Proteins containing an SPX domain are involved in numerous aspects of phosphate homeostasis and the response to phosphate deficiency.SPX4 is known to bind to the transcription factor PHR2 in the presence of inositol polyphosphate,affecting its ability to activate the expression of phosphate-starvation-induced (PSI) genes.Plants have evolved mechanisms to coordinate the uptake and utilization of phosphate and nitrate.Two recent works (Hu et al.,2019;Ruan et al.,2019) have identified different E3 ubiquitin ligases that mediate the degradation of SPX4 under either phosphate-deficient conditions or nitrate-replete conditions.These studies highlight the potential of SPX proteins,E3 ubiquitin ligases,and inositol polyphosphate to regulate distinct nutrient signaling pathways in a coordinated fashion.