--P. Suprasanna, K. V. Rao and G. M. Reddy

In maize, the Pr locus controls the hydroxylation pattern of the B-ring of anthocyanin, but the exact position in the known gene action sequence is not clear. Mutants recessive for pr in combination with other anthocyanin genes like a and a2 have been studied in an attempt to understand the hydroxylation pattern of intermediates in anthocyanin biosynthesis in maize. It is not clear whether the 3' hydroxylation occurs at the 9 carbon or 15 carbon level after closure of the ring. In the present report, aleurone extracts from homozygous double recessive mutants c2 pr, bz pr and single recessive mutants c2 Pr and bz Pr were analyzed and the accumulated compounds were isolated and characterized by spectrophotometric and chromatographic methods.

Homozygous double recessive c2 pr accumulated p-coumaric acid, and recessive c2 Pr cinnamic acid, which differ in the hydroxylation groups (Fig. 1). Aleurone extracts of bz Pr contained luteolinidin and double recessive bz pr contained apigenidin, suggesting that hydroxylation occurs prior to Bz in the gene action sequence proposed by Reddy and Coe (1962). The presence of cinnamic acid in c2 Pr and p-coumaric acid in c2 pr suggest that hydroxylation may occur after C2 in the gene action sequence. These observations further offer evidence on the nature of hydroxylation pattern of the B-ring. Enzymatic studies with specific genotypes may provide further insight in the hydroxylation of the anthocyanin molecule in the biosynthetic pathway in maize.

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