Annual Plant Reviews Volume 48 -- Contents -- List of Contributors -- Preface -- Section I Introduction -- 1 Phosphorus: Back to the Roots -- 1.1 Introduction -- 1.2 Phosphorus or phosphorous? -- 1.3 Phosphorus on a geological time scale -- 1.4 Phosphorus as an essential, but frequently limiting, soil nutrient for plant productivity -- 1.5 Soil phosphorus pools -- 1.6 Soil phosphorus mobility -- 1.7 Factors determining rates of phosphorus uptake by roots -- 1.8 Phosphorus-starvation responses: does phosphorus homeostasis exist? -- 1.9 Concluding remarks -- Acknowledgements -- References -- Section II P-sensing, transport, and metabolism -- 2 Sensing, signalling, and control of phosphate starvation in plants: molecular players and applications -- 2.1 Introduction -- 2.2 The plant phosphate-starvation response -- 2.3 Sensing of phosphate and other macronutrient limitations in plants -- 2.3.1 Nutrient transporters as sensors/receptors -- 2.3.2 Local Pi sensing and signalling at the root tip by PDR2/LPR1 -- 2.3.3 Phosphite, a tool to investigate P-sensing/signalling -- 2.4 Signalling of phosphate limitation -- 2.4.1 The role of phytohormones -- 2.4.2 Systemic signalling during P-starvation -- 2.4.3 Transcriptional regulators involved in P-signalling and affecting P-starvation responses -- 2.4.4 The role of microRNAs and targeted protein degradation in P-signalling -- 2.4.5 Additional regulators of P-signalling -- 2.5 Improving plant P-acquisition and -utilization efficiency: approaches and targets -- 2.6 Concluding remarks -- References -- 3 'Omics' Approaches Towards Understanding Plant Phosphorus Acquisition and Use -- 3.1 Introduction -- 3.2 Towards a transcriptomics-derived 'phosphatome' -- 3.3 Pi deficiency-induced alterations in the proteome -- 3.4 Core PSR proteins.

3.5 Membrane lipid remodelling: insights from the transcriptome, the proteome, and the lipidome -- 3.6 Genome-wide histone modifications in Pi-deficient plants -- 3.7 Conclusions and outlook -- 3.8 Acknowledgements -- References -- 4 The Role of Post-Translational Enzyme Modifications in the Metabolic Adaptations of Phosphorus-Deprived Plants -- 4.1 Introduction -- 4.2 In the beginning there was protein phosphorylation -- 4.3 Monoubiquitination has emerged as a crucial PTM that interacts with phosphorylation to control the function of diverse proteins -- 4.4 Post-translational modification of plant phosphoenolpyruvate carboxylase by phosphorylation versus monoubiquitination -- 4.4.1 Activation of PEP carboxylase by in-vivo phosphorylation appears to be a universal aspect of the plant P-starvation response -- 4.4.2 PEP carboxylase monoubiquitination: an old dog learns new tricks -- 4.4.3 Reciprocal control of PEP carboxylase by in-vivo monoubiquitination and phosphorylation in developing proteoid roots of P-deficient harsh hakea -- 4.5 Glycosylation is a sweet PTM of glycoproteins -- 4.5.1 A pair of AtPAP26 glycoforms is upregulated and secreted by P-deprived Arabidopsis -- 4.5.2 The AtPAP26-S2 glycoform copurifies with, and appears to interact with, a curculin-like lectin -- 4.6 Concluding remarks -- Acknowledgements -- References -- 5 Phosphate Transporters -- 5.1 Introduction -- 5.2 The PHT1 transporters -- 5.2.1 PHT1 structure, activity, and expression patterns -- 5.3 Control of PHT1 activity -- 5.3.1 Control of PHT1 transcript levels -- 5.3.2 Post-transcriptional control of PHT1 -- 5.4 PHO1 and phosphate export -- 5.4.1 PHO1 structure, activity, and expression patterns -- 5.4.2 Transcriptional control of PHO1 expression -- 5.4.3 Post-transcriptional control of PHO1 -- 5.5 Phosphate transporters of organelles.

5.5.1 Mitochondrial phosphate transporters -- 5.5.2 Plastidial phosphate transporters -- 5.5.3 The role of PHT2 in plastid phosphate transport -- 5.5.4 The role of PHT4 in plastid phosphate transport -- 5.6 Phosphate transporters of other organelles -- 5.6.1 Golgi phosphate transporters -- 5.6.2 Peroxisomal phosphate transporters -- 5.6.3 Vacuolar (tonoplast) phosphate transporters -- 5.7 Concluding remarks -- Acknowledgements -- References -- 6 Molecular Components that Drive Phosphorus-Remobilisation During Leaf Senescence -- 6.1 Introduction -- 6.2 Transcriptomes of senescence and phosphate-deficiency -- 6.3 Major biochemical components that mediate P-remobilisation during leaf senescence -- 6.3.1 Nucleases -- 6.3.2 Phosphatases -- 6.3.3 Lipid-remodelling enzymes -- 6.3.4 Pi transporters -- 6.4 Regulatory and signalling components of senescing leaves -- 6.4.1 Transcription factors -- 6.4.2 The SPX superfamily -- 6.4.3 Ubiquitination components and miRNAs -- 6.5 Role of hormones during leaf senescence -- 6.5.1 Ethylene and strigolactones -- 6.5.2 Abscisic acid -- 6.5.3 Cytokinins -- 6.6 Concluding remarks -- Acknowledgements -- References -- 7 Interactions between Nitrogen and Phosphorus metabolism -- 7.1 Introduction -- 7.2 Roles of N and P in plants and the extent to which compounds containing N or P can be substituted by compounds lacking N or P -- 7.3 Variability in the N:P ratio in plants and its metabolic and ecological significance -- 7.3.1 Fixed N:P ratios: the role of compounds containing both N and P -- 7.3.2 Protein:RNA ratio, organism N:P ratio, the Growth Rate Hypothesis -- 7.3.3 Organism N and P concentration as a function of external supply of N and P -- 7.3.4 Conclusions -- 7.4 Interactions in N and P acquisition and assimilation -- 7.4.1 Structures involved in acquisition of N and P.

