Carotenoids in plant foods provide health benefits by functioning as provitamin A.One ofthe vital provitamin A carotenoids,β-cryptoxanthin,is typically plentiful in citrus fruit.However,little is known about the gene...Carotenoids in plant foods provide health benefits by functioning as provitamin A.One ofthe vital provitamin A carotenoids,β-cryptoxanthin,is typically plentiful in citrus fruit.However,little is known about the genetic basis of β-cryptoxanthin accumulation in citrus.Here,we performed a widely targeted metabolomic analysis of 65 major carotenoids and carotenoid derivatives to characterize carotenoid accumulation in Citrus and determine the taxonomic profile of b-cryptoxanthin.We used data from 81 newly sequenced representative accessions and 69 previously sequenced Citrus cultivars to reveal the genetic basis of β-cryptoxanthin accumulation through a genome-wide association study.We identified a causal gene,CitCYP97B,which encodes a cytochrome P450 protein whose substrate and metabolic pathways in land plants were undetermined.We subsequently demonstrated that CitCYP97B functions as a novel monooxygenase that specifically hydroxylates the β-ring of β-cryptoxanthin in a heterologous expression system.In planta experiments provided further evidence that CitCYP97B negatively regulates b-cryptoxanthin content.Using the sequenced Citrus accessions,we found that two critical structural cis-element variations contribute to increased expression of CitCYP97B,thereby altering β-cryptoxanthin accumulation in fruit.Hybridization/introgression appear to have contributed to the prevalence of two cis-element variations in different Citrus types during citrus evolution.Overall,these findings extend our understanding of the regulation and diversity of carotenoid metabolism in fruit crops and provide a genetic target for production of β-cryptoxanthin-biofortified products.展开更多
Carotene hydroxylases catalyze the hydroxylation of a- and β-carotene hydrocarbons into xanthophylls.In red algae,β-carotene is a ubiquitously distributed carotenoid,and hydroxylated carotenoids such as zeaxanthin a...Carotene hydroxylases catalyze the hydroxylation of a- and β-carotene hydrocarbons into xanthophylls.In red algae,β-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 CYP97 B 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 β-carotene to zeaxanthin.When we overexpressed PuCHYi 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 β-hydroxylation activity of PuCHY1,and also suggested a possible ε-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.展开更多
基金supported by the National Key Research and Develop-ment Program of China(2022YFF1003100)the National Natural Science Foundation of China(31930095)Modern Agro-industry Technology Research System(CARS-26).
文摘Carotenoids in plant foods provide health benefits by functioning as provitamin A.One ofthe vital provitamin A carotenoids,β-cryptoxanthin,is typically plentiful in citrus fruit.However,little is known about the genetic basis of β-cryptoxanthin accumulation in citrus.Here,we performed a widely targeted metabolomic analysis of 65 major carotenoids and carotenoid derivatives to characterize carotenoid accumulation in Citrus and determine the taxonomic profile of b-cryptoxanthin.We used data from 81 newly sequenced representative accessions and 69 previously sequenced Citrus cultivars to reveal the genetic basis of β-cryptoxanthin accumulation through a genome-wide association study.We identified a causal gene,CitCYP97B,which encodes a cytochrome P450 protein whose substrate and metabolic pathways in land plants were undetermined.We subsequently demonstrated that CitCYP97B functions as a novel monooxygenase that specifically hydroxylates the β-ring of β-cryptoxanthin in a heterologous expression system.In planta experiments provided further evidence that CitCYP97B negatively regulates b-cryptoxanthin content.Using the sequenced Citrus accessions,we found that two critical structural cis-element variations contribute to increased expression of CitCYP97B,thereby altering β-cryptoxanthin accumulation in fruit.Hybridization/introgression appear to have contributed to the prevalence of two cis-element variations in different Citrus types during citrus evolution.Overall,these findings extend our understanding of the regulation and diversity of carotenoid metabolism in fruit crops and provide a genetic target for production of β-cryptoxanthin-biofortified products.
基金supported by the State Key Basic Research Project of China(2013CB127004)the National Natural Science Foundation of China(90817002)+2 种基金the Public Science and Technology Research Funds Projects of Ocean(201105023)to S.L.supported by the National Science Foundation of China(J1103512)supported by the National Science Foundation Research Coordination Networks(NSF 0741907,Pls:S.Brawley,E.Gantt,A.Grossman,J.Stiller)
文摘Carotene hydroxylases catalyze the hydroxylation of a- and β-carotene hydrocarbons into xanthophylls.In red algae,β-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 CYP97 B 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 β-carotene to zeaxanthin.When we overexpressed PuCHYi 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 β-hydroxylation activity of PuCHY1,and also suggested a possible ε-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.
