Phosphate starvation responses in crop roots: from well-known players to novel candidates

Phosphorus (P) is a major essential macronutrient for plants, and its availability in the soil is scarce and not renewable. Molecular responses to low concentrations of inorganic phosphate (Pi) are better understood in Arabidopsis, whereas several information gaps still exist in crops. In addition, rice has invaluable socio-economic importance and is a crop model system for studies on Pi starvation responses due to its high tolerance to Pi deprivation. Thus, unraveling the mechanisms related to Pi starvation in rice is extremely important for plant breeding and agronomic productivity and sustainability. In this review, we discuss the recent progress and remaining gaps of knowledge on the molecular mechanisms of sensing and signaling Pi starvation in rice. By exploring publicly available transcriptomic data, we propose new functions on Pi metabolism for previously known genes and pinpoint attention-worthy genes with unknown function, although evidently regulated under Pi starvation. Orthologs of the promising Pi-responsive genes with unclear function identified in rice roots were also discussed in the context of other crops. New strategies to increase global food productivity by improving Pi uptake in rice and possibly in other crops are proposed.