scholarly journals Lon Protease of Azorhizobium caulinodans ORS571 Is Required for Suppression ofrebGene Expression

2012 ◽  
Vol 78 (17) ◽  
pp. 6251-6261 ◽  
Author(s):  
Azusa Nakajima ◽  
Toshihiro Aono ◽  
Shuhei Tsukada ◽  
Lowela Siarot ◽  
Tetsuhiro Ogawa ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Host Cells ◽  
Lon Protease ◽  
Bacterial Cells ◽  
Azorhizobium Caulinodans ◽  
Free Living ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity

ABSTRACTBacterial Lon proteases play important roles in a variety of biological processes in addition to housekeeping functions. In this study, we focused on the Lon protease ofAzorhizobium caulinodans, which can fix nitrogen both during free-living growth and in stem nodules of the legumeSesbania rostrata. The nitrogen fixation activity of anA. caulinodanslonmutant in the free-living state was not significantly different from that of the wild-type strain. However, the stem nodules formed by thelonmutant showed little or no nitrogen fixation activity. By microscopic analyses, two kinds of host cells were observed in the stem nodules formed by thelonmutant. One type has shrunken host cells containing a high density of bacteria, and the other type has oval or elongated host cells containing a low density or no bacteria. This phenotype is similar to apraRmutant highly expressing therebgenes. Quantitative reverse transcription-PCR analyses revealed thatrebgenes were also highly expressed in thelonmutant. Furthermore, alon rebdouble mutant formed stem nodules showing higher nitrogen fixation activity than thelonmutant, and shrunken host cells were not observed in these stem nodules. These results suggest that Lon protease is required to suppress the expression of therebgenes and that high expression ofrebgenes in part causes aberrance in theA. caulinodans-S. rostratasymbiosis. In addition to the suppression ofrebgenes, it was found that Lon protease was involved in the regulation of exopolysaccharide production and autoagglutination of bacterial cells.

scholarly journals phrR-Like Gene praR of Azorhizobium caulinodans ORS571 Is Essential for Symbiosis with Sesbania rostrata and Is Involved in Expression of reb Genes

2010 ◽  
Vol 76 (11) ◽  
pp. 3475-3485 ◽  
Author(s):  
Noriko Akiba ◽  
Toshihiro Aono ◽  
Hiroki Toyazaki ◽  
Satoru Sato ◽  
Hiroshi Oyaizu
Keyword(s):  
Nitrogen Fixation ◽  
Host Cells ◽  
Sesbania Rostrata ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Nitrogen Fixation Activity ◽  
Homologous Genes ◽  
Fixation Activity ◽  
Putative Transcription Factor ◽  
Infected Cells

ABSTRACT This study focuses on the function of the gene praR that encodes a putative transcription factor in Azorhizobium caulinodans ORS571, a microsymbiont of Sesbania rostrata. The praR gene is a homolog of the phrR gene of Sinorhizobium medicae WSM419, and the praR and phrR homologs are distributed throughout the class Alphaproteobacteria. The growth and nitrogen fixation activity of an A. caulinodans praR deletion mutant in the free-living state were not significantly different from those of the wild-type strain. However, the stem nodules formed by the praR mutant showed lower nitrogen fixation activity than the wild-type stem nodules. Microscopy revealed that infected host cells with an oval or elongated shape were observed at early stages in the nodules formed by the praR mutant, but these infected cells gradually fell into two types. One maintained an oval or elongated shape, but the vacuoles in these cells gradually enlarged and the bacteria gradually disappeared. The other cells were shrunken with bacteria remaining inside. Microarrays revealed that genes homologous to the reb genes of Caedibacter taeniospiralis were highly expressed in the praR mutant. Furthermore, the stem nodules formed by an A. caulinodans mutant with a deletion of praR and reb-homologous genes showed high nitrogen fixation activity, comparable to that of the wild-type stem nodules, and were filled with oval or elongated host cells. These results suggest that PraR controls the expression of the reb-homologous genes and that high expression of reb-homologous genes causes aberrance in A. caulinodans-S. rostrata symbiosis.