7.4.2 Secretion of enzymes and organic anions facilitates root N and P acquisition -- 7.5 Protein synthesis and protein degradation during P-deprivation: significance for N-P interaction -- 7.6 General conclusions -- Acknowledgements -- References -- Section III P-deprivation responses -- 8 Metabolomics of plant phosphorus-starvation response -- 8.1 Introduction -- 8.2 Metabolomic approaches -- 8.3 Metabolomic analysis platforms -- 8.4 Data analysis -- 8.5 Metabolomics strategies directed at dissecting responses to P starvation -- 8.6 Opportunities for metabolomics to contribute to the development of P-efficient crops -- 8.7 Future prospects -- Acknowledgements -- References -- 9 Membrane remodelling in phosphorus-deficient plants -- 9.1 Introduction -- 9.2 Membrane lipid remodelling during phosphate deprivation -- 9.3 Monogalactosyldiacylglycerol (MGDG) -- 9.4 Digalactosyldiacylglycerol (DGDG) -- 9.5 Sulfolipid (SQDG) and glucuronosyldiacylglycerol (GlcADG) -- 9.6 Phospholipid degradation by phospholipase D and phosphatidate phosphatase -- 9.7 Phospholipase C (PLC) -- 9.8 Acyl hydrolases -- 9.9 Lipid trafficking under phosphate starvation -- 9.10 Glucosylceramide, sterol glucoside, and acylated sterol glucoside -- 9.11 The role of auxin in remodelling of membrane lipid composition -- 9.12 Improved Pi status by symbiosis with arbuscular mycorrhizal fungi -- 9.13 Outlook -- References -- 10 The Role of Intracellular and Secreted Purple Acid Phosphatases in Plant Phosphorus Scavenging and Recycling -- 10.1 Introduction -- 10.2 Bioinformatics and structural analysis of plant PAPs -- 10.2.1 PAP bioinformatics -- 10.2.2 Structural biochemistry of plant PAPs -- 10.3 Biochemical characterisation of plant PAPs -- 10.4 Diverse subcellular localisation of plant PAPs -- 10.5 Transcriptional and post-transcriptional regulation of PAP expression by P availability.

10.5.1 Complex signal transduction pathways integrate nutritional P status with PAP expression -- 10.5.2 Post-translational PAP modification -- 10.6 Functional analysis of PAPs involved in P mobilisation and utilisation -- 10.7 Perspectives -- Acknowledgements -- References -- 11 Metabolic Adaptations of the Non-Mycotrophic Proteaceae to Soils With Low Phosphorus Availability -- 11.1 Introduction -- 11.2 Phosphorus nutrition of Proteaceae, with a focus on south-western Australia -- 11.2.1 Phosphorus acquisition by non-mycorrhizal roots: cluster roots -- 11.2.2 Proteaceae species that do not produce cluster roots -- 11.2.3 Phosphorus toxicity -- 11.2.4 High rates of photosynthesis despite low leaf P concentrations -- 11.2.5 Leaf longevity -- 11.2.6 Delayed greening -- 11.2.7 Efficient and proficient P remobilisation from senescing organs -- 11.2.8 Seed P reserves -- 11.3 Comparison of species of Proteaceae in south-western Australia with species elsewhere -- 11.3.1 The Cape Floristic Region in South Africa -- 11.3.2 Eastern Australia -- 11.3.3 Southern South America -- 11.3.4 Brazil -- 11.4 Perspectives -- Acknowledgements -- References -- 12 Algae in a phosphorus-limited landscape -- 12.1 Introduction -- 12.2 P-deprivation responses of green algae and vascular plants -- 12.2.1 Phosphatases -- 12.2.2 Nucleases -- 12.2.3 Pi transport -- 12.2.4 Polyphosphates -- 12.2.5 Phospholipids -- 12.3 Control of P deprivation responses -- 12.3.1 PSR1-dependent gene expression in P-starved algae -- 12.3.2 Low-phosphate bleaching mutants -- 12.4 Future prospects -- Acknowledgements -- References -- Section IV Significance of plant-microbe interactions for P-acquisition and metabolism -- 13 Impact of roots, microorganisms and microfauna on the fate of soil phosphorus in the rhizosphere -- 13.1 Introduction -- 13.2 Spatial extension of the rhizosphere.

13.2.1 Root architecture and growth.