Supplementation Of Ca2 Research Articles

The enhanced performance of Chlorococcum sphacosum in rich carbon wastewater treatment under the influence of calcium ion

The performance of microalgae-based wastewater treatment process is probably affected by high concentrations of organic carbon in wastewater, and calcium ions may influence this process. Nevertheless, the phenomena and mechanism involved have not been well explored. Here the performance of Chlorococcum sphacosum in treating wastewater with high concentrations of organic carbon was studied by coupling calcium ion concentration regulation (adding CaCl2 and free Ca2+ chelator EGTA) via physicochemical and transcriptomic analysis. It was found that photosynthesis and nutrients removal were suppressed and lipid accumulation was enhanced as the microalga was used to treat wastewater with high concentrations of organic carbon (more than 1500 mg/L). Simultaneously, antioxidant enzymes (SOD, CAT and POD) activity and calcium signaling-related protein (CaM, CDPK, and Ca2+-ATPase) content rose implying that the microalga was in a state of stress and calcium was involved in stress response. It was found that EGTA treatment further weakened the performance of microalgal photosynthesis and nutrients removal. However, the supplementation of Ca2+ had the opposite effect. Transcriptomic analysis revealed that Ca2+ strengthened the heterotrophic decomposition process of carbon (up-regulating the gene expression related to glycolysis and tricarboxylic acid cycle) and inhibited lipid accumulation (down-regulating lipid synthesis) via Ca2+ signalings transduction. Briefly, Ca2+ alleviated the stress of high concentration of organic carbon and strengthened the performance treating the corresponding wastewater.

Unraveling the significance of calcium as a biofilm promotion signal for Bacillus licheniformis strains isolated from dairy products

Bacillus licheniformis, a quick and strong biofilm former, is served as a persistent microbial contamination in the dairy industry. Its biofilm formation process is usually regulated by environmental factors including the divalent cation Ca2+. This work aims to investigate how different concentrations of Ca2+ change biofilm-related phenotypes (bacterial motility, biofilm-forming capacity, biofilm structures, and EPS production) of dairy B. licheniformis strains. The Ca2+ ions dependent regulation mechanism for B. licheniformis biofilm formation was further investigated by RNA-sequencing analysis. Results revealed that supplementation of Ca2+ increased B. licheniformis biofilm formation in a dose-dependent way, and enhanced average coverage and thickness of biofilms with complex structures were observed by confocal laser scanning microscopy. Bacterial mobility of B. licheniformis was increased by the supplementation of Ca2+ except the swarming ability at 20 mM of Ca2+. The addition of Ca2+ decreased the contents of polysaccharides but promoted proteins production in EPS, and the ratio of proteins/polysaccharides content was significantly enhanced with increasing Ca2+ concentrations. RNA-sequencing results clearly indicated the variation in regulating biofilm formation under different Ca2+ concentrations, as 939 (671 upregulated and 268 downregulated) and 951 genes (581 upregulated and 370 downregulated) in B. licheniformis BL2-11 were induced by 10 and 20 mM of Ca2+, respectively. Differential genes were annotated in various KEGG pathways, including flagellar assembly, two-component system, quorum sensing, ABC transporters, and related carbohydrate and amino acid metabolism pathways. Collectively, the results unravel the significance of Ca2+ as a biofilm-promoting signal for B. licheniformis in the dairy industry.

