Macronutrient elements including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) are required in relatively large and steady amounts for plant growth and development. Deficient or excessive supply of macronutrients from external environments may trigger a series of plant responses at phenotypic and molecular levels during the entire life cycle. Among the intertwined molecular networks underlying plant responses to macronutrient stress, noncoding RNAs (ncRNAs), mainly microRNAs (miRNAs) and long ncRNAs (lncRNAs), may serve as pivotal regulators for the coordination between nutrient supply and plant demand, while the responsive ncRNA-target module and the interactive mechanism vary among elements and species. Towards a comprehensive identification and functional characterization of nutrient-responsive ncRNAs and their downstream molecules, high-throughput sequencing has produced massive omics data for comparative expression profiling as a first step. In this review, we highlight the recent findings of ncRNA-mediated regulation in response to macronutrient stress, with special emphasis on the large-scale sequencing efforts for screening out candidate nutrient-responsive ncRNAs in plants, and discuss potential improvements in theoretical study to provide better guidance for crop breeding practices.

Phosphorus (P) is an essential nutrient for plants, and its scarcity, especially in the form of soluble phosphate (Pi), induces phosphate starvation responses (PSRs). Our research delves into the molecular mechanisms that regulate tomato (Solanum lycopersicum) plant adaptation to Pi deficiency, highlighting the role of 2 PHOSPHATE STARVATION RESPONSE (PHR) transcription factors, SlPHR3 and SlPHR4, as central regulators of Pi metabolism and related developmental/physiological processes, particularly PSRs. Notably, our investigation into the SlPHR3- and SlPHR4-regulated transcriptional network led to the discovery of 3 previously unidentified regulators of Pi metabolism and PSRs: SlGRAS47, SlBHLH48, and SlMYB28. We substantiated the important roles of SlMYB28 in mediating SlPHR3 and SlPHR4 function by demonstrating that SlMYB28 suppression reduces Pi and P accumulation, ameliorates PSR-related phenotypes, and decreases the expression of genes involved in Pi metabolism and PSRs in SlPHR3 and SlPHR4 overexpression plants. Our findings shed light on the adaptive strategies of plants to Pi starvation and open avenues for the identification of important genes involved in Pi metabolism and PSRs, which can be leveraged to improve Pi use efficiency in agricultural crops.