The mechanism of nanosilver inhibition of Aspergillosis oryzae was elucidated

Rice with rice aspergillosis. Photo courtesy of the Institute of Rice, Chinese Academy of Agricultural Sciences

Recently, the research group of Kou Yanjun, a researcher at the Rice Research Institute of the Chinese Academy of Agricultural Sciences, discovered the cytological and molecular biological mechanism of nanosilver inhibiting Aspergillosis oryzae, and revealed the regulatory effect of nanosilver on rice aspergillosis synthesis, which provides a new idea for the use of nanosilver to control rice aspergillosis. The results were published in iScience.

Aspergillosis oryzae is a filamentous fungus that seriously endangers rice food security, and its infection of rice ears produces rice koji bulbs not only leads to a decrease in rice yield, but also contains a variety of toxins harmful to humans and animals, including rice chloronucleotin, threatening human health.

In recent years, the occurrence of rice aspergillosis in rice producing areas around the world has become more frequent, which has led people to pay more attention to the disease and develop effective fungicides against this pathogen. At present, nanomaterials have attracted more and more attention from researchers because of their good application prospects in the field of agricultural pest control. Among them, nanosilver is believed to be useful for the prevention and control of crop pathogens, because micromolar doses of nanosilver are sufficient to kill microbial pathogens. In addition, studies have reported that low doses of nanosilver can increase the yield and tillering of rice, which provides a positive theoretical basis for the application of nanosilver in the production of crop disease prevention and control, but the effect of nanosilver on rice pathogenic fungi is limited, and the molecular mechanism is unclear.

The researchers found that nanosilver has concentration-dependent properties on the growth inhibition of Aspergillosis oryzae, and half of the effective concentration of nanosilver can significantly inhibit the spore production and pathogenicity of Aspergillosis oryzae. Through the observation of the ultramicrostructure of cells, nanosilver destroyed the integrity of the cell wall and cell membrane structure of Aspergillosis oryzae. Further transcriptome data analysis showed that nanosilver affected multiple energy utilization and metabolic processes in Aspergillosis oryzae in transcriptional regulation, and the expression of genes related to rice chlorophycin synthesis was significantly upregulated.

Comparative transcriptome analysis showed that nanosilver treatment was significantly correlated with the gene regulated by the epirepressor UvKmt6, and the sensitivity of UvKmt6 knockout mutants to nanosilver was increased. Further biochemical experimental results showed that nanosilver activated the expression of genes related to rice powdery powder synthesis by reducing the level of H3K27me3 modification in Aspergillosis oryzae. In summary, this study proves that nanosilver regulates the growth and development, metabolism and pathogenicity of Aspergillosis oryzae by changing the cell structure and epigenetic modification-mediated transcriptional regulation of Aspergillosis oryzae.

On the one hand, this study confirmed that nanosilver is an effective nanofungicide for the prevention and control of rice aspergillosis, but on the other hand, it can also lead to the upregulation of the expression of mycotoxin synthesis genes. Therefore, in the future application of nanosilver, it is necessary to consider the combination of fungicides that inhibit mycotoxin synthesis to reduce the risk of toxin contamination.

The research was supported by the National Natural Science Foundation of China and the Key R&D Project of the China Rice Research Institute. (Source: Li Chen, China Science News)

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