The P450‐type carotene hydroxylase PuCHY1 from Porphyra suggests the evolution of carotenoid metabolism in red algae

Abstract

Carotene hydroxylases catalyze the hydroxylation of a-and b-carotene hydrocarbons into xanthophylls. In red algae, b-carotene is a ubiquitously distributed carotenoid, and hydroxylated carotenoids such as zeaxanthin and lutein are also found. However, no enzyme with carotene hydroxylase activity had been previously identified in red algae. Here, we report the isolation of a gene encoding a cytochrome P450-type carotene hydroxylase (PuCHY1) from Porphyra umbilicalis, a red alga with an ancient origin. Sequence comparisons found PuCHY1 belongs to the CYP97B subfamily, which has members from different photosynthetic organisms ranging from red algae to land plants. Functional complementation in Escherichia coli suggested that PuCHY1 catalyzed the conversion from b-carotene to zeaxanthin. When we overexpressed PuCHY1 in the Arabidopsis thaliana chy2 mutant, pigment analysis showed a significant accumulation of hydroxylated carotenoids, including neoxanthin, violaxanthin, and lutein in the leaves of transgenic plants. These results confirmed a b-hydroxylation activity of PuCHY1, and also suggested a possible e-hydroxylation function. The pigment profile and gene expression analyses of the algal thallus under high-light stress suggested that P. umbilicalis is unlikely to operate a partial xanthophyll cycle for photoprotection.Keywords: Bangiales; carotene hydroxylase; carotenoid metabolism; CYP97B; cytochrome P450; Porphyra umbilicalis; red algae Citation: Yang LE, Huang XQ, Hang Y, Deng YY, Lu QQ, Lu S (2014) The P450-type carotene hydroxylase PuCHY1 from Porphyra suggested the evolution of carotenoid metabolism in red algae. J Integr Plant Biol 56: 902-915.

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“…CYP97A appears to be responsible for catalyzing the hydroxylation of the β-ring of α-carotene whereas CYP97C is mainly active against the ε-ring5560. The enzyme PuCHY1, a CYP97B produced by the red alga Porphyra umbilicalis , is also responsible for β-ring hydroxylation61. We found that Zmbch2 mRNA accumulated to levels 100-fold greater than Zmbch1 mRNA and that Zmcyp97a and Zmcyp97b were expressed at levels at least 10-fold higher than Zmcyp97c in the endosperm of both the greenhouse and field plants.…”

Cloning and Functional Characterization of a Lycopene β-Cyclase from Macrophytic Red Alga Bangia fuscopurpurea

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“…The lack of transit peptides and the more distant relationship of the ZEP‐like proteins from P. yezoensis , P. purpurea and P . umbilicalis to ZEP proteins with proven catalytic activity (Figure ), together with the absence of epoxy‐carotenoids in the three algae (Schubert et al ., ; Gantt et al ., ; Yang et al ., ; Takaichi et al ., ) argue against their previous assignment as zeaxanthin epoxidases. Based on the phylogenetic tree in Figure and the absence of epoxy‐carotenoids in Calothrix sp.…”

“…Based on sequence similarity on the protein level, putative ZEP genes have been reported from several red algae of the order Bangiales. ZEP-related sequences were found in two species of Porphyra and in Pyropia yezoensis (Yang et al, 2014;Mikami et al, 2016), but HPLC analyses failed to detect epoxy-carotenoids in any of these species Gantt et al, 2010;Yang et al, 2014;Takaichi et al, 2016). Recently, genomic and transcriptomic sequence data have become available from an increasing number of algae, enabling homology-based searches for candidate genes involved in biochemical pathways with a much broader taxon sampling.…”