The Root Hair: A Single Cell Model for Systems Biology

The root hair cell is the primary site of infection of legumes by rhizobia. Its morphological, physiological, and molecular responses to this symbiotic mutualistic bacterium have been intensively investigated during the past decade especially through the screen of mutants in model legumes such as Medicago truncatula and Lotus japonicus. The identification of mutants defective in nodulation and more specifically in the infection of the root hair cell by rhizobia led to the characterization of genes that belong to the symbiotic pathway. The recent access to isolated soybean (Glycine max) root hair cells inoculated and mock-inoculated with Bradyrhizobium japonicum, the soybean nitrogen-fixing symbiont, opened new avenues to study the response of this single cell type to rhizobia. Taking advantage of the recent improvements in various -omic approaches, researchers are currently using a systems biology approach to better characterize the response of the legume root hair cell to nitrogen-fixing bacteria.