vahideh Shaabani Zenoozagh; Nasser Aliasgharzad; Jaffar Majidi; Roghaieh Hajiboland; Behzad Baradaran; Leili Aghebati-Maleki
Abstract
Introduction: Glomalin is a specific glycoprotein produced by the fungi belonging to phylum Glomeromycota and plays a key role in soil carbon and nitrogen storage. This also has a significant role in the stable aggregates formation and establishment of microbial communities in soil. Assimilated plant ...
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Introduction: Glomalin is a specific glycoprotein produced by the fungi belonging to phylum Glomeromycota and plays a key role in soil carbon and nitrogen storage. This also has a significant role in the stable aggregates formation and establishment of microbial communities in soil. Assimilated plant C which is allocated to the mycorrhizal fungus, appears as a recalcitrant glycoprotein (glomalin) in cell walls of hyphae and spores. Considering global warming due to increasing greenhouse gases, this phenomenon cab be important in carbon sequestration and reducing CO2 in atmosphere. Chemical fertilizers can affect symbiotic relations of these fungi, which in turn affect glomalin production.
Materials and Methods: In a factorial completely randomized design with three replication, clover plants (Trifolium repense L.) were included with Rhizophagus irregularis and/or Rhizobium leguminosarum bv. Trifolii. Four levels of nitrogen (0, 2, 6 and 10 mM as nitrate) in Newman & Romheld nutrient solution were applied to the pots containing 1.5 kg sterile sand. The pots were daily irrigated with nutrient solution containing the above-mentioned levels of nitrogen. Clover plants were excised after 12 weeks of growth. Fine roots were cleaned with %10 KOH and then stained using lactoglycerol trypan blue. Root colonization percentage was determined by grid line intersections method (GLM) described by Norrif et al (1992). For glomalin extraction, hyphal or root samples were autoclaved at 121 ⁰C with 50 mM sodium citrate buffer for 60 min in three cycles. Sand glomalin (SG) and root glomalin (RG) were measured by Bradford method after extraction. Nitrogen concentration in shoot and root was measured according to the standard method.
Results and Discussion: By increasing nitrogen level, the SG significantly decreased (p < 0.01), and at 2 mM, a 63.5 % decrease in SG was observed with relative to the nitrogen-free control. In the rhizobial treated pots, SG production increased by fungal inoculation (p < 0.01). The interaction between bacteria and AM was also significant in production of SG. At the presence of rhizobium bacteria, glomalin production by AM fungi increased significantly. The changes of glomalin content were not impacted by the presence of bacteria in the uninoculated pots with fungi. The highest amount of SG was recorded in the co-inoculated plants with nitrogen-free level. The amount of RG enhanced by increasing nitrogen concentration in nutrient solution. At 10 mM, RG increased by 12.90 %, 11.91 % and 1.44 % compared to the levels of 0, 2 and 6 mM, respectively. As the nitrogen level increased, the percentage of root colonization increased with respect to the control. Nitrogen concentration in shoot and root was enhanced by N increment to 10mM.
Conclusion: Carbon sequestration via glomali synthase by AM fungi is an important pathway for capturing CO2 from atmosphere. Field management measures help AM development of glomalin production. Based on our results, co-inoculated plants with AM and rhizobuim seem to positively affect the production of this glycoprotein. On the other hand, SG decreased significantly by increasing nitrogen concentrations in the nutrient solution. RG, however, increased significantly as a result of increased nitrogen in both fungal inoculations. The highest amount of RG was recorded in the co-inoculated plants with 10mM level. Glomalin synthesis by the fungi is positively affected by the soil nitrogen availability. Nitrogen is the main constituent of this glycoprotein. Plant photosynthates are translocated to the fungal organs via roots and mainly utilized for glomalin synthesis in hyphal and spore cell walls. During this process, nitrogen plays an important role as a constituent of the glycoprotein. The Bradford method was used for glomalin determination in this study. The method is not specific for glomalin and can also measure other glomalin related proteins and glycoproteins. Other proteins increased by N fertilization can hence be measured based on Bradford method. Once plant assimilates are translocated to the fungi, they may be transformed to the nitrogenous compounds if sufficient nitrogen sources are available. Accordingly, a considerable amount of fixed carbon is assimilated in fungal organs and soil particles. It can be concluded that carbon sequestration by arbuscular mycorrhizal symbiosis in terrestrial ecosystems can be improved by N fertilization at optimum level. In addition, the presence of rhizobium bacteria can meet the nitrogen requirement of plants through biological stabilization of nitrogen.
