The nodulation and nyctinastic leaf movement is orchestrated by clock gene LHY inMedicago truncatula

As sessile organisms, plants perceive, respond, and adapt to the environmental changes for optimal growth and survival. The plant growth and fitness are enhanced by circadian clocks through coordination of numerous biological events. In legume species, nitrogen-fixing root nodules were developed as the plant organs specialized for symbiotic transfer of nitrogen between microsymbiont and host. Here, we report that the endogenous circadian rhythm in nodules is regulated byMtLHYin legume speciesMedicago truncatula. Loss of function ofMtLHYleads to a reduction in the number of nodules formed, resulting in a diminished ability to assimilate nitrogen. The operation of the 24-h rhythm in shoot is further influenced by the availability of nitrogen produced by the nodules, leading to the irregulated nyctinastic leaf movement and reduced biomass inmtlhymutants. These data shed new light on the roles ofMtLHYin the orchestration of circadian oscillator in nodules and shoots, which provides a mechanistic link between nodulation, nitrogen assimilation, and clock function.