Calcium-mediated modulation of Pseudomonas fluorescens biofilm formation

Biofilm formation is usually affected by many environmental factors, including divalent cations. The purpose of the current work was to analyze how calcium (Ca2+) affects the biofilm formation of dairy Pseudomonas fluorescens isolates by investigating their growth, swarming motility, biofilm-forming capacity, extracellular polymeric substance production, and biofilm structures. Moreover, the regulation mechanism of Ca2+ involved in its biofilm formation was explored through RNA-sequencing analysis. This work revealed that supplementation of 5, 10, 15, and 20 mM Ca2+ significantly reduced the swarming motility of P. fluorescens strains (P.F2, P.F4, and P.F17), but the biofilm-forming ability and polysaccharide production were increased after the supplementation of 5 and 10 mM Ca2+. By the supplementation of Ca2+, complex structures with more cell clusters glued together in P. fluorescens P.F4 biofilms were confirmed by scanning electron microscopy, and increased biomass and coverage of P. fluorescens P.F4 biofilms were observed by confocal laser scanning microscopy. In addition, RNA-sequencing results showed that P. fluorescens P.F4 showed a transcriptional response to the supplementation of 10 mM Ca2+, and a total of 137 genes were significantly expressed. The differential genes were represented in 4 upregulated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways (nonribosomal peptide structures, quorum sensing, biosynthesis of siderophore group nonribosomal peptides, and phenylalanine metabolism), and 4 downregulated KEGG pathways (flagellar assembly, amino sugar and nucleotide sugar metabolism, nitrotoluene degradation, and cationic antimicrobial peptide resistance). The results indicate that Ca2+ might serve as an enhancer to substantially trigger the biofilm formation of dairy P. fluorescens isolates in the dairy industry.

Calcium nanoparticles (Ca-NPs) improve drought stress tolerance in Brassica napus by modulating the photosystem II, nutrient acquisition and antioxidant performance

Foliar-application of nano-particles enhanced the foliar nutrient status and crop growth and yield. It is hypothesized that being second messenger molecule, supplementation of Ca2+ via calcium nanoparticles (Ca-NPs) can trigger various signaling pathways of physiological processes which can lead to alleviate the adverse effects of drought stress on the growth of canola (Brassica napus L.). Nano-enabled foliar-application could be an ideal strategy for advancing agricultural productivity. The present study explored the role of calcium nanoparticles (Ca-NPs) in alleviating drought stress in hydroponic Brassica napus (B. napus) plants. The foliar applied Ca-NPs were spherically shaped with an average size of 86 nm. Foliar application of 100 mg L-1 Ca-NPs enhanced biomass of canola plants and considered as optimal dose. Ca-NPs at 100 mg L−1 has a greater favorable impact on mesophyll ultrastructure, PSI and PSII efficacy, gas exchange parameters, chlorophyll content, and mineral absorption. The Ca-NPs treatment increased NPQ and Y(NPQ) under drought condition, indicating a higher PSII protective response to stressed conditions with better heat dissipation as a photoprotective component of NPQ. Ca-NPs application also reduced oxidative stress damage as measured by a reduction in reactive oxygen species (ROS) generation in terms of hydrogen peroxide and malondialdehyde (H2O2 and MDA). Furthermore, Ca-NPs induced drought tolerance response corresponded to an increased in key antioxidative defense enzymes (SOD, POD, CAT, APX), as well as non-enzymatic components (protease, lipoxygenase, proline, total soluble protein contents, endogenous hormonal biosynthesis), and secondary metabolite expression in B. napus plants. Taken together, the results of this study offer new insights into the physiological and molecular mechanisms by which B. napus responds to Ca-NPs exposure.

Ca-mediated alleviation of Cd2+ induced toxicity and improved Cd2+ biomineralization by Sporosarcina pasteurii

Microbial induced carbonate precipitation has been widely used in the biomineralization of heavy metals Cd2+. However, the low Cd-tolerance of ureolytic bacteria limits the applications with only low Cd2+concentrations. In this study, we discovered a simple approach to significantly enhance the Cd2+ resistance of ureolytic bacteria through an immediate supplement of Ca2+. The Ca2+ protected the cells by reducing the extracellular and intracellular Cd2+ concentration by about 50%. As a result, the Cd2+ removal efficiency was notably improved by about 100% (52.72% to 99.43%, Cd = 5 mM) with Ca2+ supplement. Moreover, extremely high concentration of Cd2+ could be almost completely removed (99.46% at C0 = 20 mM and 99.60% at C0 = 50 mM) within 24 h. Microstructure analyses indicated that the mineralized precipitates were rhombohedral-shaped CdCO3, CaCO3, and (Ca0.67, Cd0.33)CO3. Furthermore, Ca2+ could also protect ureolytic bacteria against toxicity from other heavy metals.

Calcium Carbonate Addition Improves L-Methionine Biosynthesis by Metabolically Engineered Escherichia coli W3110-BL.

