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Phosphate Availability (phosphate + availability)
Selected AbstractsPhosphate availability from phosphate rock as related to nitrogen form and the nitrification inhibitor DMPPJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2006Rahmatullah [source] Phosphate availability regulates biosynthesis of two antibiotics, prodigiosin and carbapenem, in Serratia via both quorum-sensing-dependent and -independent pathwaysMOLECULAR MICROBIOLOGY, Issue 2 2003Holly Slater Summary Serratia sp. ATCC 39006 produces two secondary metabolite antibiotics, 1-carbapen-2-em-3-carboxylic acid (Car) and the red pigment, prodigiosin (Pig). We have previously reported that production of Pig and Car is controlled by N -acyl homoserine lactone (N -AHL) quorum sensing, with synthesis of N -AHLs directed by the LuxI homologue SmaI, and is also regulated by Rap, a member of the SlyA family. We now describe further characterization of the SmaI quorum-sensing system and its connection with other regulatory mechanisms. We show that the genes responsible for biosynthesis of Pig, pigA,O, are transcribed as a single polycistronic message in an N -AHL-dependent manner. The smaR gene, transcribed convergently with smaI and predicted to encode the LuxR homologue partner of SmaI, was shown to possess a negative regulatory function, which is uncommon among the LuxR-type transcriptional regulators. SmaR represses transcription of both the pig and car gene clusters in the absence of N -AHLs. Specifically, we show that SmaIR exerts its effect on car gene expression via transcriptional control of carR, encoding a pheromone-independent LuxR homologue. Transcriptional activation of the pig and car gene clusters also requires a functional Rap protein, but Rap dependency can be bypassed by secondary mutations. Transduction of these suppressor mutations into wild-type backgrounds confers a hyper-Pig phenotype. Multiple mutations cluster in a region upstream of the pigA gene, suggesting this region may represent a repressor target site. Two mutations mapped to genes encoding pstS and pstA homologues, which are parts of a high-affinity phosphate transport system (Pst) in Escherichia coli. Disruption of pstS mimicked phosphate limitation and caused concomitant hyper-production of Pig and Car, which was mediated, in part, through increased transcription of the smaI gene. The Pst and SmaIR systems define distinct, yet overlapping, regulatory circuits which form part of a complex regulatory network controlling the production of secondary metabolites in Serratia ATCC 39006. [source] PRODUCTION OF PARALYTIC SHELLFISH TOXINS BY APHANIZOMENON SP.JOURNAL OF PHYCOLOGY, Issue 4 2002LMECYA 31 (CYANOBACTERIA) We examined intracellular and extracellular paralytic shellfish toxins (PST) in a strain of Aphanizomenon sp. (LMECYA31) isolated from a Portuguese freshwater reservoir throughout the growth cycle and under different conditions affected by temperature and nitrate and phosphate availability. PST concentrations and compositions were greatly influenced by cell density, growth stage, and temperature and nutrients conditions. On a per-cell basis results showed (1) the enhancement of PST cell quota after the end of exponential growth phase in nutrient replete batch cultures, (2) the absence of a PST increment at late growth stages under phosphate limitation, (3) a rise in PST maximum cell quota under nitrate depletion, and (4) the enhancement of toxin production at higher temperatures. The relative proportion of the four toxins detected, neoSTX, dcSTX, STX and GTX5, also changed within and between culture settings. While growing under phosphate rich media cells produced mainly GTX5 and neoSTX, whereas under phosphate limitation the proportion of STX and dcSTX increased substantially with culture age. Large amounts of extracellular toxins were found in the culture medium, increasing during culture time. Extracellular toxin composition in each culture was fairly constant and always similar to the intracellular composition found at late stages of growth. This further supported other research that indicates that PSTs are released to the water through cell lysis, and a significant concentration of PST may be expected to remain in the water upon the collapse of a toxic bloom or after cells removal by water treatment. [source] Characterization of a type A response regulator in the common bean (Phaseolus vulgaris) in response to phosphate starvationPHYSIOLOGIA PLANTARUM, Issue 3 2008Yolanda Camacho Type A response regulators are a family of genes in Arabidopsis thaliana involved primarily in cytokinin signal transduction. A member of this family was isolated from a cDNA library constructed from bean plants (Phaseolus vulgaris) grown under conditions of phosphate starvation. The complete cDNA sequence showed the presence of the DDK domain, which is the hallmark of the response regulator family. Expression of the P. vulgaris response regulator 1 (PvRR1) showed clear regulation based on phosphate availability because transcript levels increased during phosphate starvation and returned to basal levels after resupplementation with phosphorus. Nitrogen and potassium starvation also