Responses to Deficiencies in Macronutrients

Davies, John P.; Grossman, Arthur R.

doi:10.1007/0-306-48204-5_32

The Molecular Biology of Chloroplasts and Mitochondria in Chlamydomonas

DOI: 10.1007/0-306-48204-5_32

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Responses to Deficiencies in Macronutrients

John P. Davies

Arthur R. Grossman

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Cited by 24 publications

(20 citation statements)

References 163 publications

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“…Increases in O-acetylserine levels appear to occur when Arabidopsis thaliana plants are starved for S or provided with excess N (19). In C. reinhardtii, specific regulatory elements, including SAC1 and SAC3, control S deprivation responses (8)(9)(10). A number of physiological responses of C. reinhardtii to S limitation require the SAC1 protein (8).…”

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Insights into the Survival of Chlamydomonas reinhardtii during Sulfur Starvation Based on Microarray Analysis of Gene Expression

et al. 2004

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Responses of photosynthetic organisms to sulfur starvation include (i) increasing the capacity of the cell for transporting and/or assimilating exogenous sulfate, (ii) restructuring cellular features to conserve sulfur resources, and (iii) modulating metabolic processes and rates of cell growth and division. We used microarray analyses to obtain a genome-level view of changes in mRNA abundances in the green alga Chlamydomonas reinhardtii during sulfur starvation. The work confirms and extends upon previous findings showing that sulfur deprivation elicits changes in levels of transcripts for proteins that help scavenge sulfate and economize on the use of sulfur resources. Changes in levels of transcripts encoding members of the light-harvesting polypeptide family, such as LhcSR2, suggest restructuring of the photosynthetic apparatus during sulfur deprivation. There are also significant changes in levels of transcripts encoding enzymes involved in metabolic processes (e.g., carbon metabolism), intracellular proteolysis, and the amelioration of oxidative damage; a marked and sustained increase in mRNAs for a putative vanadium chloroperoxidase and a peroxiredoxin may help prolong survival of C. reinhardtii during sulfur deprivation. Furthermore, many of the sulfur stress-regulated transcripts (encoding polypeptides associated with sulfate uptake and assimilation, oxidative stress, and photosynthetic function) are not properly regulated in the sac1 mutant of C. reinhardtii, a strain that dies much more rapidly than parental cells during sulfur deprivation. Interestingly, sulfur stress elicits dramatic changes in levels of transcripts encoding putative chloroplast-localized chaperones in the sac1 mutant but not in the parental strain. These results suggest various strategies used by photosynthetic organisms during acclimation to nutrient-limited growth.Sulfur (S) is an essential element present in proteins, lipids, and various metabolites. It is critical for the association of metal ions to proteins (electron carriers and redox controllers) and is a component of metabolites that function in photoprotection (14, 29) and signal transduction (such as in symbiosis) (45). Because most organisms have limited S storage, their growth and development is dependent upon a continuous supply of this nutrient from the environment. The majority of accessible S in soil solutions is in the form of the SO 4 2Ϫ anion. However, in some cases the majority of soil SO 4 2Ϫ may not be readily available to the biota, since the SO 4 2Ϫ anion is often complexed with cations as insoluble salts that are tightly adsorbed onto the surface of soil particles or exists as a soluble anion that rapidly leaches through the soil matrix. Furthermore, a large proportion of soil SO 4 2Ϫ may be covalently bonded to organic molecules in the form of sulfate esters and sulfonates.The acquisition of SO 4 2Ϫ by plants and microorganisms is facilitated by specific transport systems. Following uptake, the anion is either used for the direct sulfation of compounds or...

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Insights into the Survival of Chlamydomonas reinhardtii during Sulfur Starvation Based on Microarray Analysis of Gene Expression

et al. 2004

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“…These responses can be divided into the P-specific responses and the general (or global) stress responses (Quisel et al, 1996;Davies and Grossman, 1998;Wykoff et al, 1998). P-specific responses facilitate mobilization and acquisition of Pi from both extracellular and intracellular sources (Quisel et al, 1996;Shimogawara et al, 1999), while the global responses allow for long-term survival by coordinating cellular metabolism and growth with nutrient availability.…”

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TheLPB1Gene Is Important for Acclimation ofChlamydomonas reinhardtiito Phosphorus and Sulfur Deprivation

