Allele Specific Gene Regulation in Maize Floral Organs

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9601285 Peterson The maize P gene encodes a Myb-homologous transcriptional regulator of three genes for flavonoid pigment biosynthesis in certain maize floral organs. The P-rr allele specifies pigmentation of both the kernel pericarp and cob glumes, while the P-wr allele pigments the cob glumes but not the kernel pericarps. The mechanism(s) leading to organ-specific expression of the P-wr allele will be investigated. It has been found that both tissues contain P-wr transcripts although the pericarps are colorless and the cob glumes are red. It has also been determined that the proteins encoded by these two alleles differ at two positions outside the Myb DNA binding domain and by a truncation and replacement at the C-terminus. A particle-gun based transient assay system will be used to determine which changes in the P-wr protein are responsible for organ-specific expression. In addition to transient assays the in vivo expression pattern of the P-wr allele will be studied by expressing the P-wr cDNA in transgenic plants. It has been found that the P-wr locus contains a repetitive DNA consisting of approximately 5 copies of a 12.6 kb DNA sequence and the genomic organization of the locus will be further investigated. The functional P-wr gene will be identified by the use of a Ds insertion. cDNA clones from two additional P gene alleles will be sequenced and their responsiveness to UFO, a trans-modifier of P-wr expression, will be studied. %%% The results of this study will help to elucidate fundamental regulatory mechanisms which produce specific patterns of gene expression during plant development. ***