CPP1, a DNA-binding protein involved in the expression of a soybean leghemoglobin c3 gene

Nodulin genes are specifically expressed in the nitrogen-fixing root nodule s. We have identified a novel type of DNA-binding protein (CPP1) interactin g with the promoter of the soybean leghemoglobin gene Gmlbc3, The DNA-bindi ng domain of CPP1 contains two similar Cys-rich domains with 9 and 10 Cys, respectively, Genes encoding similar domains have been identified in Arabid opsis thaliana, Caenorhabditis elegans, the mouse, and human. The domains a lso have some homology to a Cys-rich region present in some polycomb protei ns, The cpp1 gene is induced late in nodule development and the expression is confined to the distal part of the central infected tissue of the nodule , A constitutively expressed cpp1 gene reduces the expression of a Gmlbc3 p romoter-gusA reporter construct in Vicia hirsuta roots, These data therefor e suggest that CPP1 might be involved in the regulation of the leghemoglobi n genes in the symbiotic root nodule.