Elham Malekzadeh; Jafar Majidi; Nasser Aliasgharzad; Jalal Abdolalizadeh
Abstract
Introduction: Glomalin is known as a specific fungal glycoprotein belonging to the order Glomerales in phylum Glomeromycota and has been introduced as a heat shock protein. We hypothesised that increasing the level of Pb would lead to increase in glomalin production. Glomalin is usually determined by ...
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Introduction: Glomalin is known as a specific fungal glycoprotein belonging to the order Glomerales in phylum Glomeromycota and has been introduced as a heat shock protein. We hypothesised that increasing the level of Pb would lead to increase in glomalin production. Glomalin is usually determined by two methods, the Bradford protein dye-binding assay and the enzyme-linked immunosorbent assay (ELISA). Since many laboratories are not equipped to carry out the ELISA assay, many studies have measured glomalin-related soil protein using the Bradford colorimetric total protein assay. While, the ELISA method specifically measures glomalin by using monoclonal antibody MAb32B11.
Materials and Methods: The pot experiment was conducted in the sterile free-glomalin sand with Trifolium repens L. mycorrhized by Rhizophagus irregularis fungus and treated with the Pb levels of 0, 150, 300 and 450 µM. Thus, in vitro experiment was performed in two-compartments plates containing of the transformed carrot roots (Daucus carota L.) mycorrhized with the same fungus in root compartment and hyphal compartment treated with the Pb levels of 0, 0.01, 0.1 and 1 mM as Pb(NO3)2. For glomalin extraction, hyphal or root samples were autoclaved at 121 ⁰C with 50 mM sodium citrate buffer for 60 min in three cycles. Protein concentrations in the extracted samples were determined using a modified Bradford protein assay. Also, glomalin content in the samples were determined by indirect ELISA using monoclonal antibody MAb32B11. The percentages of the total root length were colonised by mycorrhizal fungi in pot culture and both hyphal and spore densities in the metal-containing hyphal compartment were determined.
Results and Discussion: In the in vitro culture the percentage of total hyphae and spore frequency decreased, while Bradford reactive total hyphal protein (BRHP) and Immunoreactive hyphal protein (IRHP) in hyphal compartment increased as the concentrations of Pb increased. Also, there was positive and significant correlation between immunoreactive hyphal protein (IRHP) and Bradford reactive total hyphal protein (BRHP) in hyphal compartment of in vitro culture (r= 0.941**). In the pot culture, the percentage of the total mycorrhized root length in all the treatments increased compared to the unleaded control as the concentrations of Pb raised. In general, Bradford reactive total protein and Immunoreactive protein in both the hyphal and root compartments of pot culture increased with increasing the Pb levels. Also, there were positive and significant correlations between immunoreactive hyphal protein (IRHP) with Bradford reactive total hyphal protein (BRHP) (r= 0.845 **) and immunoreactive root protein (IRRP) with Bradford reactive total root protein (BRRP) (r= 0.706 **) in pot experiment. Some previously researches had reported correlation between ELISA with Bradford contents, whether, Bradford and ELISA values were nearly the same, this means that the extraction process mostly separates glomalin. The results of non-mycorrhizal roots indicated that a small proportion of root protein is cross-reactive with the MAb32B11 antibody. There are some evidences that MAb32B11 is slightly cross-reactive with plant compounds, non-AMF species, and non-target proteins present in large concentration, such as BSA. Additionally, we found the increasing of BRRP contents of AMF-colonized root compared to the non-mycorhizal roots. This may be as a result of uptake and storage of arginine within AMF intraradical hyphae. Considering IRHP to BRHP ratio indicates that immunoreactivity percentage enhances by rising Pb levels. Immunoreactivity indicates a molecular configuration similar to the configuration of glomalin on hyphae. Our findings are in agreement with previous observations confirming that the toxicity-induced stress by metals may be enhancing glomalin production by AMF. The sequence of the glomalin gene revealed that is likely a 60-KDa heat-shock protein (Hsp) homolog. Glomalin relation with the heat shock proteins clarifies how stress is imposed by heavy metals may rapidly increase glomalin production by AMF and its concentrations in polluted soils.