Confirmation of the infectivity of a free-living actinomycete isolated from Comptonia peregrina root nodules by immunological and ultrastructural studies

1978 ◽  
Vol 56 (21) ◽  
pp. 2621-2635 ◽  
Author(s):  
Maurice Lalonde
Keyword(s):  
Nitrogen Fixation ◽  
Pure Culture ◽  
Root Nodules ◽  
Free Living ◽  
Ultrastructural Studies ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Membrane Envelope ◽  
Freeze Etching

The inoculation of the host plant Comptonia peregrina (L.) Coult. (Myrica asplenifolia L.) by a pure culture of a free-living actinomycete, isolated from Comptonia root nodules by Callaham et al. (1978, Science, 199: 899–902), was successful. Short-term and long-term nodulation tests confirmed the infectivity of the Comptonia isolate. Acetylene reduction assays of the nodules induced by this prokaryote isolate demonstrated nitrogen fixation activity. This nitrogen fixation activity was able to sustain a prolific growth of the nodulated host plants growing in a N-free substrate. Indirect immufluorescence reactions, using specific gamma globulin against the actinomycetal isolate of the Comptonia root nodule, demonstrated the identity of this actinomycete in these in vitro produced Comptonia root nodules. Ultrastructure of the Comptonia isolate, developing as a free-living or endophytic actinomycete, was observed by light microscopy, freeze etching, and transmission electron microscopy. The free-living filamentous and sporulating isolate produced typical hyphae and vesicles when growing as an endophyte in the Comptonia nodule. These endophytic hyphae and vesicles were always encapsulated by a polysaccharide material which was surrounded by a host membrane envelope. A polysaccharide capsule was not demonstrated on the free-living Comptonia isolate. The endophytic vesicles were club shaped and highly septate. Such vesicles were never produced by the free-living isolate growing in an artificial medium. The Comptonia isolate is a spore former in pure culture and was able to sporulate in basal tissues of 5-month-old Comptonia nodules.

Environmental factors influencing the nitrogen fixation activity of free-living terrestrial cyanobacteria from a high arctic area, Spitsbergen

1999 ◽  
Vol 45 (7) ◽  
pp. 573-581 ◽  
Author(s):  
Turid Liengen
Keyword(s):  
Nitrogen Fixation ◽  
High Arctic ◽  
Nostoc Commune ◽  
Free Living ◽  
Terrestrial Cyanobacteria ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Field Samples ◽  
Anabaena Sp ◽  
Arctic Area

The influence of environmental factors on the nitrogen fixation activity of free-living, terrestrial cyanobacteria from a high arctic area were investigated using experimental manipulations with two different types of field samples, including macroscopic sheets of Nostoc commune and soil samples with a cyanobacterial crust from a Puccinellia salt marsh. In addition, a cultured Anabaena sp. previously isolated from the salt marsh was examined. Nitrogen fixation activity was measured using the acetylene reduction method. The nitrogen fixation mainly took place in the light, but even after 12 h incubation in darkness, low activities were maintained. Phosphorus fertilization stimulated the nitrogen fixation activity, and the highest activities were obtained with about 300 μM phosphate, both in the field samples and the cultured Anabaena sp. Ammonium (28 mM) immediately inhibited the nitrogen fixation activity of the cultured Anabaena sp, whereas 14 mM urea and 540 μM glutamate led to a weaker and slower inhibition of the nitrogen fixation activity, showing that the cultured Anabaena sp. was able to assimilate these combined nitrogen sources. Nitrate did not have any inhibitory effect on nitrogen fixation activity, either in the field samples or in the cultured Anabaena sp. Both the field samples and the cultured Anabaena sp. showed tolerance against sodium chloride concentrations corresponding to the concentration in seawater. The temperature optimum of the nitrogen fixation activity of the cultured Anabaena sp. was about 20°C. Key words: nitrogen fixation, cyanobacteria, Nostoc commune, Anabaena sp., high arctic.

