Molecular analysis of the maize anthocyanin regulatory locus C1.

Abstract

The Cl gene of maize plays a regulatory role in the production of anthocyanin pigments in the aleurone layer of the endosperm. As an initial step toward understanding the molecular details of how Cl controls pigment biosynthesis, we cloned the Cl gene. This was accomplished by first cloning a mutable allele of Cl, cl-mS, which contains the transposable element Spm. A combination of molecular and genetic analysis was used to identify the Spm at the Cl locus. Individual genomic DNAs from a population in which the cl-mutable phenotype was segregating with the recessive cl phenotype were digested with methyl-sensitive restriction enzymes and probed with a small DNA fragment derived from a defective Spm. One Sal I restriction fragment complementary to the Spm probe was shown to be present in the DNA of individuals with the cl-m5 phenotype but absent from DNA of individuals with a recessive cl phenotype. Subsequent cloning and restriction analysis of this fragment revealed sequences flanking the Spm that proved to be Cl-specific. A DNA fragment derived from the flanking sequences was then used as a probe to clone the wild-type Cl gene and several additional alleles of Cl, including one stable recessive, two mutations caused by Ds insertions, one mutation induced by insertion of a defective Spm, and two dominant mutations, Cl-S and C1-. RNA blot hybridization analysis of three Cl alleles indicates that Cl regulation of the Bzl and Al structural genes in the anthocyanin biosynthetic pathway is at the transcriptional level.

Identification of functional domains in the maize transcriptional activator C1: comparison of wild-type and dominant inhibitor proteins.

“…1) were not observed to trans-activate the Bzl promoter (Table 1). These results clearly demonstrate that the presence of the CI gene product activates the Bzl promoter in cl aleurones and in cl Rscm2 embryos, as expected from previous genetic studies (Dooner and Nelson 1979;Dooner 1983;Cone et al 1986). …”

“…Sequence analysis of the coding regions of the R (Ludwig et al 1989;Perrot and Cone 1989) and Cl (Paz-Ares et al 1987) genes provides molecular evidence in support of the proposed regulatory roles of the encoded proteins (Cone et al 1986;Paz-Ares et al 1986;Ludwig et al 1989). The B gene is homologous to the R gene (Chandler et al 1989), and both B and R encode proteins with homology to the helix-loop-helix subunit dimerization region of the myc family of proteins (Chandler et al 1989;Ludwig et al 1989;Perrot and Cone 1989).…”

A comparative study of Tam3 and Ac transposition in transgenic tobacco and petunia plants

“…The isolation and characterization of maize transposable elements has led to the application of the cloned transposons as probes for the detection of mutated plant genes [6,11,25,26,27]. These transposon tagging experiments indicate that mutated plant genes are preferably isolated from lines which 1) carry mutations that confer a clearly distinguishable phenotype and 2) have a low copy number of the active transposable element in their genome.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…The C1 protein activates transcription of genes encoding enzymes involved in the anthocyanin biosynthesis in the outer layer of cells (aleurone) of the maize seed endosperm (Paz-Ares et al 1987;Cone et al 1986). While C1 is active in aleurone, a very similar MYB protein, P1, is functional in controlling anthocyanin biosynthesis in the maize plant where it interacts with other members of the R-protein family to activate anthocyanin biosynthetic gene expression (Cone et al 1993).…”