The Opaque2 b-ZIP transcriptional activator is involved in the transcriptional regulation of genes coding for different types of proteins in the subaleurone layers of the maize endosperm cells. Three wild-type (O2-w1, O2-w2 and O2-w3) and five mutant alleles (o2-T, o2-52, o2-It, o2-R and o2-676) were considered in this study. Western analyses with specific amino terminal and carboxy terminal antisera revealed the presence of differentially shortened o2 polypeptides for some o2 alleles. The nucleotide sequences of the wild-type alleles showed for the deduced polypeptides a highly conserved amino acid sequence having only a short deletion/insertion of a ProlineGlutamic acid motif and glycine residues within the amino terminal part of the protein. The o2-T allele is characterised by a 25 nucleotide deletion that introduces a stop codon 645 bases after the ATG start codon of the longest ORF. This deletion produces a truncated polypeptide (o2-T) missing both the basic and the L- Zipper motifs. Similarly, the o2-52 allele contains an insertion of 4 base pairs 796 bases downstream from the start codon, which causes a frame shift, giving rise to another truncated polypeptide that lacks all the carboxy terminal part downstream the second leucine of the L-Zipper. Conversely, the o2-It allele produces two polypeptides: one of them migrates at a slightly faster rate in SDS-PAGE than do the three wild- types and the second migrates to a position between those of the o2-T and o2-52 proteins. In fact, the o2-It nucleotide sequence shows a deletion of 10 base pairs 711 bases after the start codon, which causes a frame shift that gives rise to a premature stop codon 45 base pairs later. This deletion results a product containing 252 aa residues.
GENE PRODUCTS AND STRUCTURE ANALYSIS OF WILD-TYPE AND MUTANT ALLELES AT THE OPAQUE-2 LOCUS OF Zea mays
2002
Abstract
The Opaque2 b-ZIP transcriptional activator is involved in the transcriptional regulation of genes coding for different types of proteins in the subaleurone layers of the maize endosperm cells. Three wild-type (O2-w1, O2-w2 and O2-w3) and five mutant alleles (o2-T, o2-52, o2-It, o2-R and o2-676) were considered in this study. Western analyses with specific amino terminal and carboxy terminal antisera revealed the presence of differentially shortened o2 polypeptides for some o2 alleles. The nucleotide sequences of the wild-type alleles showed for the deduced polypeptides a highly conserved amino acid sequence having only a short deletion/insertion of a ProlineGlutamic acid motif and glycine residues within the amino terminal part of the protein. The o2-T allele is characterised by a 25 nucleotide deletion that introduces a stop codon 645 bases after the ATG start codon of the longest ORF. This deletion produces a truncated polypeptide (o2-T) missing both the basic and the L- Zipper motifs. Similarly, the o2-52 allele contains an insertion of 4 base pairs 796 bases downstream from the start codon, which causes a frame shift, giving rise to another truncated polypeptide that lacks all the carboxy terminal part downstream the second leucine of the L-Zipper. Conversely, the o2-It allele produces two polypeptides: one of them migrates at a slightly faster rate in SDS-PAGE than do the three wild- types and the second migrates to a position between those of the o2-T and o2-52 proteins. In fact, the o2-It nucleotide sequence shows a deletion of 10 base pairs 711 bases after the start codon, which causes a frame shift that gives rise to a premature stop codon 45 base pairs later. This deletion results a product containing 252 aa residues.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
