Metabolomics and Transcriptomics in Legumes Under Phosphate Deficiency in Relation to Nitrogen Fixation by Root Nodules

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.