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OHP1: a maize basic domain/leucine zipper protein that interacts with opaque2
L D Pysh1, M J Aukerman, R J Schmidt
1Department of Biology, University of California, San Diego, La Jolla 92093-0116.
The Plant Cell
|February 1, 1993
Summary
Researchers identified Opaque Hydrogen Peroxide 1 (OHP1), a novel bZIP protein that interacts with Opaque2 (O2) to regulate zein gene expression in maize. OHP1 forms complexes with O2, influencing transcription of storage proteins.
Area of Science:
- Plant Molecular Biology
- Transcriptional Regulation
- Maize Genetics
Background:
- OPAQUE2 (O2) is a key regulatory gene controlling the transcription of 22-kD zein storage protein genes in maize.
- The O2 protein, a bZIP transcription factor, binds zein gene promoters as a homodimer in vitro and potentially as a heterodimer in vivo.
Purpose of the Study:
- To identify novel bZIP proteins interacting with O2.
- To characterize the function and interaction of a newly identified bZIP protein, OHP1, in zein gene regulation.
Main Methods:
- Screening of a maize endosperm cDNA library using a bZIP motif from O2.
- Sequence analysis of isolated cDNAs.
- In vitro binding assays for OHP1 homodimer and O2-OHP1 heterodimer formation.
- Whole genome DNA gel blot and RNA gel blot analyses.
Main Results:
- A partial cDNA encoding OHP1, a bZIP protein similar to O2, was isolated.
- OHP1 binds O2 target sites as both a homodimer and a heterodimer with O2.
- OHP1 is transcribed as a 1.7-kb mRNA expressed in most maize organs and in various zein-mutant endosperms.
- OHP1 gene loci do not map near known zein regulatory loci.
Conclusions:
- OHP1 is a novel bZIP protein that heterodimerizes with O2, suggesting a role in a complex regulatory network for zein gene expression.
- OHP1's expression pattern and binding capabilities support its involvement in transcriptional regulation of maize seed storage proteins.