Dissecting Symbiosis Permissiveness in Parasponia andersonii

Abstract

Nutrient limitations often constrain plant growth, leading to the use of chemical fertilizers, which can harm the environment. Biological nitrogen fixation, involving nitrogen-fixing bacteria in plant roots, provides a sustainable alternative. My research aligns with this goal, focusing on non-legume plants, particularly the non-nodulating Trema orientalis RG33 and the nodulating Parasponia andersonii species. One key gene I investigated was SYMRK, essential for root nodules and AM symbioses in legumes. In T. orientalis RG33, I identified a point mutation in this gene, and when introduced into the P. andersonii SYMRK gene, it did not disrupt the gene's function, successfully restoring both root nodule formation and AM symbiosis in a P. andersonii symrk mutant. I also explored the ectopic expression of NSP2, which enhanced AM mycorrhization but inhibited nodulation in Parasponia. Lastly, I discovered that the autoregulation of nodulation (AON) pathway, which regulates nodule numbers, is conserved in both legumes and non-legumes, providing a promising strategy for engineering nitrogen fixation in non-nodulating plants.