Inheritance of Endosperm Color in Maize

White, Orland E.

doi:10.2307/2434971

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“…Although the striking dominant white phenotype of Wc in yellow maize ( Y1 ) was reported a century ago (White 1917), its contribution to selection and breeding of both traditional and modern white-grain maize has been largely unappreciated. Homozygous y1 progeny obtained from crossing white ( y1 ) and yellow ( Y1 ) inbreds often have off-white (“dingy”) phenotypes due to the presence of residual pigment (Poneleit 2001; Stinard 2010).…”

Section: Discussionmentioning

confidence: 99%

“…In addition to the recessive y1 , a white endosperm can result from dominant alleles of White Cap ( Wc ). The dominant nature of Wc , which has been known for at least a century (White 1917; Brink 1930), implies a mechanism for negative regulation of carotenoid accumulation in the developing maize kernel. Wc occurs in commercially important white and sweet corn varieties (Hannah and McCarty 1991).…”

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confidence: 99%

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Structure and Origin of the White Cap Locus and Its Role in Evolution of Grain Color in Maize

et al. 2017

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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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Section: Discussionmentioning

confidence: 99%

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confidence: 99%