et al. 2005

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Organisms exhibit a diverse set of responses when exposed to low-phosphate conditions. Some of these responses are specific for phosphorus limitation, including responses that enable cells to efficiently scavenge phosphate from internal and external stores via the production of high-affinity phosphate transporters and the synthesis of intracellular and extracellular phosphatases. Other responses are general and occur under a number of different environmental stresses, helping coordinate cellular metabolism and cell division with the growth potential of the cell. In this article, we describe the isolation and characterization of a mutant of Chlamydomonas reinhardtii, low-phosphate bleaching (lpb1), which dies more rapidly than wildtype cells during phosphorus limitation. The responses of this mutant to nitrogen limitation appear normal, although the strain is also somewhat more sensitive than wild-type cells to sulfur deprivation. Interestingly, depriving the cells of both nutrients simultaneously allows for sustained survival that is similar to that observed with wild-type cells. Furthermore, upon phosphorus deprivation, the lpb1 mutant, like wild-type cells, exhibits increased levels of mRNA encoding the PHOX alkaline phosphatase, the PTB2 phosphate transporter, and the regulatory element PSR1. The mutant strain is also able to synthesize the extracellular alkaline phosphatase activity upon phosphorus deprivation and the arylsulfatase upon sulfur deprivation, suggesting that the specific responses to phosphorus and sulfur deprivation are normal. The LPB1 gene was tagged by insertion of the ARG7 gene, which facilitated its isolation and characterization. This gene encodes a protein with strong similarity to expressed proteins in Arabidopsis (Arabidopsis thaliana) and predicted proteins in Oryza sativa and Parachlamydia. A domain in the protein contains some similarity to the superfamily of nucleotide-diphospho-sugar transferases, and it is likely to be localized to the chloroplast or mitochondrion based on programs that predict subcellular localization. While the precise catalytic role and physiological function of the putative protein is not known, it may function in some aspect of polysaccharide metabolism and/or influence phosphorus metabolism (either structural or regulatory) in a way that is critical for allowing the cells to acclimate to nutrient limitation conditions. The predominant form of available phosphorus (P) in the environment is inorganic phosphate (Pi), which is incorporated into numerous molecules including nucleic acids, phospholipids, and proteins. Pi availability is often limiting to plant growth, and while many soils have a Pi content of between 0.5 and 1.5 mM, the majority of the Pi is present as insoluble , and Ca 21 salts or as esterified organic compounds; these forms may not be readily assimilated. To maintain high crop yields, Pi is included as an abundant component of commercial fertilizers. Much of this supplementary Pi may be leached from agricultural fields and deposited into near...

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“…These responses can be divided into two categories, the P-specific responses and the general responses (4)(5)(6). The P-specific responses promote efficient mobilization and acquisition of P from extracellular and intracellular stores (e.g., synthesis and secretion of phosphatases with broad substrate specificity, accumulation of high affinity P i transporters) (5,7).…”

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Psr1, a nuclear localized protein that regulates phosphorus metabolism in Chlamydomonas

Wykoff

Grossman

Weeks

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the ways in which phosphorus metabolism is regulated in photosynthetic eukaryotes is critical for optimizing crop productivity and managing aquatic ecosystems in which phosphorus can be a major source of pollution. Here we describe a gene encoding a regulator of phosphorus metabolism, designated Psr1 (phosphorus starvation response), from a photosynthetic eukaryote. The Psr1 protein is critical for acclimation of the unicellular green alga Chlamydomonas reinhardtii to phosphorus starvation. The N-terminal half of Psr1 contains a region similar to myb DNA-binding domains and the C-terminal half possesses glutamine-rich sequences characteristic of transcriptional activators. The level of Psr1 increases at least 10-fold upon phosphate starvation, and immunocytochemical studies demonstrate that this protein is nuclear-localized under both nutrientreplete and phosphorus-starvation conditions. Finally, Psr1 and angiosperm proteins have domains that are similar, suggesting a possible role for Psr1 homologs in the control of phosphorus metabolism in vascular plants. With the identification of regulators such as Psr1 it may become possible to engineer photosynthetic organisms for more efficient utilization of phosphorus and to establish better practices for the management of agricultural lands and natural ecosystems. P hosphorus (P) is a major component of nucleic acids and phospholipids and is present in the biosphere as the oxidized anion, phosphate (P i ). P i is not easily accessible to most plants and microbes because it forms insoluble precipitates with common cations or is covalently bound to organic molecules (1-3). Crop yields are limited by P availability, and, consequently, P, in the form of P i , is an important component of commercial fertilizers. A considerable proportion of this ''supplementary'' P i is leached from agricultural fields and deposited into aquatic ecosystems, triggering rapid algal proliferation (algal blooms), which leads to eutrophication and fish kills (2). The sustainability of agricultural yields and quality of aquatic ecosystems would benefit from more efficient acquisition and utilization of P. Efficient P utilization by crop plants would decrease our dependence on rock P i reserves, the mining of which has serious economic and ecological consequences (3). Thus, a more complete understanding of P utilization in plants has significant implications with respect to both the environment and world agriculture.P limitation triggers a suite of ''starvation responses'' in most organisms. These responses can be divided into two categories, the P-specific responses and the general responses (4-6). The P-specific responses promote efficient mobilization and acquisition of P from extracellular and intracellular stores (e.g., synthesis and secretion of phosphatases with broad substrate specificity, accumulation of high affinity P i transporters) (5, 7). The general responses allow for long-term survival by coordinating the metabolism of the cell to nutrient availability and growth po...

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Responses to Deficiencies in Macronutrients

Cited by 24 publications

References 163 publications

Insights into the Survival of Chlamydomonas reinhardtii during Sulfur Starvation Based on Microarray Analysis of Gene Expression

Insights into the Survival of Chlamydomonas reinhardtii during Sulfur Starvation Based on Microarray Analysis of Gene Expression

TheLPB1Gene Is Important for Acclimation ofChlamydomonas reinhardtiito Phosphorus and Sulfur Deprivation

Psr1, a nuclear localized protein that regulates phosphorus metabolism in Chlamydomonas

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