Article

Regulation of phosphate starvation responses in higher plants

School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia.
Annals of Botany (Impact Factor: 3.65). 02/2010; 105(4):513-26. DOI: 10.1093/aob/mcq015
Source: PubMed

ABSTRACT

Phosphorus (P) is often a limiting mineral nutrient for plant growth. Many soils worldwide are deficient in soluble inorganic phosphate (P(i)), the form of P most readily absorbed and utilized by plants. A network of elaborate developmental and biochemical adaptations has evolved in plants to enhance P(i) acquisition and avoid starvation.
Controlling the deployment of adaptations used by plants to avoid P(i) starvation requires a sophisticated sensing and regulatory system that can integrate external and internal information regarding P(i) availability. In this review, the current knowledge of the regulatory mechanisms that control P(i) starvation responses and the local and long-distance signals that may trigger P(i) starvation responses are discussed. Uncharacterized mutants that have P(i)-related phenotypes and their potential to give us additional insights into regulatory pathways and P(i) starvation-induced signalling are also highlighted and assessed.
An impressive list of factors that regulate P(i) starvation responses is now available, as is a good deal of knowledge regarding the local and long-distance signals that allow a plant to sense and respond to P(i) availability. However, we are only beginning to understand how these factors and signals are integrated with one another in a regulatory web able to control the range of responses demonstrated by plants grown in low P(i) environments. Much more knowledge is needed in this agronomically important area before real gains can be made in improving P(i) acquisition in crop plants.

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Available from: Patrick M. Finnegan, May 11, 2014
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    • "In addition, Pi-starved plants can regulate multiple metabolic processes to reprioritize utilization of internal Pi and maximize acquisition of external Pi to adapt to low Pi environments (Vance et al., 2003; Wissuwa, 2003). The complex network of regulatory genes necessary to sense and respond to Pi deficiency is being dissected (Smith et al., 2010; Yang and Finnegan, 2010; Hammond and White, 2011; Kuo and Chiou, 2011). For example, in Arabidopsis thaliana, a major transcriptional regulatory system that involves PHR1, SIZ1, miR399 and PHO2 in response to Pi deficiency has been identified (Rubio et al., 2001; Fujii et al., 2005; Aung et al., 2006; Schachtman and Shin, 2007). "
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    ABSTRACT: The WRKY transcription factor family has 109 members in the rice genome, and has been reported to be involved in the regulation of biotic and abiotic stress in plants. Here, we demonstrated that a rice OsWRKY74 belonging to group III of the WRKY transcription factor family was involved in tolerance to phosphate (Pi) starvation. OsWRKY74 was localized in the nucleus and mainly expressed in roots and leaves. Overexpression of OsWRKY74 significantly enhanced tolerance to Pi starvation, whereas transgenic lines with down-regulation of OsWRKY74 were sensitive to Pi starvation. Root and shoot biomass, and phosphorus (P) concentration in rice OsWRKY74-overexpressing plants were ~16% higher than those of wild-type (WT) plants in Pi-deficient hydroponic solution. In soil pot experiments, >24% increases in tiller number, grain weight and P concentration were observed in rice OsWRKY74-overexpressing plants compared to WT plants when grown in P-deficient medium. Furthermore, Pi starvation-induced changes in root system architecture were more profound in OsWRKY74-overexpressing plants than in WT plants. Expression patterns of a number of Pi-responsive genes were altered in the OsWRKY74-overexpressing and RNA interference lines. In addition, OsWRKY74 may also be involved in the response to deficiencies in iron (Fe) and nitrogen (N) as well as cold stress in rice. In Pi-deficient conditions, OsWRKY74-overexpressing plants exhibited greater accumulation of Fe and up-regulation of the cold-responsive genes than WT plants. These findings highlight the role of OsWRKY74 in modulation of Pi homeostasis and potential crosstalk between P starvation and Fe starvation, and cold stress in rice.
    Full-text · Article · Dec 2015 · Journal of Experimental Botany
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    • "Because of their importance for plant acclimation to low-Pi, numerous genetic studies have been done over the past 15 yr. Nevertheless, only few elements of these local and systemic signalling pathways have been unveiled (Yang & Finnegan, 2010; Abel, 2011). Some transcription factors have been found controlling some of the Pi-starvation responses. "
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    ABSTRACT: Plants display numerous strategies to cope with phosphate (Pi)-deficiency. Despite multiple genetic studies, the molecular mechanisms of low-Pi-signalling remain unknown. To validate the interest of chemical genetics to investigate this pathway we discovered and analysed the effects of PHOSTIN (PSN), a drug mimicking Pi-starvation in Arabidopsis. We assessed the effects of PSN and structural analogues on the induction of Pi-deficiency responses in mutants and wild-type and followed their accumulation in plants organs by high pressure liquid chromotography (HPLC) or mass-spectrophotometry. We show that PSN is cleaved in the growth medium, releasing its active motif (PSN11), which accumulates in plants roots. Despite the overaccumulation of Pi in the roots of treated plants, PSN11 elicits both local and systemic Pi-starvation effects. Nevertheless, albeit that the transcriptional activation of low-Pi genes by PSN11 is lost in the phr1;phl1 double mutant, neither PHO1 nor PHO2 are required for PSN11 effects. The range of local and systemic responses to Pi-starvation elicited, and their dependence on the PHR1/PHL1 function suggests that PSN11 affects an important and early step of Pi-starvation signalling. Its independence from PHO1 and PHO2 suggest the existence of unknown pathway(s), showing the usefulness of PSN and chemical genetics to bring new elements to this field. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
    Full-text · Article · Aug 2015 · New Phytologist
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    • "transcription factor WRKY75 and SPX1 proteins) (Yang and Finnegan, 2010) on PSR. PHO2 was confirmed to be a target gene for the microRNA miR399 having miR399 target sites in the 5-untranslated region of its transcripts (Yang and Finnegan, 2010). The MYB transcription factor PHR1 was the first molecular determinant shown to be required for Pi starvation-dependent responses. "
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    ABSTRACT: Changes in resource (mineral nutrients and water) availability, due to their heterogeneous distribution in space and time, affect plant development. Plants need to sense these changes to optimize growth and biomass allocation by integrating root and shoot growth. Since a limited supply of water or nutrients can elicit similar physiological responses (the relative activation of root growth at the expense of shoot growth), similar underlying mechanisms may affect perception and acquisition of either nutrients or water. This review compares root and shoot responses to availability of different macronutrients and water. Attention is given to the roles of root-to-shoot signalling and shoot-to-root signalling, with regard to coordinating changes in root and shoot growth and development. Involvement of plant hormones in regulating physiological responses such as stomatal and hydraulic conductance is revealed by measuring the effects of resource availability on phytohormone concentrations in roots and shoots, and their flow between roots and shoots in xylem and phloem saps. More specific evidence can be obtained by measuring the physiological responses of genotypes with altered hormone responses or concentrations. We discuss the similarity and diversity of changes in shoot growth, allocation to root growth, and root architecture under changes in water, nitrate, and phosphorous availability, and the possible involvement of abscisic acid, indole-acetic acid, and cytokinin in their regulation. A better understanding of these mechanisms may contribute to better crop management for efficient use of these resources and to selecting crops for improved performance under suboptimal soil conditions. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.
    Full-text · Article · Feb 2015 · Journal of Experimental Botany
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