L-Methionine (L-Met) is a sulfur-containing amino acid, which is one of the eight essential amino acids to human body. In this work, the fermentative production of L-Met with genetically engineered Escherichia coli W3110-BL in a 5-L fermentor was enhanced through supplement of Ca2+ into the fermentation medium. With the addition of 30 g/L calcium carbonate (CaCO3), the titer of L-Met and yield against glucose reached 1.48 g/L and 0.09 mol/mol glucose, 57.45% higher than those of the control, respectively. The flux balance analysis (FBA) revealed that addition of CaCO3 strengthened the tricarboxylic acid cycle and increased the intracellular ATP concentration by 39.28%. The re-distribution of carbon, ATP, and cofactors flux may collaborate to improve L-Met biosynthesis with E. coli W3110-BL. The regulation of citrate synthase and oxidative phosphorylation pathway was proposed to be important for overproduction of L-Met. These foundations provide helpful reference in the following metabolic modification or fermentation control for further improvement of L-Met biosynthesis.

Antifungal Activity of Lactic Acid Bacteria Isolates and Their Associations: The Effects of Ca and Mg Divalent Cations.

The study of effects of Ca2+ and Mg2+ on antifungal activity of lactic acid bacteria (LAB) isolates and their associations revealed inducing and inhibiting effects on antifungal activity. The addition of Ca2+ essentially inhibited the antifungal effect of L. rhamnosus MDC9661 but stimulated the activity of RIN-2003-Ls, MDC9632 and MDC9633 strains, as well as their associations. Mg2+ partly increased the inhibitory activity of LAB isolates, while the addition of ions combination did not cause changes of their antifungal activity. The supplementation of Ca2+ stimulated the antifungal effect of most associations against Penicillium sp., Trichoderma viride, Geotrichum candidum, and Aspergillus flavus compared with the native conditions. The addition of Mg2+ induced the antifungal activity of RIN-2003-Ls, MDC9632, MDC9633, and INR-2010-Tsov-G-St combinations. The antifungal effects of most associations were increased in the presence of ions mixture. The natural LAB associations including VKPM B-3386, MDC9632, and MDC9633 could not suppress the growth of any tested mold; however, the supplementation of ions combination revealed their antifungal effect against all kinds of molds. The finding of substantial stimulation of the most LAB associations antifungal effect by metal ions can be basis for creation of new effective antifungal preparations by the supplementation of ions combined mixture.

Non-Conventional Metal Ion Cofactor Requirement of Dinoflagellate Alkaline Phosphatase and Translational Regulation by Phosphorus Limitation.

Alkaline phosphatase (AP) enables marine phytoplankton to utilize dissolved organic phosphorus (DOP) when dissolved inorganic phosphate (DIP) is depleted in the ocean. Dinoflagellate AP (Dino-AP) represents a newly classified atypical type of AP, PhoAaty. Despite While being a conventional AP, PhoAEC is known to recruit Zn2+ and Mg2+ in the active center, and the cofactors required by PhoAaty have been contended and remain unclear. In this study, we investigated the metal ion requirement of AP in five dinoflagellate species. After AP activity was eliminated by using EDTA to chelate metal ions, the enzymatic activity could be recovered by the supplementation of Ca2+, Mg2+ and Mn2+ in all cases but not by that of Zn2+. Furthermore, the same analysis conducted on the purified recombinant ACAAP (AP of Amphidinium carterae) verified that the enzyme could be activated by Ca2+, Mg2+, and Mn2+ but not Zn2+. We further developed an antiserum against ACAAP, and a western blot analysis using this antibody showed a remarkable up-regulation of ACAAP under a phosphate limitation, consistent with elevated AP activity. The unconventional metal cofactor requirement of Dino-AP may be an adaptation to trace metal limitations in the ocean, which warrants further research to understand the niche differentiation between dinoflagellates and other phytoplankton that use Zn–Mg AP in utilizing DOP.

