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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Iron ranks fourth in the sequence of abundance of the elements in the Earth's crust, but its low bio-availability often limits plant growth. When present in suboptimal amounts, the acquisition of iron by plants is aided by a suite of responses, comprising molecular and developmental changes that facilitate the uptake of iron from sparingly soluble pools. The expression of genes involved in the mobilization of iron (CsHA1), the reduction of ferric chelates (CsFRO1), and in the uptake of ferrous iron (CsIRT1) was investigated in epidermal cells of Fe-sufficient and Fe-deficient cucumber (Cucumis sativum L.) roots using the Laser Microdissection and Pressure Catapulting (LMPC) method. Growing plants hydroponically in media deprived of iron induced the differentiation of almost all epidermal cells into root hairs. No root hairs were formed under iron-replete conditions. The formation of root hairs in response to Fe starvation was associated with a dramatic increase in message levels of CsFRO1, CsIRT1, and the iron-inducible H(+)-ATPase isoform CsHA1, when compared to epidermal cells of Fe-sufficient plants. On the contrary, transcripts of a housekeeping ATPase isoform, CsHA2, were not detected in root hairs, suggesting that Fe-deficiency-induced acidification is predominantly mediated by CsHA1. These data show that the formation of root hairs in response to iron deficiency is associated with cell-specific accumulation of transcripts that are involved in iron acquisition. The results also show that this includes the differential regulation of ATPase isoforms with similar function, but supposedly different characteristics, to counteract the imbalance in nutrient supply efficiently.
J Exp Bot 2008
PMID:Laser microdissection-assisted analysis of the functional fate of iron deficiency-induced root hairs in cucumber. 1831 19

This review examines the hypotheses that developmental programmed cell death in leaves is mediated (i) by sugar starvation in the leaf cells or (ii) by sugar accumulation in these cells. Experimental evidence for both hypotheses is critically discussed and found to be lacking. For example, some papers show that sugars prevent senescence of cut leaves placed in darkness, and prevent low sugar levels in the leaves. In these tests, the sugars seem to replace photosynthesis, hence the results have little relevance to leaf senescence in intact plants in the light. Low nitrogen nutrition and high light results in earlier senescence than the low nitrogen treatment alone. This is accompanied by high sugar levels in the leaves. The results have led to the idea that accumulation of sugars is the cause of the additional effect, or more generally, that sugar accumulation is always the direct cause of leaf senescence. Results from over-expressing, or knocking out, hexokinase genes tend to support the high sugar hypothesis, but pleiotropic effects confound this conclusion. In addition, several experiments show the effects of treatments on senescence without the increase in leaf sugar levels. Nonetheless, sugar levels are usually measured in whole leaves. Such an overall level does not reflect the differences in the onset of senescence between tissues and cells, and can therefore not be used as an argument for or against either of the two hypotheses. It is argued that future work should determine the time line of the concentrations of various sugars in various cells and cellular compartments, in relation to senescence processes in the same cells. Taken together, the data are not decisive. It is possible that neither of the two hypotheses is correct.
J Exp Bot 2008
PMID:Is the onset of senescence in leaf cells of intact plants due to low or high sugar levels? 1845 32

Cluster root (CR) formation contributes much to the adaptation to phosphorus (P) deficiency. CR formation by white lupin (Lupinus albus L.) is affected by the P-limiting level in shoots, but not in roots. Thus, shoot-derived signals have been expected to transmit the message of P-deficiency to stimulate CR formation. In this study, it is shown that sugars are required for a response to P starvation including CR formation and the expression of P starvation-induced genes. White lupin plants were grown in vitro on P-sufficient or P-deficient media supplemented with sucrose for 4 weeks. Sucrose supply stimulated CR formation in plants on both P-sufficient and P-deficient media, but no CR appeared on the P-sufficient medium without sucrose. Glucose and fructose also stimulated CR formation on the P-sufficient medium. On the medium with sucrose, a high concentration of inorganic phosphate in leaves did not suppress CR formation. Because sorbitol or organic acid in the media did not stimulate CR formation, the sucrose effect was not due to increased osmotic pressure or enriched energy source, that is, sucrose acted as a signal. Gene transcription induced by P starvation, LaPT1 and LaPEPC3, was magnified by the combination of P limitation and sucrose feeding, and that of LaSAP was stimulated by sucrose supply independently of P supply. These results suggest that at least two sugar-signalling mediating systems control P starvation responses in white lupin roots. One system regulates CR formation and LaSAP expression, which acts even when P is sufficient if roots receive sugar as a signal. The other system controls LaPT1 and LaPEPC3 expression, which acts when P is insufficient.
J Exp Bot 2008
PMID:Sugar signalling mediates cluster root formation and phosphorus starvation-induced gene expression in white lupin. 1848 37

