Control of anthocyanin synthesis by the C locus in maize

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Abstract
Alleles at the C locus in maize include C, one of the complementary genes required for anthocyanin pigmentation in the aleuone tissue of the mature kernel; C-I, dominant inhibitor of pigmentation; and c, recessive colorless. The recessive colorless alleles can be differentiated into two distinct forms: c-p (p for positive), conditional colored, develops pigment in the light during germination; c-n (n for negative), colorless, fails to develop pigment at any time. Four-point linkage data support the differentiation of c-p (in the alleles derived from either W22 or K55 inbreds) from c-n. Light and germination conditions are both required for anthocyanin synthesis in c-p tissue, but light “induction” and germination “induction” are two separable events inasmuch as the light stimulus can be stored. The ratio between the two major pigments, cyanidin and pelargonidin, is lowered in c-p tissue relative to that in dominant colored (C) tissue for the W22 allele and background but not for the K55 allele and background. Segregation tests reveal that the difference in the cyanidin-to-pelargonidin ratio in the C and the c-p tissue of W22 background is associated with the C locus. Several properties of the C locus, including anomalous allelic functions, stage- and condition-dependent anthocyanin synthesis controlled by its multiple allelic series, and tissue-specific function, suggest that C may be a regulatory locus in the control of anthocyanin synthesis in aleurone tissue.