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Plants have evolved numerous adaptive developmental and metabolic responses to cope with growth in conditions of limited phosphate (Pi). Regulation of these Pi starvation responses (PSR) at the organism level involves not only cellular Pi perception in different organs, but also inter-organ communication of Pi levels via systemic signaling. Here we summarize recent discoveries on Pi starvation sensing and signaling, with special emphasis on structure-function studies that showed a role for inositol polyphosphates (InsP) as intracellular Pi signals, and on genomic studies that identified a large number of mRNAs with inter-organ mobility, which provide an immense source of potential systemic signals in the control of PSR and other responses., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Throughout evolution, plants have evolved sophisticated adaptive responses that allow them to grow with a limited supply of phosphate, the preferential form in which the essential macronutrient phosphorus is absorbed by plants. Most of these responses are aimed to increase phosphate availability and acquisition through the roots, to optimize its usage in metabolic processes, and to protect plants from the deleterious effects of phosphate deficiency stress. Regulation of these adaptive responses requires fine perception of the external and internal phosphate levels, and a complex signal transduction pathway that integrates information on the phosphate status at the whole-plant scale. The molecular mechanisms that participate in phosphate homeostasis include transcriptional control of gene expression, RNA silencing mediated by microRNAs, regulatory non-coding RNAs of miRNA activity, phosphate transporter trafficking, and post-translational modification of proteins, such as phosphorylation, sumoylation and ubiquitination. Such a varied regulatory repertoire reflects the complexity intrinsic to phosphate surveying and signaling pathways. Here, we describe these regulatory mechanisms, emphasizing the increasing importance of ubiquitination in the control of phosphate starvation responses., (© 2013 Institute of Botany, Chinese Academy of Sciences.)