Casuarinas are actinorhizal tropical trees belonging to the family Casuarinaceae and are capable of forming nitrogen fixing root nodules with an actinomycetal microorganism known as Frankia. In order to identify genes involved in Casuarina-Frankia symbiosis, a Casuarina glauca root nodule cDNAs library was constructed and screened differentially with root and nodule cDNA probes. Here, we present the characterization of several C. glauca transcripts identified by sequence analysis of cDNA clones. In order to study the symbiotic genes in Casuarina glauca root nodules, two genetic transformation systems were developed in Casuarinaceae using Agrobacterium rhizogenes and Agrobacterium tumefaciens. Expression of symbiotic genes was studied in transgenic root nodules.