Maize (Zea mays) is the most widely cultivated crop around the world; however, it is commonly affected by phosphate (Pi) deficiency in many regions, particularly in acid and alkaline soils of developing countries. To cope with Pi deficiency, plants have evolved a large number of developmental and biochemical adaptations; however, for maize, the underlying molecular basis of these responses is still unknown. In this work, the transcriptional response of maize roots to Pi starvation at 1, 3, 6, and 10 d after the onset of Pi deprivation was assessed. The investigation revealed a total of 1179 Pi-responsive genes, of which 820 and 363 genes were found to be either up- or down-regulated, respectively, by 2-fold or more. Pi-responsive genes were found to be involved in various metabolic, signal transduction, and developmental gene networks. A large set of transcription factors, which may be potential targets for crop breeding, was identified. In addition, gene expression profiles and changes in specific metabolites were also correlated. The results show that several dicotyledonous plant responses to Pi starvation are conserved in maize, but that some genetic responses appear to be more specific and that Pi deficiency leads to a shift in the recycling of internal Pi in maize roots. Ultimately, this work provides a more comprehensive view of Pi-responses in a model for economically important cereals and also sets a framework to produce Pi-specific maize microarrays to study the changes in global gene expression between Pi-efficient and Pi-inefficient maize genotypes.
J Exp Bot 2008
PMID:Transcript profiling of Zea mays roots reveals gene responses to phosphate deficiency at the plant- and species-specific levels. 1850 42

A systems approach has previously been used to follow the response behaviour of Arabidopsis thaliana plants upon sulphur limitation. A response network was reconstructed from a time series of transcript and metabolite profiles, integrating complex metabolic and transcript data in order to investigate a potential causal relationship. The resulting scale-free network allowed potential transcriptional regulators of sulphur metabolism to be identified. Here, three sulphur-starvation responsive transcription factors, IAA13, IAA28, and ARF-2 (ARF1-Binding Protein), all of which are related to auxin signalling, were selected for further investigation. IAA28 overexpressing and knock-down lines showed no major morphological changes, whereas IAA13- and ARF1-BP-overexpressing plants grew more slowly than the wild type. Steady-state metabolite levels and expression of pathway-relevant genes were monitored under normal and sulphate-depleted conditions. For all lines, changes in transcript and metabolite levels were observed, yet none of these changes could exclusively be linked to sulphur stress. Instead, up- or down-regulation of the transcription factors caused metabolic changes which in turn affected sulphur metabolism. Auxin-relevant transcription factors are thus part of a complex response pattern to nutrient starvation that serve as coordinators of the metabolic shifts driving sulphur homeostasis rather then as direct effectors of the sulphate assimilation pathway. This study provides the first evidence ever presented that correlates auxin-related transcriptional regulators with primary plant metabolism.
J Exp Bot 2008
PMID:Transcription factors relevant to auxin signalling coordinate broad-spectrum metabolic shifts including sulphur metabolism. 1859 13

The effect of two different copper conditions (deficiency and excess) on the amino acid composition in B. carinata xylem sap was analysed. When the Cu in the nutrient solution was increased from 0.12 to 2.5 or 5 microM, the concentrations of histidine, threonine, glutamine, proline, methionine, and glycine were much increased in the xylem sap. When Cu was made deficient in the nutrient solution by decreasing its concentration from 0.12 microM to 0 microM, nicotianamine, glutamine, and threonine were significantly increased in the xylem sap. Aqueous solutions containing different Cu-amino acid complexes (simulated saps) responded in a specific way to the changes in pH, providing a signature that was used to evaluate, by comparison with the real xylem sap, the importance of each amino acid in the xylem transport of Cu. For a single amino acid, the free solution Cu(2+) concentration versus pH titration curves for histidine and proline were the most similar to that for xylem under Cu excess. Under Cu deficiency, this Cu concentration versus pH titration curve appeared to be very similar to that for nicotianamine. It is concluded that increased Cu concentrations induced the selective synthesis of certain amino acids in the sap, of which histidine and proline are the most important. Under Cu deficiency, the concentration of nicotianamine was induced the most. The fact that nicotianamine is induced under Cu starvation and not under Cu excess, is in contrast to similar studies indicating species-specific reactions. However, the induction of nicotianamine under Cu starvation is in line with recent molecular data of the role of nicotianamine in intracellular Cu delivery.
J Exp Bot 2009
PMID:Nicotianamine and histidine/proline are, respectively, the most important copper chelators in xylem sap of Brassica carinata under conditions of copper deficiency and excess. 1903 52

The plasma membrane (PM) proton pump ATPases (H(+)-ATPases) are involved in almost all aspects of biology. They are plant specific and several members of this family are supposed to play a key role in nutrient acquisition. At present, only some members of this gene family in plants have been characterized. However, no nutrient uptake associated H(+)-ATPase gene in rice has been functionally analysed. It is reported here that OsA8, a typical PM H(+)-ATPases gene that was predominantly expressed in roots of rice, is down-regulated by nutrient deficiency. The Osa8 mutant had a relatively smaller size and root to shoot biomass ratio, but higher ATPase activity than its wild-type counterparts under phosphorus (P) starvation conditions. Knockout of OsA8 affected the expression of several OsA genes and the high affinity phosphate transporter, OsPT6, and resulted in a higher P concentration in the roots and a lower amount of P in the shoots. These analyses demonstrate that OsA8 not only influences the uptake of P by roots, but also the translocation of P from the roots to the shoots in rice.
J Exp Bot 2009
PMID:Proton pump OsA8 is linked to phosphorus uptake and translocation in rice. 1904 99

