Genetic and functional diversity of Lotus SymRK homologous receptor kinases in root endosymbiosis
High yields in crops are equated with the use of fertilizers, while plants have developed their own solutions to nutrient deficiencies. For example, legume roots accommodate microorganisms, forming root endosymbiosis. Arbuscular Mycorrhiza (AM) formed with Glomeromycota fungi and Root Nodule Symbiosis (RNS) formed with nitrogen-fixing bacteria facilitate the acquisition of essential nutrients such as phosphate from the soil and the fixation of atmospheric dinitrogen, respectively. Despite their morphological and physiological differences, AM and RNS share a set of common symbiosis genes conserved in plants. These genes are essential for cell developmental programmes leading to intracellular accommodation of endosymbionts and include the membrane-bound Symbiosis Receptor Kinase (SymRK). SymRK, is a member of the Malectin-Like Domain Leucine-Rich Repeat Receptor Kinase (MLD-LRR-RK) family and is indispensable for epidermal infection of AM fungi and rhizobia bacteria. Since these symbioses develop largely in tissues below the epidermis, where SymRK does not appear to be essential, we hypothesized that other members of this uncharacterised gene family may also be involved in controlling symbiotic host cell development. To explore this hypothesis, we identified a family of SymRK Homologous Receptor-Like Kinases (SHRKs) in the model legume Lotus japonicus. In a first preliminary genetic survey, we observed that knockout of individual SHRKs potentially leads to at least three distinct phenotypes in AM or RNS, revealing functionally distinct sub-categories within this receptor subfamily. This project aims to uncover the molecular details responsible for this functional diversification. We anticipate unravelling novel regulatory hubs for symbiotic accommodation of AM fungi or rhizobia bacteria and assessing the genetic differences underlying their quantitative contribution to symbiosis.
Principal Investigator: Dr. Kate Parys, Institute of Genetics, Ludwig-Maximilians-Universität Munich