Long-distance call from phosphate: systemic regulation of phosphate starvation responses

Abstract

Phosphate (Pi) is an essential nutrient for plants but is normally fixed in soil, which limits plant growth and reproduction. In response to low availability of Pi, shoots and roots react differently but cooperatively to improve Pi acquisition from the rhizosphere and adjust Pi distribution and metabolism within plants. Shoot and root responses are coordinated by the trafficking of various kinds of systemic signals through the vasculature. Mutual communication between different tissues is necessary to integrate the environmental stimuli with the internal cues at the whole-plant level. Different approaches have been used to monitor or manipulate components in the vascular stream to reveal several candidates of systemic signals from roots or shoots, including photosynthates, phytohormones, microRNAs, and Pi. In addition, the downstream signalling pathways mediated by these signals have been discovered. The crosstalk among different signalling pathways has been revealed, showing the complexity of the Pi signalling network. In this review, we summarize the approaches used for studying systemic signalling and discuss recent progress and challenges in investigating the systemic signalling pathway that integrates Pi starvation responses to maintain Pi at physiological concentrations. Knowledge gained from this study may help improve the phosphorus use efficiency of crops.

The EXS Domain of PHO1 Participates in the Response of Shoots to Phosphate Deficiency via a Root-to-Shoot Signal

“…It is possible that the expression of the EXS-GFP domain in roots influences shoot growth via changes in proteins or metabolites transported from roots to shoots that are not reflected at the level of the root gene expression profile. Alternatively, it is possible that an alteration of a shoot-to-root signal in the EXS lines leads to changes in root transcript (Lin et al, 2014). Nevertheless, a few interesting observations can be made from inspection of the root transcriptome.…”

Effects of phosphorus application on photosynthetic carbon and nitrogen metabolism, water use efficiency and growth of dwarf bamboo ( Fargesia rufa ) subjected to water deficit

“…Recent studies have demonstrated that P deficiency inhibits processes related to energy metabolism and biochemical synthesis, such as photosynthesis, respiration (especially the glycolytic pathway) and N fixation; P deficiency also reduces the activities of key enzymes involved in C and N metabolism dos Santos et al, 2004;Burman et al, 2009). Moreover, P deficiency causes aberrant root architecture in terms of number and density of lateral roots, and thus affects P i transport, which serves as a long-distance signal (Lin et al, 2014). Consequently, P is considered the most important element limiting plant growth.…”

The regulation and plasticity of root hair patterning and morphogenesis

“…Pi is an essential plant nutrient and its deficiency leads to deleterious effects on plant development and growth. Pi signaling and homeostasis in plants is reviewed elsewhere (Chiou and Lin, 2011;Lin et al, 2014;Briat et al, 2015) and here we focus on the response to Pi deficiency. The Pi starvation response (PSR) is a multifaceted adaptation that aims to improve Pi acquisition and the internal recycling of Pi.…”

“…In addition, root architectural changes, comprising restricted elongation of primary roots, an increase in the density and length of lateral roots, and the formation of denser and longer root hairs, lead collectively to an increase in the absorptive area, particularly in the Pi-rich topsoil layer. The coordination of shoot and root responses involves trafficking of systemic signals, such as sugar, microRNAs and hormones, through the vasculature to tune the responses in roots (Lin et al, 2014). The morphological responses of roots are thought to be chiefly controlled by the local concentration of Pi (Ticconi et al, 2004;Thibaud et al, 2010), but it may be assumed that local and systemic signals are integrated and that long distance signals might also influence some or all root morphological responses.…”