Nicotianamine (NA) is a non-protein amino acid derivative synthesized from S-adenosyl L-methionine able to bind several metal ions such as iron, copper, manganese, zinc, or nickel. In plants, NA appears to be involved in iron availability and is essential for the plant to complete its biological cycle. In graminaceous plants, NA is also the precursor in the biosynthesis of phytosiderophores. Arabidopsis lines accumulating 4- and 100-fold more NA than wild-type plants were used in order to evaluate the impact of such an NA overaccumulation on iron homeostasis. The expression of iron-regulated genes including the IRT1/FRO2 iron uptake system is highly induced at the transcript level under both iron-sufficient and iron-deficient conditions. Nevertheless, NA overaccumulation does not interfere with the iron uptake mechanisms since the iron levels are similar in the NA-overaccumulating line and wild-type plants in both roots and leaves under both sufficient and deficient conditions. This observation also suggests that the translocation of iron from the root to the shoot is not affected in the NA-overaccumulating line. However, NA overaccumulation triggers an enhanced sensitivity to iron starvation, associated with a decrease in iron availability. This study draws attention to a particular phenotype where NA in excess paradoxically leads to iron deficiency, probably because of an increase of the NA apoplastic pool sequestering iron. This finding strengthens the notion that extracellular NA in the apoplast could be a major checkpoint to control plant iron homeostasis.
J Exp Bot 2009
PMID:Increased sensitivity to iron deficiency in Arabidopsis thaliana overaccumulating nicotianamine. 1918 76

Molecular chaperones of the heat shock cognate 70 kDa (HSC70) family are highly conserved in all living organisms and assist nascent protein folding in normal physiological conditions as well as in biotic and abiotic stress conditions. In the absence of specific inhibitors or viable knockout mutants, cytosolic/nuclear HSC70-1 overexpression (OE) and mutants in the HSC70 co-chaperone SGT1 (suppressor of G(2)/M allele of skp1) were used as genetic tools to identify HSC70/SGT1 functions in Arabidopsis development and abiotic stress responses. HSC70-1 OE caused a reduction in root and shoot meristem activities, thus explaining the dwarfism of those plants. In addition, HSC70-1 OE did not impair auxin-dependent phenotypes, suggesting that SGT1 functions previously identified in auxin signalling are HSC70 independent. While responses to abiotic stimuli such as UV-C exposure, phosphate starvation, or seedling de-etiolation were not perturbed by HSC70-1 OE, it specifically conferred gamma-ray hypersensitivity and tolerance to salt, cadmium (Cd), and arsenic (As). Cd and As perception was not perturbed, but plants overexpressing HSC70-1 accumulated less Cd, thus providing a possible molecular explanation for their tolerance phenotype. In summary, genetic evidence is provided for HSC70-1 involvement in a limited set of physiological processes, illustrating the essential and yet specific functions of this chaperone in development and abiotic stress responses in Arabidopsis.
J Exp Bot 2009
PMID:Altered expression of cytosolic/nuclear HSC70-1 molecular chaperone affects development and abiotic stress tolerance in Arabidopsis thaliana. 1944 14

Knowledge of the molecular basis of plant resistance to pathogens in species other than Arabidopsis is limited. The function of Fa WRKY1, the first WRKY gene isolated from strawberry (Fragaria x ananassa), an important agronomical fruit crop, has been investigated here. Fa WRKY1 encodes a IIc WRKY transcription factor and is up-regulated in strawberry following Colletotrichum acutatum infection, treatments with elicitors, and wounding. Its Arabidopsis sequence homologue, At WRKY75, has been described as playing a role in regulating phosphate starvation responses. However, using T-DNA insertion mutants, a role for the At WRKY75 and Fa WRKY1 in the activation of basal and R-mediated resistance in Arabidopsis is demonstrated. At wrky75 mutants are more susceptible to virulent and avirulent isolates of Pseudomonas syringae. Overexpression of Fa WRKY1 in At wrky75 mutant and wild type reverts the enhanced susceptible phenotype of the mutant, and even increases resistance to avirulent strains of P. syringae. The resistance phenotype is uncoupled to PATHOGENESIS-RELATED (PR) gene expression, but it is associated with a strong oxidative burst and glutathione-S-transferase (GST) induction. Taken together, these results indicate that At WRKY75 and Fa WRKY1 act as positive regulators of defence during compatible and incompatible interactions in Arabidopsis and, very likely, Fa WRKY1 is an important element mediating defence responses to C. acutatum in strawberry. Moreover, these results provide evidence that Arabidopsis can be a useful model for functional studies in Rosacea species like strawberry.
J Exp Bot 2009
PMID:Evidence for a positive regulatory role of strawberry (Fragaria x ananassa) Fa WRKY1 and Arabidopsis At WRKY75 proteins in resistance. 1947 Jun 57


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