Comparative genomics of the nonlegume Parasponia reveals insights into evolution of nitrogen-fixing rhizobium symbioses

Significance Fixed nitrogen is essential for plant growth. Some plants, such as legumes, can host nitrogen-fixing bacteria within cells in root organs called nodules. Nodules are considered to have evolved in parallel in different lineages, but the genetic changes underlying this evolution remain unknown. Based on gene expression in the nitrogen-fixing nonlegume Parasponia andersonii and the legume Medicago truncatula , we find that nodules in...