Root heteroblastic development during early sporophyte ontogeny and the developmental anatomy of the fifth root were characterized in previous investigations of the homosporous fern Ceratopteris richardii. Here we report preliminary results of a molecular genetic study of root development in C. richardii. Total mRNA was extracted from gametophytes, sporophylls, and roots of the species. Reverse transcription-polymerase chain reaction (RT-PCR) was employed to copy cDNAs from the original RNA populations. The differential display-polymerase chain reaction (DD-PCR) technique was used to identify putative root specific cDNAs. Six root specific subclones were recovered from a display of 6 primer combinations. Northern analysis of the first subclone (designated as RSG1) has confirmed that it is specifically expressed in roots of C. richardii. Efforts are in progress to characterize the full-length sequence of RSG1 and determine its expression pattern in situ.

Key words: Ceratopteris richardii, root development, root specific gene