Skip to main content
ISMPMI Congress 2025 Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-403 - Developmental fates and N2-fixing efficiency of bacteroids from determinate and indeterminate legume nodules

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Symbiosis and Mutualism (mycorrhiza and N-fixing Rhizobia)

Within legume root nodules, rhizobia differentiate into bacteroids, which reduce atmospheric N2 into NH3 and secrete it to the host plant. Bacteroids may be swollen and terminally differentiated, as in nodules of legumes in the Invert Repeat Lacking Clade (IRLC), or non-swollen and able to regenerate outside nodules, such as those within the Phaseolid clade. It is unclear why these different modes of endosymbiotic lifestyles exist and whether they differ in symbiotic efficiency. In this work, we compared N2-fixing bacteroids of the near isogenic strains Rhizobium leguminosarum bv. phaseoli 4292 (Rlp4292) and R. leguminosarum bv. viceae A34 (RlvA34) when nodulating Phaseolus vulgaris (common bean) and Pisum sativum (pea). They only differ on the symbiosis (Sym) plasmid, with pRP2 (in strain Rlp4292) being replaced by pRL1 in strain RlvA34, but otherwise share a core genome. In this work, we mapped the genetic, proteomic and developmental changes from the whole plant to nodule and cellular levels to understanding how these different developmental fates alter the symbiotic interaction between legumes and rhizobia. Pea bacteroids fix N2 fixation at higher rates per unit bacteroid protein because expression is skewed towards N2 fixation and central metabolism. Overall, pea bacteroids fix more N2 relative to bean on an individual basis, being also pea bacteroids more densely packed within infected plant cells than bean bacteroids.