Two cDNA clones (CRH1 and CRH2) homologous to animal calreticulin, a major calcium storage protein in the lumen of the endoplasmic reticulum, were isolated from an ovary cDNA library of barley through differential screening. The two clones differ in the 3 ’ untranslated region and the 5 ‘ region that encodes a putative N-terminal signal sequence. CRHl was mapped to the minus arm of chromosome 1. CRH2 was mapped to the minus arm of chromosome 2. The deduced amino acid sequences share 50 to 55 % identity with animal calreticulins and exhibit the same three-zone characteristic. Recombinant protein stained blue with Stains-all and bound 45Ca*+ when transferred to nitrocellulose membranes. A native protein of ~ 5 kD 5 was identified in ovary extract. Elevated gene expression was observed in ovaries 1 day after pollination and during early embryogenesis. CRHl was expressed at a higher leve1 than CRH2. These studies demonstrate the presence of calreticulin in plant cells and its developmental regulation in fertilization
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