biostudies-literatureUnknown103(13)Mergaert PSymbiosis between legumes and Rhizobium bacteria leads to the formation of root nodules where bacteria in the infected plant cells are converted into nitrogen-fixing bacteroids. Nodules with a persistent meristem are indeterminate, whereas nodules without meristem are determinate. The symbiotic plant cells in both nodule types are polyploid because of several cycles of endoreduplication (genome replication without mitosis and cytokinesis) and grow consequently to extreme sizes. Here we demonstrate that differentiation of bacteroids in indeterminate nodules of Medicago and related legumes from the galegoid clade shows remarkable similarity to host cell differentiation. During bacteroid maturation, repeated DNA replication without cytokinesis results in extensive amplification of the entire Proceedings of the National Academy of Sciences of the United States of America5230-5https://www.ebi.ac.uk/biostudies/studies/S-EPMC1458823biostudies-literatureEukaryotic control on bacterial cell cycle and differentiation in the Rhizobium-legume symbiosis.PMC1458823Catrice OUchiumi TBarloy-Hubler FAlunni BCheron AMausset AEMergaert PKondorosi AGalibert FEvanno GKondorosi EfalseEukaryotic control on bacterial cell cycle and differentiation in the Rhizobium-legume symbiosis.Symbiosis between legumes and Rhizobium bacteria leads to the formation of root nodules where bacteria in the infected plant cells are converted into nitrogen-fixing bacteroids. Nodules with a persistent meristem are indeterminate, whereas nodules without meristem are determinate. The symbiotic plant cells in both nodule types are polyploid because of several cycles of endoreduplication (genome replication without mitosis and cytokinesis) and grow consequently to extreme sizes. Here we demonstrate that differentiation of bacteroids in indeterminate nodules of Medicago and related legumes from the galegoid clade shows remarkable similarity to host cell differentiation. During bacteroid maturation, repeated DNA replication without cytokinesis results in extensive amplification of the entire 2006-01-01T00:00:00Z2006 Mar2026-03-16T16:10:58.417Z2019-03-27T01:26:24ZS-EPMC14588231654712910.1073/pnas.0600912103