University of Pittsburgh Department of Biological Sciences Presents
E&E Wednesday Noon Seminars 2017-2018
Graduate student Nicole Forrester - University of Pittsburgh
Plant polyploidy enhances nodule traits and host benefit from the legume-rhizobia mutualism
Polyploidy is a major driver of evolutionary novelty and speciation in plants. Recent work has illuminated how polyploidy affects genotypes, phenotypes, and abiotic interactions, yet little is known about how polyploidy alters plant-biotic interactions. The legume-rhizobia mutualism is an important biotic interaction in which rhizobia bacteria fix nitrogen in exchange for carbon provided by legume hosts. This mutualism regulates global nutrient cycles and plays a prominent role in the distribution and diversification of legumes. Despite the importance of this mutualism, it remains unclear how polyploidy alters mutualism traits and host benefit from it. To address this, I developed a framework of mechanistic hypotheses for how plant polyploidy directly alters the quantity and quality of rhizobial symbionts hosted, subsequently increasing plant growth. I tested mechanisms within this framework using stabilized polyploids of Medicago sativa by asking whether polyploids had greater niche breadth of rhizobial symbionts, produced more or larger nodules, and increased host benefit from the mutualism relative to diploids. I conducted single inoculations of 5 diploid and 5 tetraploid wild populations of M. sativa using 21 strains spanning the Sinorhizobium phylogeny. Tetraploid M. sativa plants produced larger nodules and more shoot biomass than diploids when controlling for the effects of ploidy on plant size. To isolate the direct effects of polyploidy on the legume-rhizobia mutualism, we created neopolyploid M. sativa plants and compared them to their diploid progenitors. Single inoculations of three Sinorhizobium strains were conducted and confocal microscopy was used to determine whether polyploidy immediately alters the internal structure of nodules in a manner that increases rhizobial quantity and quality. Overall, this work supports a role of plant polyploidy in enhancing key mutualism traits and host benefit from rhizobial symbioses. More broadly, my research uncovers mechanisms for how polyploidy alters plant-biotic interactions, thus contributing to ecological and evolutionary theory.
Wednesday, February 14, 2018
A219B Langley Hall
12:00 PM Seminar