Contribution of transgenic Casuarinaceae to our knowledgeof the actinorhizal symbioses

摘要

The Casuarinaceae family is a group of 96species of trees and shrubs that are tolerant to adverse soiland climatic conditions. In the field, Casuarinaceae bearsnitrogen-fixing root nodules (so called actinorhizal nodules)resulting from infection by the soil actinomycete Frankia.The association between Casuarina and Frankia is oftremendous ecological importance in tropical and subtropicalareas where these trees contribute to land stabilization andsoil reclamation. During differentiation of the actinorhizalnodule, a set of genes called actinorhizal nodulins is activated in the developing nodule. Understanding themolecular basis of actinorhizal nodule ontogenesis requiresmolecular tools such as genomics together with gene transfertechnologies for functional analysis of symbiotic genes.Using the biological vectors Agrobacterium rhizogenes andA. tumefaciens, gene transfer into the two species Allocasuarina verticillata and Casuarina glauca has been successful. Transgenic Casuarinaceae plants proved to be valuabletools for exploring the molecular mechanisms resulting fromthe infection process of actinorhizal plants by Frankia.