Arbuscular mycorrhizal fungi (AMF) develop interdependent connections with roots of about 90% of plant species. These interactions increase availability as well as translocation of nutrients (especially N and P), and thereby improve plant nutrition and growth. Moreover, resistance to a variety of stresses, among which salt stress, has been shown to be improved by AMF-plant interactions, for example in rice. Intense research to explain the molecular mechanisms of AMF-plant beneficial interactions led to the identification of phosphate and ammonium transporters involved in nutrient exchanges from AMF to the plant, in several plant species. In spite of the importance of potassium (K+) for plant physiology, the contribution of AMF symbiosis to plant K+ nutrition has been little documented. Over-expression of plant K+ transporters has been described in Lotus japonicus and tomato in condition of AMF symbiosis. Furthermore, K+ transport systems in the AMF Rhizophagus irregularis have been identified in silico. Here, K+ nutrition in rice colonized by R. irregularis has been analyzed at molecular and physiological levels. Surprisingly, major K+ transport systems in rice were down-regulated upon AMF interactions, suggesting strong increase in K+ availability for uptake by root cells in symbiotic conditions. Role of K+ in the relationships between rice and R. irregularis will also be discussed