Abstract
Summary: We isolated the genes that are specifically or predominantly expressed in the cap of maize primary root by cDNA subtraction and differential screening, and characterized them in detail. One of such genes is a novel glycine-rich protein, zmGRP4(Zea mays glycine-rich protein4).In situ hybridization analysis has shown zmGRP4to be strongly expressed in the lateral root cap and weakly in the root epidermis. Immunoblot and immunohistochemical analysis using a polyclonal antibody raised against zmGRP4 protein revealed that the protein, which is posttranslationally modified, is secreted into and accumulated in the mucilage that covers the root apex. Two novel homologous genes, zmRCP1 a nd zmRCP2(Zea mays root cap-periphery gene), are specifically expressed in a few cell layers of the peripheral root cap. The peripheral root cap cells are namely the sloughing-off cap cells, which may undergo programmed cell death.
