Recently, Professor Han Heyou’s research group from the State Key Laboratory of Agricultural Microbiology of Huazhong Agricultural University published a report entitled”Cobalt Ferrite Nanozyme for Efficient” in Environmental Science-nano. Symbiotic Nitrogen Fixation via Regulating Reactive Oxygen metabolism” research paper. This paper reported a cobalt ferrite nanozyme (CoFe2O4-NPs) with antioxidant activity, and analyzed its mechanism in regulating the synergistic effect of soybean symbiotic nitrogen fixation.
The application of chemical nitrogen fertilizer has played a huge role in supplementing crop nitrogen nutrition, increasing crop yield, and ensuring food security. However, in recent years, it has been linked to the ecological environment and The contradiction of sustainable agricultural development has become increasingly prominent. Therefore, it is imperative to seek a new source of nitrogen that is highly efficient and environmentally friendly.
Biological nitrogen fixation provides 75%of the nitrogen for global plants. It is one of the major basic research topics in life sciences and plays an important role in production practice. And photosynthesis are collectively referred to as the cornerstone of life activities on earth, providing a new way to reduce the use of chemical nitrogen fertilizers, alleviate environmental pollution, maintain ecological balance, and reduce agricultural production costs. In nature, biological nitrogen fixation is catalyzed by nitrogenase, which is an enzyme complex containing iron-molybdenum cofactor (FeMo). It is very sensitive to reactive oxygen species (ROS). Excessive ROS can irreversibly inactivate nitrogenase. Therefore, the reasonable regulation of ROS plays a decisive role in the efficiency of rhizobia-legume symbiosis nitrogen fixation.
Nanozyme regulation of symbiotic nitrogen fixation schematic diagram< /span>
Professor Han Heyou’s team built a natural nitrogen fixation system through simulation and introduced functional nanoenzymes for comparative studies and found that CoFe2O4-NPs has excellent peroxidase activity (Figure 1 ). By introducing CoFe2O4-NPs nanoenzymes into the nitrogen fixation system, it can effectively alleviate the oxidative stress of ROS generated in the nitrogen fixation process to nitrogenase, and increase the accumulation of leghemoglobin, providing a better environment for the parasitism of rhizobia, thereby increasing the rhizobia Parasitism, and ultimately achieve a significant increase in nitrogenase activity.
Figure 2. In vitro activity of CoFe2O4-NPs nanozyme Verification
In this study, the researchers first verified the in vitro activity of CoFe2O4-NPs nanozymes and found that at low concentrations, CoFe2O4-NPs showed excellent performance. The oxidase activity and the fitted Michaelis constant confirmed its enzymatic activity, and the reactive oxygen staining experiment further confirmed its ROS scavenging ability (Figure 2).
CoFe2O4 nanozyme on the biological activity of rhizobia and the effect of nitrogen fixation-related gene expression
was observed through microsections, bacterial viability staining and transmission electron microscopy, and found that the introduction of CoFe2O4 nanozyme significantly increased the density of rhizobia. Further detection of the expression analysis of related nitrogen-fixing genes (GmnifA, GmnifD, GmnifH, GmnifK) confirmed that Rhizobium was up-regulated under the conditions of CoFe2O4-NPs treatment (Figure 3).
The effect of CoFe2O4-NPs nanozyme on ROS content< /span>
Researchers are still in the developmental stage of soybean nodules, observe and quantitatively analyze half of the nodules, and find that the leghemoglobin accumulation is obvious Increased; in the in situ and quantitative analysis of nodule ROS, it was found that the content of CoFe2O4-NPs was significantly reduced (Figure 4). This research is another new advance in the research of carbon-based nanozymes in the research group to promote the symbiotic nitrogen fixation of legumes (Nanoscale, 2017; 9:9921-9937), which provides a new idea for promoting the nodulation of legumes and further broadens the The application prospects of enzymes in agriculture.
Ma Jun and Associate Professor Song Zhiyong, PhD students in the School of Science of our school, are the co-first authors of the paper, Professor Han Heyou is the corresponding author, and Associate Professor Wang Youning from the School of Plant Science and Technology is also Participate in the research. The research was funded by the National Natural Science Foundation of China.