Exposure to cadmium causes inhibition of otolith development and behavioral impairment in zebrafish larvae

Otolith consisting largely of calcium carbonate, fibrous and proteins, is vital for maintaining body balance and/or hearing of fish. The formation of otolith involves Ca2+ transport and deposition. In the present study, we investigated the effects of Cd2+ on otoliths development by using zebrafish embryos as model. The results showed that exposure to Cd2+ inhibited the utricular and saccular otoliths growth, indicated by reduced lateral areas. Swimming speeds were reduced and a losing balance control was observed in Cd2+ exposed larvae. The genes related to Ca2+ transport (e.g. plasma membrane Ca2+-ATPase isoform 2, pmca2; Ca2+-ATPase isoform 2, atp2b1a) and regulation (e.g. parathyroid hormone ligand type-1, pth1; stanniocalcin isoform 1, stc1) were significantly downregulated. However, the adverse effects of Cd2+ on otoliths growth and swimming activity can be protected by supplementation of Ca2+ in exposure medium. Body burden of Cd2+ in larvae was reduced upon the supplement with Ca2+. The overall results suggest that exposure to Cd2+ can inhibit influx of Ca2+, leading to less deposition of CaCO3 for otolith growth, and finally result in impaired balance control and swimming activity in zebrafish larvae.

Identification and Expression Analysis of an Atypical Alkaline Phosphatase in Emiliania huxleyi.

Emiliania huxleyi, a cosmopolitan coccolithophore in the modern ocean, plays an important role in the carbon cycle and local climate feedback as it can form extensive blooms, calcify, and produce dimethylsulfoniopropionate (DMSP) leading to the generation of dimethyl sulfide (DMS) which affects climate when oxidized in the atmosphere. It is known to be able to utilize dissolved organic phosphorus (DOP) by expressing a specific type of alkaline phosphatase (EHAP1) under phosphorus-limited conditions. In this study, we identified a new alkaline phosphatase (EH-PhoAaty) in this species, which we found belongs to the newly classified PhoAaty family. The expression of this atypical phosphatase was up-regulated under P-depleted conditions at both the transcriptional and translational levels, suggesting that E. huxleyi is able to express this AP to cope with phosphorus limitation. Comparative analysis revealed different transcriptional expression dynamics between eh-PhoAaty and ehap1, although both genes exhibited inducible expression under phosphate deficiency. In addition, after AP activity was eliminated by using EDTA to chelate metal ions, we found that AP activity was recovered with the supplement of Ca2+ and Zn2+, indicative of the adoption of Ca2+ as the cofactor under Zn-P co-limited conditions, likely a result of adaptation to oceanic environments where Zn2+ is often limiting.

The pathway of transmembrane cadmium influx via calcium-permeable channels and its spatial characteristics along rice root.

To develop elite crops with low cadmium (Cd), a fundamental understanding of the mechanism of Cd uptake by crop roots is necessary. Here, a new mechanism for Cd2+ entry into rice root cells was investigated. The results showed that Cd2+ influx in rice roots exhibited spatially and temporally dynamic patterns. There was a clear longitudinal variation in Cd uptake along rice roots, with the root tip showing much higher Cd2+ influx and concentration than the root mature zone, which might be due to the much higher expression of the well-known Cd transporter genes OsIRT1, OsNRAMP1, OsNRAMP5, and OsZIP1 in the root tip. Both the net Cd2+ influx and the uptake of Cd in rice roots were highly inhibited by ion channel blockers Gd3+ and TEA+, supplementation of Ca2+ and K+, and the plasma membrane H+-ATPase inhibitor vanadate, with Gd3+ and Ca2+ showing the most inhibitory effects. Furthermore, Ca2+- or Gd3+-induced reduction in Cd2+ influx and Cd uptake did not coincide with the expression of Cd transporter genes, but with that of two Ca channel genes, OsAAN4 and OsGLR3.4. These results indicate that Cd transporters are in part responsible for Cd2+ entry into rice root, and provide a new perspective that the Ca channels OsAAN4 and OsGLR3.4 might play an important role in rice root Cd uptake.

Ca2+ in Hybridization Solutions for Fluorescence in situ Hybridization Facilitates the Detection of Enterobacteriaceae.

