Endosperm Box Binding Proteins: cDNA Cloning of a Wheat HMG Protein

ABSTRACT

Prolamins are the main storage proteins of the Triticeae and their genes are transcriptionally regulated. A sequence, called the endosperm box, is a putative cis-acting element present in several prolamin genes. The 3′ part of this consensus contain a palindromic sequence typically bounded by bZIP transcription factors. The 5′ part is also present in zein gene promoters. We have shown by mobility shift assays showed that different endosperm nuclear proteins can interact with both parts of the endosperm box sequence and with a related sequence present in the high molecular weight (HMW) glutenin gene promoters. By screening an expression library with an oligonucleotide containing the endosperm box, we have cloned a cDNA coding for a wheat HMG1-like protein. The conserved amino acids sequence of the plant HMG1-like proteins and their features support the putative function of the wheat HMG1-like protein in prolamin gene transcriptional regulation.