scholarly journals Root Distribution and Nitrogen Fixation Activity of Tropical Forage Legume American Jointvetch (Aeschynomene americanaL.) cv. Glenn under Waterlogging Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Manabu Tobisa ◽  
Masataka Shimojo ◽  
Yasuhisa Masuda
Keyword(s):  
Nitrogen Fixation ◽  
Root Distribution ◽  
Water Surface ◽  
Nitrogenase Activity ◽  
Soil Surface ◽  
Nodule Formation ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Net Assimilation ◽  
Waterlogging Treatment

We investigated the root distribution and nitrogen fixation activity of American jointvetch (Aeschynomene americanaL.) cv. Glenn, under waterlogging treatment. The plants were grown in pots under three different treatments: no waterlogging (control), 30 days of waterlogging (experiment 1), and 40 days of waterlogging (experiment 2). The plants were subjected to the treatments on day 14 after germination. Root dry matter (DM) weight distribution of waterlogged plants was shallower than controls after day 20 of waterlogging. Throughout the study period, the total root DM weight in waterlogged plants was similar to that in the controls. Enhanced rooting (adventitious roots) and nodule formation at the stem base were observed in waterlogged plants after day 20 of waterlogging. The average DM weight of individual nodules on the region of the stem between the soil surface and water surface of waterlogged plants was similar to that of individual taproot nodules in the controls. Waterlogged plants had slightly greater plant DM weight than the controls after 40 days of treatment. The total nitrogenase activity (TNA) of nodules and nodule DM weight were higher in waterlogged plants than in the controls. Waterlogged American jointvetch had roots with nodules both around the soil surface and in the area between the soil surface and water surface after 20 days of waterlogging, and they maintained high nitrogenase activity and net assimilation rate that resulted in an increased growth rate.

scholarly journals The effect of inoculation of pea plants with mycorrhizal fungi and Rhizobium on nitrogen and phosphorus assimilation

2011 ◽  
Vol 52 (No. 10) ◽  
pp. 435-440 ◽  
Author(s):  
M. Geneva ◽  
G. Zehirov ◽  
E. Djonova ◽  
N. Kaloyanova ◽  
G. Georgiev ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Mycorrhizal Fungi ◽  
Glomus Mosseae ◽  
Rhizobium Leguminosarum ◽  
Glomus Intraradices ◽  
Plant Biomass ◽  
Phosphorus Level ◽  
Nitrogen And Phosphorus ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity

The study evaluated the response of pea (Pisum sativum cv. Avola) to arbuscular mycorrhizal fungi (AM) species Glomus mosseae and Glomus intraradices and Rhizobium leguminosarum bv. viceae, strain D 293, regarding the growth, photosynthesis, nodulation and nitrogen fixation activity. Pea plants were grown in a glasshouse until the flowering stage (35 days), in 4 kg plastic pots using leached cinnamonic forest soil (Chromic Luvisols – FAO) at P levels 13.2 (P1) and 39.8 (P2) mg P/kg soil. The obtained results demonstrated that the dual inoculation of pea plants significantly increased the plant biomass, photosynthetic rate, nodulation, and nitrogen fixation activity in comparison with single inoculation with Rhizobium leguminosarum bv. viceae strain D 293. On the other hand, coinoculation significantly increased the total phosphorus content in plant tissue, acid phosphatase activity and percentage of root colonization. The effectiveness of coinoculation with Rhizobium leguminosarum and Glomus mosseae was higher at the low phosphorus level while the coinoculation with Glomus intraradices appeared to be the most effective at higher phosphorus level.

scholarly journals Digalactosyldiacylglycerol Synthase Gene MtDGD1 Plays an Essential Role in Nodule Development and Nitrogen Fixation

2019 ◽  
Vol 32 (9) ◽  
pp. 1196-1209
Author(s):  
Zaiyong Si ◽  
Qianqian Yang ◽  
Rongrong Liang ◽  
Ling Chen ◽  
Dasong Chen ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Essential Role ◽  
Symbiotic Nitrogen Fixation ◽  
Histochemical Staining ◽  
Nodule Development ◽  
Nodule Number ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Infected Cells ◽  
Nodule Symbiosis