Fluorescence in situ hybridization (FISH) has been employed to identify microorganisms at the single cell level under a microscope. Extensive efforts have been made to improve and extend the FISH technique; however, the development of a widely applicable protocol is a continuing challenge. The present study evaluated the effects of divalent cations in the hybridization solution on the FISH-based detection of various species of bacteria and archaea with rRNA-targeted probes. A flow cytometric analysis after FISH with a standard hybridization buffer detected positive signals from less than 30% of Escherichia coli IAM 1264 cells. However, the number of cells with positive signals increased to more than 90% after the addition of calcium chloride to the hybridization buffer. Mn2+ also had positive effects, whereas Mg2+ did not. The positive effects of Ca2+ were similarly observed for bacteria belonging to Enterobacteriaceae, including Enterobacter sakazakii IAM 12660T, E. aerogenes IAM 12348, Klebsiella planticola IAM 14202, and Salmonella enterica subsp. enterica serovar Typhimurium strain LT2. These results indicate that the supplementation of Ca2+ to the hybridization buffer for FISH contributes to the efficient detection of Enterobacteriaceae cells.

Molecular and biochemical analysis of supplementation of calcium under in vitro condition on tuberization in potato ( Solanum tuberosum L.)

Abstract Calcium plays an important role in plant physiology and various plant cell signaling pathways and alters several biochemical processes by activating specific enzymes. Cytosolic calcium (Ca2+) regulates the activity of Ca2+ dependent protein kinases, which phosphorylate various key metabolic enzymes. In this study, expression of the calcium (Ca2+) dependent proteins, calmodulin (CaM1) and Calcium dependent Protein Kinase (StCDPK), as well as the other important tuberizing pathway enzyme, the lipoxygenase (LOX; EC 1.13.11.12) were studied upon Ca2+ application to the single node segments of potato used for tuberization studies. Calcium at higher levels (9 mM) significantly improved the tuber number, growth and tuber yield under in vitro conditions. The expression level of the CaM1 and StCDPK were significantly higher in stolons and initial tubers showing positive correlation with supplemental Ca2+ and tuberization response. Similar trends were also observed with LOX enzyme activity, which increased by 18% and 25% with the supplementation of Ca2+ at 6 and 9 mM, respectively to the tuber induction medium, when compared to explants tuberizing on the medium without the Ca2+ control. Here we report the increase in tuberization, tuber growth and tuber yield with the supplementation of Ca2+ in tuberization induction medium could be attributed to the increased expression of the Ca2+ dependent proteins and enhanced lipoxygenase activity.

Calcium-mediated responses and glutamine synthetase expression in greater duckweed (Spirodela polyrhiza L.) under diethyl phthalate-induced stress

This study was carried out to assess the influence of diethyl phthalate (DEP) alone or associated with calcium chloride (CaCl2) on greater duckweed plants, emphasizing the implications of calcium in amelioration of DEP-induced stress on plant growth. Greater duckweed were treated with DEP in variable concentrations, as 0, 0.25, 0.5, 1.0 and 2.0mM for 7 days, or treated with the same concentration either 2mM DEP or 2mM DEP plus 10mM CaCl2·2H2O in different duration 0–7 days. Treatment with 2mM DEP resulted in increasing proline content, protease activity, and ammonia accumulation in duckweed tissues. NADH-glutamate dehydrogenase (NADH-GDH; EC 1.4.1.2) and Δ1-pyrroline-5-carboxylate reductase (P5CR; EC 1.5.1.2), two key enzymes in the glutamate pathway of proline synthesis, showed increase in activity with DEP treatment and positively correlated with proline accumulation. No further increase in proline accumulation was observed with addition of calcium chloride to the DEP-treated cultures. However, supplementation of Ca2+ can mitigate the adverse effect of DEP, at least in part to decrease the DEP-induced superoxide accumulation and increase in GDH activity for ammonia assimilation in duckweed fronds. In addition, effects of calcium on mitigation of DEP injury were also observed in glutamine synthetase (GS; EC 6.3.1.2) expression. Both GS1 and GS2 polypeptide accumulation and the level of total GS activity were nearly equivalent to the control. Exogenous proline protects GS2 from DEP-modulated redox damage in the chloroplast lysates but there is no remarkable protection effects on D1 (the 32kDa protein in photosystem II reaction center) degradation. In conclusion, the glutamate pathway of proline synthesis might be involved in mitigation of DEP-induced injury, and calcium plays an important role in increasing GDH, P5CR, and GS expression.

