A rice functional transcriptional activator, RISBZ1, responsible for endosperm-specific expression of storage protein genes through GCN4 motif

J Biol Chem. 2001 Apr 27;276(17):14139-52. doi: 10.1074/jbc.M007405200. Epub 2000 Dec 22.


The GCN4 motif, a cis-element that is highly conserved in the promoters of cereal seed storage protein genes, plays a central role in controlling endosperm-specific expression. This motif is the recognition site for a basic leucine zipper transcriptional factor that belongs to the group of maize Opaque-2 (O2)-like proteins. Five different basic leucine zipper cDNA clones, designated RISBZ1-5, have been isolated from a rice seed cDNA library. The predicted gene products can be divided into two groups based on their amino acid sequences. Although all the RISBZ proteins are able to interact with the GCN4 motif, only RISBZ1 is capable of activating (more than 100-fold expression) the expression of a reporter gene under a minimal promoter fused to a pentamer of the GCN4 motif. Loss-of-function and gain-of-function experiments using the yeast GAL4 DNA binding domain revealed that the proline-rich N-terminal domain (27 amino acids in length) is responsible for transactivation. The RISBZ1 protein is capable of forming homodimers as well as heterodimers with other RISBZ subunit proteins. RISBZ1 gene expression is restricted to the seed, where it precedes the expression of storage protein genes. When the RISBZ1 promoter was transcriptionally fused to the beta-glucuronidase reporter gene and the chimeric gene was introduced into rice, the beta-glucuronidase gene is specifically expressed in aleurone and subaleurone layer of the developing endosperm. These findings suggest that the specific expression of transcriptional activator RISBZ1 gene may determine the endosperm specificity of the storage protein genes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Base Sequence
  • Basic-Leucine Zipper Transcription Factors
  • Binding Sites
  • Binding, Competitive
  • Blotting, Northern
  • Cloning, Molecular
  • DNA Methylation
  • DNA, Complementary / metabolism
  • DNA-Binding Proteins*
  • Dimerization
  • Exons
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Gene Library
  • Genes, Reporter
  • Genome, Plant
  • Glucuronidase / genetics
  • Glutathione Transferase / metabolism
  • Leucine Zippers
  • Models, Genetic
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oryza / chemistry
  • Oryza / genetics*
  • Oryza / physiology
  • Phylogeny
  • Plant Physiological Phenomena
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plants, Genetically Modified
  • Plasmids / metabolism
  • Promoter Regions, Genetic
  • Protein Biosynthesis
  • Protein Kinases / metabolism*
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Tissue Distribution
  • Trans-Activators / biosynthesis
  • Trans-Activators / chemistry*
  • Trans-Activators / genetics*
  • Transcription, Genetic
  • Transcriptional Activation*


  • Basic-Leucine Zipper Transcription Factors
  • DNA, Complementary
  • DNA-Binding Proteins
  • Fungal Proteins
  • Plant Proteins
  • RISBZ1 protein, Oryza sativa
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Glutathione Transferase
  • Protein Kinases
  • Glucuronidase