Little is known about the genes participating in digalactosyldiacylglycerol (DGDG) synthesis during nodule symbiosis. Here, we identified full-length MtDGD1, a synthase of DGDG, and characterized its effect on symbiotic nitrogen fixation in Medicago truncatula. Immunofluorescence and immunoelectron microscopy showed that MtDGD1 was located on the symbiosome membranes in the infected cells. β-Glucuronidase histochemical staining revealed that MtDGD1 was highly expressed in the infection zone of young nodules as well as in the whole mature nodules. Compared with the control, MtDGD1-RNA interference transgenic plants exhibited significant decreases in nodule number, symbiotic nitrogen fixation activity, and DGDG abundance in the nodules, as well as abnormal nodule and symbiosome development. Overexpression of MtDGD1 resulted in enhancement of nodule number and nitrogen fixation activity. In response to phosphorus starvation, the MtDGD1 expression level was substantially upregulated and the abundance of nonphospholipid DGDG was significantly increased in the roots and nodules, accompanied by corresponding decreases in the abundance of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. Overall, our results indicate that DGD1 contributes to effective nodule organogenesis and nitrogen fixation by affecting the synthesis and content of DGDG during symbiosis.

scholarly journals Nitrogen Fertilization Reduces Nitrogen Fixation Activity of Diverse Diazotrophs in Switchgrass Roots

2020 ◽  
pp. PBIOMES-09-19-0
Author(s):  
Rahul A. Bahulikar ◽  
Srinivasa R. Chaluvadi ◽  
Ivone Torres-Jerez ◽  
Jagadish Mosali ◽  
Jeffrey L. Bennetzen ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Fertilization ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity

scholarly journals EseE of Edwardsiella tarda Augments Secretion of Translocon Protein EseC and Expression of theescC-eseEOperon

2016 ◽  
Vol 84 (8) ◽  
pp. 2336-2344 ◽  
Author(s):  
Jia Yi ◽  
Shui Bing Xiao ◽  
Zhi Xiong Zeng ◽  
Jin Fang Lu ◽  
Lu Yi Liu ◽  
...  
Keyword(s):  
Gel Filtration ◽  
Host Cells ◽  
Edwardsiella Tarda ◽  
Supernatant Fraction ◽  
Bacterial Cells ◽  
Bacterial Survival ◽  
Content Type ◽  
Chaperone Protein ◽  
Pulldown Assay ◽  
Novel Protein

Edwardsiella tardais an important Gram-negative pathogen that employs a type III secretion system (T3SS) to deliver effectors into host cells to facilitate bacterial survival and replication. These effectors are translocated into host cells through a translocon complex composed of three secreted proteins, namely, EseB, EseC, and EseD. The secretion of EseB and EseD requires a chaperone protein called EscC, whereas the secretion of EseC requires the chaperone EscA. In this study, we identified a novel protein (EseE) that also regulates the secretion of EseC. AneseEdeletion mutant secreted much less EseC into supernatants, accompanied by increased EseC levels within bacterial cells. We also demonstrated that EseE interacted directly with EseC in a pulldown assay. Interestingly, EseC, EseE, and EscA were able to form a ternary complex, as revealed by pulldown and gel filtration assays. Of particular importance, the deletion ofeseEresulted in decreased levels of EseB and EseD proteins in both the bacterial pellet and supernatant fraction. Furthermore, real-time PCR assays showed that EseE positively regulated the transcription of the translocon operonescC-eseE, comprisingescC,eseB,escA,eseC,eseD, andeseE. These effects of EseE on the translocon components/operon appeared to have a functional consequence, since the ΔeseEstrain was outcompeted by wild-typeE. tardain a mixed infection in blue gourami fish. Collectively, our results demonstrate that EseE not only functions as a chaperone for EseC but also acts as a positive regulator controlling the expression of the translocon operonescC-eseE, thus contributing to the pathogenesis ofE. tardain fish.

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