Molecular analysis of the c2 locus

The c2 locus is one of the structural genes involved in anthocyanin biosynthesis. This locus was cloned from the Spm (En) induced mutants c2-m1 (unstable) and c2-m2 (stable; McClintock, B., Carnegie Inst. Yearbook 65:568-578) as well as from the wild type allele (C2). The En1 element (Pereira, A., et al., EMBO J. 4:17-23, 1985) was originally used to probe a genomic library constructed from the mutable c2-m1 allele (this mutant contains the autonomous Spm at c2). A clone containing a major part of an En1 element was isolated. Sequences of this clone flanking the element were shown to be c2-specific by using them as probes for cloning of the c2-m2 and C2 allele. From the c2-m2 allele a clone could be isolated containing an Spm deletion derivative (Spm-I2), 3kb in size. The clone isolated from C2 did not contain Spm-element-specific sequences. Northern experiments using part of this clone as probe light up a mRNA of about 1.5kb. A cDNA clone homologous to this mRNA was isolated and partially sequenced. On the amino acid level this sequence showed strong homology to the amino acid sequence of parsley chalcone synthase. These data positively confirm those of Hugo Dooner (Mol. Gen. Genet. 189:136-141, 1983), who suggested on the basis of enzyme activity measurements that C2 encodes chalcone synthase.

Udo Wienand, Ulrike Weydemann, Ursula Niesbach-Klosgen, Peter A. Peterson1 and Heinz Saedler

1Dept. of Agronomy, Iowa State University

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