Ca2+ increases the specific coenzyme Q10 content in Agrobacterium tumefaciens

Of various metal ions (Ca2+, Cr3+, Cu2+, Fe2+, Mg2+, Mn2+, Ni2+ and Zn2+) added to the culture medium of Agrobacterium tumefaciens at 1 mM, only Ca2+ increased Coenzyme Q10 (CoQ(10)) content in cells without the inhibition of cell growth. In a pH-stat fed-batch culture, supplementation with 40 mM of CaCO3 increased the specific CoQ(10) content and oxidative stress by 22.4 and 48%, respectively. Also, the effect of Ca2+ on the increase of CoQ(10) content was successfully verified in a pilot-scale (300 L) fermentor. In this study, the increased oxidative stress in A. tumefaciens culture by the supplementation of Ca2+ is hypothesized to stimulate the increase of specific CoQ(10) content in order to protect the membrane against lipid peroxidation. Our results improve the understanding of Ca2+ effect on CoQ(10) biosynthesis in A. tumefaciens and should contribute to better industrial production of CoQ(10) by biological processes.

Identification and characterization of calcium and manganese transporting ATPase (PMR1) gene of Pichia pastoris

A gene homologous to Saccharomyces cerevisiae PMR1 has been cloned in the methylotrophic yeast Pichia pastoris. The entire P. pastoris PMR1 gene (PpPMR1) codes a protein of 924 amino acids. Sequence analysis of the PpPMR1 cDNA and the genomic DNA revealed that there is no intron in the coding region. The putative gene product contains all of the conserved regions observed in P-type ATPases and exhibits 66.2%, 60.3% and 50.6% identity to Pichia angusta (Hansenula polymorpha), Saccharomyces cerevisiae PMR1 and human ATP2C1 gene products, respectively. A pmr1 null mutant strain of P. pastoris exhibited growth defects in media with the addition of EGTA, but with supplementation of Ca2+ to a calcium-deficient media reversed the growth defects of the mutant strain. Manganese reversed the growth defects of the mutant strain; however, the cell growth was not as profound as the Ca2+ -supplemented media. The results demonstrated that the P. pastoris gene encodes the functional homologue of the S. cerevisiae PMR1 gene product, a P-type Ca2+/Mn2+ -ATPase. The DNA sequence of the P. pastoris PMR1 gene has been submitted to GenBank under Accession No. DQ239958.

The Effects of the NMR Shift-reagents Dy(PPP)2, Dy(TTHA) and Tm(DOTP) on Developed Pressure in Isolated Perfused Rat Hearts. The Role of Shift-reagent Calcium Complexes

The23Na NMR shift-reagent complexes (Dy(PPP)2, Dy(TTHA), and Tm(DOTP)) bind stoichiometric amounts of Ca2+. Thus, in perfused rat heart systems, a supplementation of Ca2+is required to maintain the requisite extracellular free calcium concentration ([Cao]f) and to approximate a physiological level of contractile function. The amount of reagent-bound Ca2+in a heart perfusate that contains a shift-reagent depends on: (1) Ca2+binding by excess ligand used during the preparation of the shift-reagent; and (2) the Ca2+binding affinity of the shift-reagent. To address point 1), we introduced a1H and31P NMR spectroscopic titration method to quantify directly the concentration of the excess ligand. We also used this method to minimize the amount of excess ligand (L) and thus the amount of Ca·L complex. To address point (2), we determined the stepwise Kd(μm) values of the Ca complexes of the three shift-reagents·: Dy(PPP)2, Kd1=0.09, Kd2=7.9; Dy(TTHA),Kd1 =10.66, Kd2=10.12; and Tm(DOTP), Kd1=0.502,Kd2 =4.98. The Kdvalues of the Ca complexes of the phosphonate and triphosphate based shift-reagents, Tm(DOTP) and Dy(PPP)2, respectively, are lower than those of the polyaminocarboxylate-based Dy(TTHA), indicating stronger Ca binding affinities for the former two types of complexes. We have also shown a positive correlation between [Cao]fand left ventricular developed pressure (LVDP) in perfused rat hearts. Dy(TTHA) has shown no effect on LVDP v[Cao]f. The LVDP values in the presence of the phosphonate and triphosphate based shift-reagents, however, were significantly higher than expected from the [Cao]flevels alone. Thus a positive inotropic effect, independent of [Cao]f, is evident in the presence of Tm(DOTP) or Dy(PPP)2.

