Post Doctoral Associate University of Miami Miami, Florida
Body of Abstract: One of the challenges facing current fertilizer-dependent food production is the limited availability of phosphorus (P), an essential macronutrient for plant growth that significantly affects crop productivity. Fortunately, most plants have evolved to overcome P limitation by symbiotically associating with arbuscular mycorrhizal (AM) fungi. AM fungi provide plants with mineral nutrients (mainly P but also others) in exchange for carbon provided by the host. However, the mechanisms allowing plants to maintain an optimal cost-benefit balance during this intimate relationship remain elusive. In this study, we investigate the role of the M. truncatula CLAVATA1-like receptor-like kinase SUNN in the integration of nutrients and symbiotic signals. The sunn mutant has been found to be associated with the regulation of AM symbiosis and shows hypercolonization by AM fungi. Our findings suggest that SUNN also has a role in lateral root and shoot development. Compared to the wildtype, sunn mutants are taller with a higher number of lateral roots. Interestingly, when inoculated with two different AM fungal strains, sunn showed differential regulation of some of the key symbiotic pathway genes such as PT4, RAM1, and D27. Phosphate, which is the major driver of symbiosis is also affected by other micronutrients, particularly iron (Fe), which negatively impacts P availability. We found that when challenged with excess Fe, wildtype roots showed enhanced AM fungal colonization. By contrast, colonization in sunn roots remained unchanged. These observations indicate that SUNN represents a candidate for a major player in the integration of various nutrient and symbiotic signals. Deciphering SUNN role in this process is critical for harnessing the benefits of plant-microbe interactions and achieving agricultural sustainability.