (mostly 5-cis-lycopenes), which have the cis-configuration at the C-5 or C-5Ј position [12, 13] These carotenoids are reddish and found in negligible quantities in yellow petals. CRTISOs were cloned from crtiso mutant plants such as arabidopsis (Arabidopsis thaliana) ccr

The abbreviations used are

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DISCUSSION