The nutritional mutualism formed between land plants and arbuscular mycorrhizal (AM) fungi involves intracellular accommodation of the fungal symbiont and relies on concerted cellular reprograming. Maximal physical interaction is achieved during the emergence and development of the arbuscules, creating a hub for nutrient exchange and potentially for plant-fungal communication. Receptor-like kinases (RLKs) allow plant cells to sense and respond to their environment and are crucial for signalling during biotic interactions. A rice RLK, ARBUSCULAR RECEPTOR-LIKE KINASE 1 (OsARK1), had earlier been found to localize specifically to the symbiotic interface of arbusculated cells and its orthologues are present only among AM-competent plant species. In this dissertation, the symbiotic role of OsARK1 was studied using genetics, phylogenetics and cell biology approaches. Mutation in OsARK1 resulted in normal arbuscule development but reduced colonization levels that could be rescued in the presence of a wild-type AM fungal mycelium indicating OsARK1 regulates AM symbiosis after arbuscule formation by maintaining fungal fitness. Phylogenetic analyses of the OsARK1 RLK subfamily showed ARK and SIMILAR PROTEIN TO ARK 1 (SPARK1) as the two members present in non-vascular plants while the paralogues ARK1 and ARK2 arose early in the evolution of tracheophytes. The pattern of occurrence of the newly discovered SPARK domain in the extracellular region of members of this RLK subfamily, named SPARK-I, argues for ARK1 and ARK2 to have coevolved. A rice ark2 mutant displayed a reduced colonization phenotype which was quantitatively different compared to ark1. Global transcriptional signatures of the mutants showed several putative components of common as well as distinctive signalling pathways being regulated by OsARK1 and OsARK2. A global downregulation of hydrolytic enzymes in the mutant backgrounds and alterations in lipid distribution in arbusculated cells suggest these RLKs to be part of an ancient signalling pathway directing post-arbuscule development processes to sustain AM symbiosis.