Replace, reuse, recycle: improving the sustainable use of phosphorus by plants

Abstract

The 'phosphorus problem' has recently received strong interest with two distinct strands of importance. The first is that too much phosphorus (P) is entering into waste water, creating a significant economic and ecological problem. Secondly, while agricultural demand for phosphate fertilizer is increasing to maintain crop yields, rock phosphate reserves are rapidly declining. Unravelling the mechanisms by which plants sense, respond to, and acquire phosphate can address both problems, allowing the development of crop plants that are more efficient at acquiring and using limited amounts of phosphate while at the same time improving the potential of plants and other photosynthetic organisms for nutrient recapture and recycling from waste water. In this review, we attempt to synthesize these important but often disparate parts of the debate in a holistic fashion, since solutions to such a complex problem require integrated and multidisciplinary approaches that address both P supply and demand. Rapid progress has been made recently in our understanding of local and systemic signalling mechanisms for phosphate, and of expression and regulation of membrane proteins that take phosphate up from the environment and transport it within the plant. We discuss the current state of understanding of such mechanisms involved in sensing and responding to phosphate stress. We also discuss approaches to improve the P-use efficiency of crop plants and future direction for sustainable use of P, including use of photosynthetic organisms for recapture of P from waste waters.

Eukaryotic Phosphate Homeostasis: The Inositol Pyrophosphate Perspective

“…The benefits (high yield) and drawbacks (limited reserves of phosphate rock, pollution) that arise from the usage of phosphate fertilizers have divided opinion over time [19]. This has led to concerted global efforts to understand the molecular mechanisms of phosphate homeostasis in plants.…”

The varied functions of aluminium-activated malate transporters–much more than aluminium resistance

“…In these soils, aluminium ions become solubilized and damage crops via root growth inhibition [13] and, to compound the problem, nutrients such as phosphate become less available [14]. Several plant species have been identified as aluminium-resistant and they use a variety of mechanisms including thickening of cell walls [15], active transport of aluminium away from sensitive organs [16], or, prominently, organic acid exudation, chiefly either by release of malate or citrate [17,18].…”

“…In addition to protection from Al 3+ toxicity, malate extrusion has the benefit of increasing phosphate availability in the soil–since Al 3+ binds and complexes phosphate [22]. This is part of a host of processes activated in plants for improved phosphorous usage [14,23]. Heterologous expression of Ta ALMT1 in cultured tobacco cells, Xenopus oocytes, and transgenic rice plants has shown efflux of malate activated by the presence of Al 3+ and expression confers Al-resistance to tobacco cells [2].…”

Transcriptome Characterization of the Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook.) and Expression Analysis of Candidate Phosphate Transporter Genes

“…Thus, the PHT1s were the most important transporters for plants and widely studied in many plants like tomato, rice, and poplar [19,22]. The other PHT family members are mostly responsible for intracellular P distribution [61]. The PHT2s play the function of H + /Pi cotransporters in the plastids of plants, the PHT3s were recognized as mitochondrial Pi transporter genes to catalyze the exchange of Pi between the matrix and cytosol, and the PHT4s were reported to transport Pi in plastids and the Golgiapparatus [21,61].…”