Conclusion: The high contents of glomalin along with the increasing of Pb concentrations may be explained by the overexpression of this protein. This suggests that under Pb-induced stress and the toxic effect of Pb, the fungus exerts a protective mechanism against toxicant. Therefore, glomalin as a heat shock protein can involve in the reduction of possible cytosolic damages and the transfiguration of proteins under Pb toxicity. We can conclude that glomalin may reduce toxic elements availability via their stabilization and decrease their toxicity risk to other microorganisms and plants in heavy metal polluted sites.
samaneh ahmadi gheshlaghi
Abstract
Glomalin is a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, and is a major component of soil organic matter, which plays an important role in soil aggregation and carbon sequestration. Glomalin is produced only by the AM fungi. On the other hand, stressful environments such as salinity ...
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Glomalin is a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, and is a major component of soil organic matter, which plays an important role in soil aggregation and carbon sequestration. Glomalin is produced only by the AM fungi. On the other hand, stressful environments such as salinity can affect the AM fungi .The purpose of this study was to investigate the effect of NaCl salinity on glomalin production by Glomerales in symbiosis with corn plant. A factorial experiment was conducted in completely-randomized design (CRD) with four replications in a greenhouse. Factors were NaCl salinity with three levels (S0: 1.34, S1:4 and S2: 8 dS/m) and mycorrhizal fungi with four levels (non mycorrhizal, Glomus versiforme, G. intraradices, G. etunicatum). The results showed that the interaction of salinity and mycorrhizal fungi on plant dry weight, leaf proline, root colonization percentage, EEG and TG was significant at p
A. Maadani; A. Lakzian; Gh. Haghnia; R. Khorasani
Abstract
High concentration, of heavy metals and the presence of phosphorus in soils may cause a reduction in the growth and activity of arbuscular mycorrhizal (AM) fungi and consequently, the spore production of these fungi would decrease. In order to evaluate the effect of zinc and cadmium as heavy metals and ...
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High concentration, of heavy metals and the presence of phosphorus in soils may cause a reduction in the growth and activity of arbuscular mycorrhizal (AM) fungi and consequently, the spore production of these fungi would decrease. In order to evaluate the effect of zinc and cadmium as heavy metals and phosphorus on arbuscular mycorrhizal fungi activity through measuring glomalin produced by these fungi a factorial experiment arranged as completely randomized design was carried out. Experimental factors included two fungal species G. mosseae and G. intraradices and non mycorrhiza (NM), six combinations of metals (400 mg of Zn, 25 mg of Cd, 400 mg of Zn + 25 mg of Cd, 50 mg P, 50 mg of P+ 400 mg of Zn + 25 mg of Cd, and no metal kg-1 soil sample) in three replications. The results showed that inoculated treatments produced more glomalin compared to non mycorrhizal treatments. The application of Cd, Zn and P caused a significant reduction in produced glomalin by both fungi species. The most reduction of glomalin in G. intraradices was detected in Cd treatment and in G. mosseae was in Zn treatment. The result also showed a positive correlation between the measured glomalin by Bradford assay and the percent of root colonization. According to the results of this study, glomalin in soil could be an indicator to monitor arbuscular mycorrhizal fungi activity and soil health.
