Abstract
Phosphate (P
i
) deficiency is a critical environmental constraint that affects the growth and development of several legume crops that are usually cultivated in semi-arid regions and marginal areas. P
i
deficiency is known to be a significant limitation for symbiotic nitrogen (N
2
) fixation (SNF), and variability in SNF is strongly interlinked with the concentrations of P
i
in the nodules. To deal with P
i
deficiency, plants trigger various adaptive responses, including the induction and secretion of acid phosphatases, maintenance of P
i
homeostasis in nodules and other organs, and improvement of oxygen (O
2
) consumption per unit of nodule mass. These molecular and physiological responses can be observed in terms of changes in growth, photosynthesis, and respiration. In this mini review, we provide a brief introduction to the problem of P
i
deficiency in legume crops. We then summarize the current understanding of how P
i
deficiency is regulated in legumes by changes in the transcriptomes and metabolomes found in different plant organs. Finally, we will provide perspectives on future directions for research in this field.