Identification of Cbp1, a c-di-GMP Binding Chemoreceptor in Azorhizobium caulinodans ORS571 Involved in Chemotaxis and Nodulation of the Host Plant

Azorhizobium caulinodans ORS571 and Sinorhizobium teranga ORS51 and ORS52 are symbionts of the same host plant Sesbania rostrata. In nature, A. caulinodans nodulates more competitively the stem-located infection sites of Sesbania rostrata. Sinorhizobium strains, although frequently present in root nodules, are seldom found in stem nodules. One probable explanation for this phenomenon is the more abundant presence of Azorhizobium on the leaf and stem surfaces of the host plant. Work presented here hints at other plausible factors that determine the greater "stem specificity" of Azorhizobium. We found that under experimental conditions in which roots are not inoculated, all strains nodulated stems very well. However, ORS51 and ORS52 were much more sensitive than ORS571 to suppression of stem nodulation by previous root inoculation. The introduction of the regulatory nodD gene from A. caulinodans diminished the sensitivity to this suppression, probably by enhanced nod gene expression and subsequent Nod factor production. Our hypothesis is that the greater infectivity of ORS571 is due to a more efficient production of mitogenic Nod factors at stem-located infection sites, thereby more readily overcoming systemic suppression caused by previous root inoculations.Key words: autoregulation, nitrogen fixation, rhizobial ecology, systemic suppression of nodulation.

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FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

BMC Microbiology ◽

10.1186/s12866-021-02138-w ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Wei Liu ◽

Xue Bai ◽

Yan Li ◽

Haikun Zhang ◽

Xiaoke Hu

Keyword(s):

Signal Transduction ◽

Host Plant ◽

Type Strain ◽

Wild Type Strain ◽

Response Regulator ◽

Azorhizobium Caulinodans ◽

Wild Type ◽

Response Regulators ◽

Free Living ◽

Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

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COLONIZATION of Rubus glaucus BENTH BY AZORHIZOBIUM CAULINODANS ORS571 USIG A FLAVONOIDE NARINGENINA

BISTUA REVISTA DE LA FACULTAD DE CIENCIAS BASICAS ◽

10.24054/01204211.v2.n2.2016.2117 ◽

2016 ◽

Vol 14 (2) ◽

pp. 15

Author(s):

Giovani Orlando Cancino Escalante ◽

S E Cancino ◽

Enrique Quevedo Garcia

Keyword(s):

Bacterial Colonization ◽

Lateral Roots ◽

Plant Growth Promoting Bacteria ◽

Azorhizobium Caulinodans ◽

Intensity Parameters ◽

Plant Growth Promoting ◽

Measuring Frequency ◽

Northwest Region ◽

Azorhizobium Caulinodans Ors571

Root systems of two Andean blackberry materials (thorn and thornless) of Rubus glaucus Benth cultured in vitro in the presence of five treatments (four flavonoids and one control) were inoculated with Azorhizobium caulinodans ORS571 (pXLGD4) (a strain carrying the lacZ reporter gene which facilitated the detection of bacterial colonization). Evaluation of colonization effectiveness for each treatment was done by means of application of experimental design measuring frequency and intensity parameters. Statistical analysis showed differences at comparing flavonoids vs. control and the overall higher effectiveness of the flavonoid naringenin. Observation of colonization was made by light and electron microscope confirming internal colonization of Andean blackberry roots by A. caulinodans. This is the first work demonstrating root colonization of R.glaucus by azorhizobia and therefore settling the basis for future investigations and scientific applications related to interaction with plant growth-promoting bacteria under the effect of flavonoids, along with possible implications of common benefit for non-legume crops in the northwest region of Colombia. Key Words: Azorhizobium caulinodans ORS571, Andean blackberry, flavonoids, LacZ, lateral roots, naringenin.

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Nucleotide sequence of the fixABC region of Azorhizobium caulinodans ORS571: similarity of the fixB product with eukaryotic flavoproteins, characterization of fixX, and identification of nifW

MGG Molecular & General Genetics ◽

10.1007/bf00261695 ◽

1991 ◽

Vol 225 (3) ◽

pp. 514-520 ◽

Cited By ~ 36

Author(s):

Fabrizio Arigoni ◽

P. Alexandre Kaminski ◽

Hauke Hennecke ◽

Claudine Elmerich

Keyword(s):

Nucleotide Sequence ◽

Azorhizobium Caulinodans ◽

Azorhizobium Caulinodans Ors571

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Glutaredoxins Play an Important Role in the Redox Homeostasis and Symbiotic Capacity of Azorhizobium caulinodans ORS571

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-04-20-0098-r ◽

2020 ◽

Vol 33 (12) ◽

pp. 1381-1393

Author(s):

Yajun Cao ◽

Gaofei Jiang ◽

Mingxu Li ◽

Xingxing Fang ◽

Dan Zhu ◽

...

Keyword(s):

Redox State ◽

Bacterial Resistance ◽

Redox Homeostasis ◽

Sesbania Rostrata ◽

Limited Information ◽

Azorhizobium Caulinodans ◽

Cellular Redox ◽

Symbiotic Associations ◽

Functional Analyses ◽

Azorhizobium Caulinodans Ors571

Glutaredoxin (GRX) plays an essential role in the control of the cellular redox state and related pathways in many organisms. There is limited information on GRXs from the model nitrogen (N2)-fixing bacterium Azorhizobium caulinodans. In the present work, we identified and performed functional analyses of monothiol and dithiol GRXs in A. caulinodans in the free-living state and during symbiosis with Sesbania rostrata. Our data show that monothiol GRXs may be very important for bacterial growth under normal conditions and in response to oxidative stress due to imbalance of the redox state in grx mutants of A. caulinodans. Functional redundancies were also observed within monothiol and dithiol GRXs in terms of different physiological functions. The changes in catalase activity and iron content in grx mutants were assumed to favor the maintenance of bacterial resistance against oxidants, nodulation, and N2 fixation efficiency in this bacterium. Furthermore, the monothiol GRX12 and dithiol GRX34 play a collective role in symbiotic associations between A. caulinodans and Sesbania rostrata. Our study provided systematic evidence that further investigations are required to understand the importance of glutaredoxins in A. caulinodans and other rhizobia.

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