The invention provides an AtCel5 promoter isolated from Arabidopsis thaliana that is expressed exclusively in root cap cells of both primary and secondary roots. AtCel5 is believed to be a soluble and secreted protein that plays a role in the sloughing of root cap cells from the root tip. The sloughing of root cap cells from the root tip is important because it assists the growing root in penetrating the soil. The AtCel5 gene promotor provides a new molecular marker to further analyze the process of root cap cell separation and also provides a root cap specific promoter for targeting to the environment genes with beneficial properties for plant growth.