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Abstract Selection for yellow- and white-grain types has been central to postdomestication improvement of maize. While genetic control of carotenoid biosynthesis in endosperm is attributed primarily to the Yellow1 (Y1) phytoene synthase gene, less is known about the role of the dominant white endosperm factor White Cap (Wc). We show that the Wc locus contains multiple, tandem copies of a Carotenoid cleavage dioxygenase 1 (Ccd1) gene that encodes a carotenoid-degrading enzyme. A survey of 111 maize inbreds and landraces, together with 22 teosinte accessions, reveals that Wc is exclusive to maize, where it is prevalent in white-grain (y1) varieties. Moreover, Ccd1 copy number varies extensively among Wc alleles (from 1 to 23 copies), and confers a proportional range of Ccd1 expression in diverse organs. We propose that this dynamic source of quantitative variation in Ccd1 expression was created in maize shortly after domestication by a two-step, Tam3L transposon-mediated process. First, a chromosome segment containing Ccd1 and several nearby genes duplicated at a position 1.9 Mb proximal to the progenitor Ccd1r locus on chromosome 9. Second, a subsequent interaction of Tam3L transposons at the new locus created a 28-kb tandem duplication, setting up expansion of Ccd1 copy number by unequal crossing over. In this way, transposon-mediated variation in copy number at the Wc locus generated phenotypic variation that provided a foundation for breeding and selection of white-grain color in maize.
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The maize PLASTID TERMINAL OXIDASE ( PTOX ) locus controls the carotenoid content of kernels
SUMMARY Carotenoids perform a broad range of important functions in humans; therefore, carotenoid biofortification of maize (Zea maysL.), one of the most highly produced cereal crops worldwide, would have a global impact on human health.PLASTID TERMINAL OXIDASE(PTOX) genes play an important role in carotenoid metabolism; however, the possible function ofPTOXin carotenoid biosynthesis in maize has not yet been explored. In this study, we characterized the maizePTOXlocus by forward‐ and reverse‐genetic analyses. While most higher plant species possess a single copy of thePTOXgene, maize carries two tandemly duplicated copies. Characterization of mutants revealed that disruption of either copy resulted in a carotenoid‐deficient phenotype. We identified mutations in thePTOXgenes as being causal of the classic maize mutant,albescent1. Remarkably, overexpression ofZmPTOX1significantly improved the content of carotenoids, especially β‐carotene (provitamin A), which was increased by ~threefold, in maize kernels. Overall, our study shows that maizePTOXlocus plays an important role in carotenoid biosynthesis in maize kernels and suggests that fine‐tuning the expression of this gene could improve the nutritional value of cereal grains.
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- Award ID(s):
- 2129189
- PAR ID:
- 10530517
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 118
- Issue:
- 2
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- 457 to 468
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/tpj.16618
