Crosstalk between brassinosteroid signaling and variable nutrient environments.

Brassinosteroid (BR) represents a group of steroid hormones that regulate plant growth and development as well as environmental adaptation. The fluctuation of external nutrient elements is a situation that plants frequently face in the natural environment, in which nitrogen (N) and phosphorus (P) are two of the most critical nutrients restraint of the early growth of plants. As the macronutrients, N and P are highly required by plants, but their availability or solubility in the soil is relatively low. Since iron (Fe) and P always modulate each other's content and function in plants mutually antagonistically, the regulatory mechanisms of Fe and P are inextricably linked. Recently, BR has emerged as a critical regulator in nutrient acquisition and phenotypic plasticity in response to the variable nutrient levels in Arabidopsis and rice. Here, we review the current understanding of the crosstalk between BR and the three major nutrients (N, P, and Fe), highlighting how nutrient signaling regulates BR synthesis and signaling to accommodate plant growth and development in Arabidopsis and rice.