Data from: Autopolyploidy alters nodule-level interactions in the legume-rhizobium mutualism

Premise of the study: Polyploidy is a major genetic driver of ecological
and evolutionary processes in plants, yet its effects on plant
interactions with mutualistic microbes remain unresolved. The
legume-rhizobium symbiosis regulates global nutrient cycles and plays a
role in the diversification of legume taxa. In this mutualism, rhizobia
bacteria fix nitrogen in exchange for carbon provided by legume hosts.
This exchange occurs inside root nodules, which house bacterial cells and
represent the interface of legume-rhizobial interactions. Although
polyploidy may directly impact the legume-rhizobium mutualism, no studies
have explored how it alters the internal structure of nodules. Methods: We
created synthetic autotetraploids using Medicago sativa subsp. caerulea.
Neotetraploid plants and their diploid progenitors were singly inoculated
with two strains of rhizobia, Sinorhizobium meliloti and S. medicae.
Confocal microscopy was used to quantify internal traits of nodules
produced by diploid and neotetraploid plants. Key Results: Autotetraploid
plants produced larger nodules with larger nitrogen fixation zones than
diploids across both strains of rhizobia, although significance of this
difference was limited by power. Neotetraploid M. sativa subsp. caerulea
plants also produced symbiosomes that were significantly larger, nearly
twice the size, than those present in diploids. Conclusions: This study
sheds light on how polyploidy directly affects a plant-bacterial mutualism
and uncovers novel mechanisms. Changes in plant-microbe interactions that
directly result from polyploidy likely contribute to the increased ability
of polyploid legumes to establish in diverse environments.