Possible involvement of phosphoinositide-Ca2+ signaling in the regulation of alpha-amylase expression and germination of rice seed (Oryza sativa L.).

We have studied the effects of neomycin, a potent inhibitor of inositol phospholipid-specific phospholipase C (PLC), on the germination of rice seed and the gibberellin-induced expression of alpha-amylase in the aleurone layer and the scutellar tissues. It was shown that, in the absence of exogenous Ca2+, neomycin markedly reduced the germination speed and seedling growth of rice seeds and inhibited the gibberellin-induced expression of alpha-amylase in both secretory tissues. In addition, neomycin decreased the formation of inositol 1,4,5-trisphosphate (IP3) in the gibberellin-treated aleurone layer and the scutellar tissues. However, the inhibitory effects on the germination speed and the expression of alpha-amylase activity were overcome by supplementation of Ca2+. In addition, gibberellin elevated the level of IP3, and ABA prevented the gibberellin-induced formation of IP3, although ABA alone did not alter the IP3 level. The expression of a membrane-bound PLC molecule in rice aleurone layer was shown to be induced by gibberellin, and the gibberellin-induced expression of PLC was markedly delayed by treatment with ABA. These results strongly suggest that the phosphoinositide-Ca2+ signal transduction pathway may play an important role in the gibberellin-induced expression of alpha-amylase molecules closely related to the germination processes of rice seed.

Effects of calcium on lipid composition and function of plasma membrane and tonoplast vesicles isolated from roots of barley seedlings under salt stress

The effects of salt stress(200 mmol L‐1) and calcium (Ca) on the lipid composition and function of plasma membrane and tonoplast vesicles isolated from the roots of barley seedlings (Hordeum vulgare L. Jian 4) have been investigated. Nine days of exposure to 200 mmol L‐1 NaCl resulted in a significant increase in the electrolyte leakage and Na+/K+ ratio in the roots, sheaths, and leaves of barley. The index ofunsaturated fatty acids (IUFA) in plasma membrane (PM) and tonoplast (TP) vesicles, and the levels of galactolipid in TP increased (p<0.01). The contents of phospholipids in PM decreased (p<0.05). In contrast to salt treatment, supplement of Ca2+(17.5 mmol L‐1) obviously increased the phospholipids content, and significantly decreased the levels of galactolipids and IUFA in PM and TP vesicles. The results showed that the alleviating effect of Ca2+ on NaCl induced injury in barley seedlings may be related to the changes of membrane lipid composition including phospholipids, galactolipids, and their fatty acids.

Salinity effects on growth and on uptake and distribution of sodium and some essential mineral nutrients in sesame

Growth, uptake and allocation of sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and phosphate in plants of sesame (Sesamum indicum L. cv. Pb 1) exposed to 3 levels (10, 20, and 40 mM) of sodium chloride (NaCl) for a period of 3 weeks were investigated. A method of relative nutrient addition rate was adopted to simulate sparse nutrient supply from soils with low fertility. Parallel to the basal nutrient regime plants were subjected to nutrient regimes with high K+ or Ca2+. After one week of exposure to 40 mM NaCl the growth reduction of the plants was up to 33%. Plants treated with 10 or 20 mM NaCl contained relatively low Na+ concentrations and there were no consistent effects on growth. Presence of Na+ at all applied levels decreased the uptake of K+and Ca2+. Forty mM Na+ enhanced the uptake of phosphate. A high external K+ (1 mM) level did not improve growth and depressed the Ca2+ concentrations to critical levels especially in roots. Supplementation of Ca2+ (5 mM) neither reduced growth inhibition by Na+ nor diminished the internal Na+ concentration, but the level of K+ in the roots became lower. The sensitivity of sesame to Na+ salinity is linked to limited restriction of Na+ transport into the shoot, and interference of Na+ with K+, Ca2+ and phosphate uptake and distribution.