upregulated PvRR1, indicating that cross talk with other nutrient signaling pathways might occur. Addition of cytokinins to plants growing under phosphate-sufficient conditions stimulated PvRR1 transcript levels both in detached leaves and in roots. However, cytokinins strongly inhibited PvRR1 expression in phosphate-starved plants after 24 h of incubation. At the protein level, subcellular localization of PvRR1 indicated that it is a nuclear protein and that phosphate starvation modified protein levels but not the localization. [source] Mtha1, a Plasma Membrane H+ -ATPase Gene from Medicago truncatula, Shows Arbuscule-Specific Induced Expression in Mycorrhizal TissuePLANT BIOLOGY, Issue 6 2002F. Krajinski Abstract: Transport processes between plant and fungal cells are key elements in arbuscular mycorrhiza (AM), where H+ -ATPases are considered to be involved in active uptake of nutrients from the symbiotic interface. Genes encoding H+ -ATPases were identified in the genome of Medicago truncatula and three cDNA fragments of the H+ -ATPase gene family (Mtha1 - 3) were obtained by RT-PCR using RNA from M. truncatula mycorrhizal roots as template. While Mtha2 and Mtha3 appeared to be constitutively expressed in roots and unaffected by AM development, transcripts of Mtha1 could only be detected in AM tissues and not in controls. Further analyses by RT-PCR revealed that Mtha1 transcripts are not detectable in shoots and phosphate availability did not affect RNA accumulation of the gene. Localization of transcripts by in situ hybridization on AM tissues showed that Mtha1 RNA accumulates only in cells containing fungal arbuscules. This is the first report of arbuscule-specific induced expression of a plant H+ -ATPase gene in mycorrhizal tissues. [source] Phosphate Induces Rapid H2O2 Generation in Soybean Suspension CellsPLANT BIOLOGY, Issue 2 2000T. Shigaki Abstract: Involvement of reactive oxygen species has been implicated in plant defence against pathogens. We report here a novel pathway of H2O2 generation induced by the addition of phosphate in soybean (Glycine max L.) cell suspension cultures. This H2O2 generation was initiated shortly after the addition of phosphate, and lasted only approximately one hour, as opposed to several hours observed during an attack by an avirulent strain of the bacterial pathogen Pseudomonas syringae pv. glycinea (Psg). In addition, when cell cultures were treated with both phosphate and the avirulent pathogen, two distinct oxidative burst events were observed. In contrast to DPI-sensitive Psg -induced H2O2 generation, phosphate-induced H2O2 generation was insensitive to this NADPH oxidase inhibitor. This suggests that an NADPH oxidase-independent pathway may be involved in the phosphate-induced H2O2 accumulation, which could be involved in sensing of phosphate availability in the environment. [source] The decline of metallophyte vegetation in floodplain grasslands: Implications for conservation and restorationAPPLIED VEGETATION SCIENCE, Issue 1 2009Esther C.H.E.T. Lucassen Abstract Question: Which biogeochemical processes are responsible for the decline of endemic metallophyte vegetation in floodplain grasslands? Location: Floodplain grasslands along the River Geul (the Netherlands) and metalliferous mine spoils near the River Geul (Belgium). Methods: In order to find factors and soil processes that have caused a decline of metallophytes and an increase of pseudo-metallophytes in floodplain grasslands, a soil study was done at locations currently and formerly dominated by metallophytes. In addition, changes in soil chemistry in recent decades in floodplain grasslands were investigated. Finally, a 2-year plant growth experiment was performed in the field, to test the effects of improving soil conditions by topsoil removal. Results: Metallophytes only occur on acidic floodplain soils (pH-H2O 5.0-5.5) with relatively high Zn availability (total Zn >40 ,mol g,1; Zn/Ca>0.8; Zn-H2O>59 ,mol kg,1) combined with low phosphate availability (Olsen-P,1250 ,mol kg,1). The Olsen-P and total Ca concentrations were relatively high in topsoil (0-20 cm), while total Zn was high throughout the soil profile (0-50 cm). Removal of topsoil led to recovery of P and Zn availability. Under the new soil conditions there was almost no growth and expansion of pseudo-metalliferous grasses in time, wheras metallophytes easily established, maintained and reproduced with significant increases in cover over time. Conclusions: On a global scale, metallophyte vegetation types are increasingly under threat of extinction. Our study shows that factors leading to higher soil alkalinity inhibit Zn availability at the expense of the metallophyte vegetation. Factors leading to a higher Olsen-P concentration stimulate the growth of more competitive pseudo-metallophyte grasses. Both eutrophication and alkalinisation have contributed to the decline of metallophyte vegetation in floodplains of the River Geul. Removal of the alkaline- and phosphate-enriched soil top layer restores the original soil chemistry and enables re-colonisation by the metallophyte vegetation. The results can be applied in conservation and restoration strategies for such sites. [source] | |||||||||||||