Regulation of gamma-zein gene expression in quality protein maize
Abstract
The opaque-2 (o2) mutation in maize confers a soft chalky endosperm due to reduction in prolamine content. Quality Protein Maize genotypes (QPM) were developed in an o2 background using "modifier" genes to overcome these phenotypic defects. These materials were found to contain twice as much 27 kD gamma-zein compared to standard opaque-2 mutants. We have studied the regulation of expression of the gamma-zein gene through analysis of gene copy number, amount of RNA, DNA sequences and specific protein-DNA interactions. The QPM genotypes were found to have gamma-zein gene copy numbers similar to the normal and non-modified opaque-2 inbred lines. RNA analysis revealed that the QPM materials contain approximately two times more gamma-zein mRNA than non-modified genotypes. The coding region and the 5$\sp\prime$ flanking regions of genomic clones of normal and QPM materials were highly homologous except for a 13 bp long "AT" insertion in the QPM gamma-zein gene. The gamma-zein gene 5$\sp\prime$ flanking region was found to bind nuclear proteins from both maize endosperm and seedling nuclei. The proteins associated with the gamma-zein gene were similar to those binding to 19 kD alpha-zein gene promoter sequences. We identified the protein binding regions in the gamma-zein 5$\sp\prime$ flanking region through chemical and DNAse I footprinting. The protein binding regions contained a common motif ATAAAATA, which was similar to the binding region of a transcriptional regulatory protein AT-1 identified in soybean root nodules.
Degree
Ph.D.
Advisors
Larkins, Purdue University.
Subject Area
Biochemistry|Agricultural chemicals|Genetics
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