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: 3.45). 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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    ABSTRACT: Phosphorus (P), in the form of phosphate ion (Pi), is a vital element contributing in biomolecule structures, metabolic reactions, signaling pathways and energy transfer within the living cells. The objective of the present study was to assess the influence of fungal infection on Pi metabolism in compare to the effects of phosphate stress in Arabidopsis. Quantification of total P contents showed higher storage of P in the shoots than in the roots of Pi-fed plants, while the homeostatic levels of soluble Pi was kept in a fairly narrow range in roots and shoots of both Pi-fed and Pi-starved. When the plants were subjected to Pi starvation, both total P and soluble Pi contents were reduced to minimal levels in roots and shoots. Total acid phosphatase (APase) activity was also affected by the level of available Pi such that it was higher in the starved plants than in the fed plants. When Pi-fed plants were subjected to fungal infections, a remarkable reduction was observed for the above indicators in roots but not shoots. Surprisingly, the analysis of APase expression profiling after inoculation with Alternaria brassicicola showed that the rates of transcription of several APase-encoding genes were affected by fungus infection. Atpap9, a fungal inducible gene, promoter analysis also indicated alterations in tissue-specific expression patterns upon the fungal infections. These data clearly illustrate that how a nutrient distribution is affected by environmental conditions, even regardless of available phosphate.
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    ABSTRACT: Phosphorus (P) is an essential macronutrient for plant growth and development. Several genes involved in phosphorus deficiency stress have been identified in various plant species. However, a whole genome understanding of the molecular mechanisms involved in plant adaptations to low P remains elusive, and there is particularly little information on the genetic basis of these acclimations in coniferous trees. Masson pine (Pinus massoniana) is grown mainly in the tropical and subtropical regions in China, many of which are severely lacking in inorganic phosphate (Pi). In previous work, we described an elite P. massoniana genotype demonstrating a high tolerance to Pi-deficiency.
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    ABSTRACT: Despite the abundance of phosphorus in soil, very little is available as phosphate (Pi) for plants. Plants often experience low Pi (LP) stress. Intensive studies have been conducted to reveal the mechanism used by plants to deal with LP; however, Pi sensing and signal transduction pathways are not fully understood. Using in-gel kinase assays, we determined the activities of MPK3 and MPK6 in Arabidopsis thaliana seedlings under both LP and Pi-sufficient (Murashige and Skoog, MS) conditions. Using MKK9 mutant transgenic and crossed mutants, we analyzed the functions of MPK3 and MPK6 in regulating Pi responses of seedlings. The regulation of Pi responses by downstream components of MKK9-MPK3/MPK6 was also screened. LP treatment activated MPK3 and MPK6. Under both LP and MS conditions, mpk3 and mpk6 seedlings took up and accumulated less Pi than the wild-type; activation of MKK9-MPK3/MPK6 in transgenic seedlings induced the transcription of Pi acquisition-related genes and enhanced Pi uptake and accumulation, whereas its activation suppressed the transcription of anthocyanin biosynthetic genes and anthocyanin accumulation; WRKY75 was downstream of MKK9-MPK3/MPK6 when regulating the accumulation of Pi and anthocyanin, and the transcription of Pi acquisition-related and anthocyanin biosynthetic genes. These results suggest that the MKK9-MPK3/MPK6 cascade is part of the Pi signaling pathway in plants.
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