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Distinct expression and function of carotenoid metabolic genes and homoeologs in developing wheat grains.

ABSTRACT: ?-carotene, the most active provitamin A molecule produced by plants, plays important roles in human nutrition and health. ?-carotene does not usually accumulate in the endosperm (i.e. flour) of mature wheat grains, which is a major food source of calories for humans. Therefore, enriching ?-carotene accumulation in wheat grain endosperm will enable a sustainable dietary supplementation of provitamin A. Several metabolic genes affecting ?-carotene accumulation have already been isolated from wheat, including phytoene synthase 1 (PSY1), lycopene ?-cyclase (LCYe) and carotenoid ?-ring hydroxylase1/2 (HYD1/2).In this work, we cloned and biochemically characterized two carotenoid cleavage dioxygenases (CCDs), CCD1 and CCD4, from wheat. While CCD1 homoeologs cleaved ?-apo-8'-carotenal, ?-carotene, lutein and zeaxanthin into apocarotenoid products, CCD4 homoeologs were inactive towards these substrates in in vitro assays. When analyzed by real-time qPCR, PSY1, LCYe, HYD1/2 and CCD1/4 homoeologs showed distinct expression patterns in vegetative tissues and sections of developing tetraploid and hexaploid wheat grains, suggesting that carotenoid metabolic genes and homoeologs are differentially regulated at the transcriptional level in wheat.The CCD1/4 enzyme activity and the spatial-temporal gene expression data provide critical insights into the specific carotenoid metabolic gene homoeologs that control ?-carotene accumulation in wheat grain endosperm, thus establishing the knowledge base for generation of wheat varieties with enhanced ?-carotene in the endosperm through breeding and genome editing approaches.

SUBMITTER: Qin X

PROVIDER: S-EPMC4943016 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Distinct expression and function of carotenoid metabolic genes and homoeologs in developing wheat grains.

Qin Xiaoqiong X Fischer Kathryn K Yu Shu S Dubcovsky Jorge J Tian Li L

BMC plant biology 20160712 1

<h4>Background</h4>β-carotene, the most active provitamin A molecule produced by plants, plays important roles in human nutrition and health. β-carotene does not usually accumulate in the endosperm (i.e. flour) of mature wheat grains, which is a major food source of calories for humans. Therefore, enriching β-carotene accumulation in wheat grain endosperm will enable a sustainable dietary supplementation of provitamin A. Several metabolic genes affecting β-carotene accumulation have already been ...[more]

PMID: 27405473

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Project description:The dietary needs of humans for provitamin A carotenoids arise from their inability to synthesize vitamin A de novo. To improve the status of this essential micronutrient, special attention has been given to biofortification of staple foods, such as wheat grains, which are consumed in large quantities but contain low levels of provitamin A carotenoids. However, there remains an unclear contribution of metabolic genes and homoeologs to the turnover of carotenoids in wheat grains. To better understand carotenoid catabolism in tetraploid wheat, Targeting Induced Local Lesions in Genomes (TILLING) mutants of CCD4, encoding a Carotenoid Cleavage Dioxygenase (CCD) that cleaves carotenoids into smaller apocarotenoid molecules, were isolated and characterized. Our analysis showed that ccd4 mutations co-segregated with Poltergeist-like (pll) mutations in the TILLING mutants of A and B subgenomes, hence the ccd-A4 pll-A, ccd-B4 pll-B, and ccd-A4 ccd-B4 pll-A pll-B mutants were analyzed in this study. Carotenoid profiles are comparable in mature grains of the mutant and control plants, indicating that CCD4 homoeologs do not have a major impact on carotenoid accumulation in grains. However, the neoxanthin content was increased in leaves of ccd-A4 ccd-B4 pll-A pll-B relative to the control. In addition, four unidentified carotenoids showed a unique presence in leaves of ccd-A4 ccd-B4 pll-A pll-B plants. These results suggested that CCD4 homoeologs may contribute to the turnover of neoxanthin and the unidentified carotenoids in leaves. Interestingly, abnormal spike, grain, and seminal root phenotypes were also observed for ccd-A4 pll-A, ccd-B4 pll-B, and ccd-A4 ccd-B4 pll-A pll-B plants, suggesting that CCD4 and/or PLL homoeologs could function toward these traits. Overall, this study not only reveals the role of CCD4 in cleavage of carotenoids in leaves and grains, but also uncovers several critical growth traits that are controlled by CCD4, PLL, or the CCD4-PLL interaction.

Dataset Information

Distinct expression and function of carotenoid metabolic genes and homoeologs in developing wheat grains.

Publications

Distinct expression and function of carotenoid metabolic genes and homoeologs in developing wheat grains.

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