Localization of BR-bodies in Sinorhizobium meliloti During Host Colonization
Nima Pendar
Department of Biology
Faculty Supervisor: Joseph C. Chen
Bacterial Ribonucleoprotein (BR)-bodies are novel, membraneless organelles that organize and facilitate RNA degradation. We examined and compared the localization of BR-bodies in wild-type and mutant strains of Sinorhizobium meliloti to investigate their activity during microbe-host interactions. Known for forming symbiosis with compatible legume plants, S. meliloti is a bacterium that colonizes root nodules to fix nitrogen for the host. In S. meliloti, RNase E is essential for viability, and its C-terminal intrinsically disordered region (IDR) is necessary for the assembly of BR-bodies but not required for viability. In free-living, wild-type S. meliloti, BR-bodies assemble to promote RNA degradation, while in IDR deletion mutants, the truncated RNase E fails to organize into BR-bodies, and RNA decay is slowed. Because mutants with truncated RNase E fail to establish effective symbiosis, we hypothesized that BR-bodies must assemble in root nodules for successful interaction with the host plant. To assess the subcellular localization of BR-bodies in symbionts, we infected plants with S. meliloti strains expressing YFP fused to wild-type or mutant RNase E. Three to six weeks after inoculation, BR-body assembly was examined using confocal fluorescence microscopy. Results suggest that wild-type and mutant RNase exhibit different localization patterns in differentiated bacteria inside plant cells.