Expression of Host Genes During Symbiotic Nitrogen Fixation

Abstract

Rhizobium-legume association which results in the development of root nodule structures is restricted by a narrow host and bacterial range for each species (Pueppke et al. 1978). This suggests a highly specific interaction between the two organisms. Besides infection, the development of the root nodule is also influenced by both bacterial (Maier and Brill 1976) and plant genes (Holl and LaRue 1976). Mutation in any of these organisms may abort the development of the nodule structure and thus affect the process of symbiotic nitrogen fixation. Although it is apparent that the specific expression of both plant and bacterial genes is required during this process, it is not known how many structural genes of the host or bacteria are involved in the development of the symbiosis necessary for nitrogen fixation in legumes. While some progress has been made on Rhizobium genetics, and the control of nitrogenase enzyme in bacteria, our understanding of the genetic contribution of the host to this process is very limited.