Related Experiment Video
Updated: Jan 23, 2026
Obtaining Hemocytes from the Hawaiian Bobtail Squid Euprymna scolopes and Observing their Adherence to Symbiotic and Non-Symbiotic Bacteria
Published on: February 11, 2010
Antioxidation and symbiotic nitrogen fixation function of prxA gene in Mesorhizobium huakuii
Sanjiao Wang1, Tiantian Lu1, Qiang Xue1
1College of Life Sciences, South-Central University for Nationalities, Wuhan, Hubei, China.
Abstract:
Peroxiredoxins (Prxs) play an essential role in the antioxidant activity and symbiotic capacity of Mesorhizobium huakuii. A mutation in the M. huakuii prxA gene (encoding a Prx5-like peroxiredoxin) was generated by homologous recombination. The mutation of prxA did not affect M. huakuii growth, but the strain displayed decreased antioxidative capacity under organic cumene hydroperoxide (CUOOH) conditions. The higher resistance of the prxA mutant strain compared with the wild-type strain to more than 1 mmol/L H2 O2 was associated with a significantly higher level of glutathione reductase activity and a significantly lower level of intracellular hydrogen peroxide content. Real-time quantitative PCR showed that under 1 mmol/L H2 O2 conditions, expression of the stress-responsive genes katG and katE was significantly upregulated in the prxA mutant. Although the prxA mutant can form nodules, the symbiotic ability was severely impaired, which led to an abnormal nodulation phenotype coupled to a 53.25% reduction in nitrogen fixation capacity. This phenotype was linked to an absence of bacteroid differentiation and deregulation of the transcription of the symbiotic genes nifH, nifD, and fdxN. Expression of the prxA gene was induced during symbiosis. Thus, the PrxA protein is essential for antioxidant capacity and symbiotic nitrogen fixation, playing independent roles in bacterial differentiation and cellular antioxidative systems.
Insights
The Mesorhizobium huakuii prxA gene is crucial for antioxidant defense and symbiotic nitrogen fixation. Its mutation impairs bacterial antioxidant capacity and severely reduces symbiotic ability.
Area of Science:
- Microbiology
- Plant-microbe interactions
- Biochemistry
Background:
- Peroxiredoxins (Prxs) are vital for antioxidant activity and symbiosis in Mesorhizobium huakuii.
- The prxA gene encodes a Prx5-like peroxiredoxin essential for these functions.
Purpose of the Study:
- To investigate the role of the M. huakuii prxA gene in antioxidant capacity and symbiotic nitrogen fixation.
- To elucidate the specific functions of the PrxA protein in bacterial differentiation and cellular antioxidative systems.
Main Methods:
- Homologous recombination was used to generate a prxA mutant strain.
- Antioxidative capacity was assessed under cumene hydroperoxide (CUOOH) and hydrogen peroxide (H2O2) stress.
- Gene expression was analyzed using real-time quantitative PCR (RT-qPCR).
- Symbiotic ability and nitrogen fixation were evaluated, including nodulation phenotype and expression of symbiotic genes.
Main Results:
- The prxA mutation did not affect bacterial growth but reduced antioxidative capacity under CUOOH stress.
- The mutant showed increased resistance to H2O2, associated with higher glutathione reductase activity and lower intracellular H2O2.
- Expression of stress-responsive genes katG and katE was upregulated in the prxA mutant under H2O2 stress.
- Symbiotic ability was severely impaired, with reduced nitrogen fixation, absence of bacteroid differentiation, and deregulation of symbiotic genes (nifH, nifD, fdxN).
- prxA gene expression was induced during symbiosis.
Conclusions:
- The PrxA protein is essential for both antioxidant capacity and symbiotic nitrogen fixation in M. huakuii.
- PrxA plays independent roles in bacterial differentiation and cellular antioxidative systems.
- The prxA gene is upregulated during symbiosis, highlighting its importance in the symbiotic relationship.
Related Concept Videos
01:49The Nitrogen Cycle
01:20Overview of Nitrogen Metabolism
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
01:03Fixation and Sectioning
The simplest type of preparation is the wet mount, in which the specimen is placed in a drop of liquid on the slide. A liquid specimen can be directly deposited on the slide using a dropper. Solid specimens, such as skin scraping, can be placed on the slide before adding a drop of liquid to prepare the wet mount. Sometimes the liquid is simply water, but stains are often added...
01:22Inorganic Nitrogen Assimilation
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
01:12Loss of Tumor Suppressor Gene Functions
When the tumor suppressor genes develop mutations or are lost, cells start growing out of control, leading to cancer. However, a single functional copy of the tumor suppressor gene is enough for the cells to maintain their normal functions and cell...