Recently, science advances published the”the key micro” from the research group of Professor Li Yi, School of life sciences, Peking UniversityThe research paper”nutrient copper orchestrates broad spectrum virus resistance in rice” (2022, Vol.8, issue 26.doi:10.1126/sciadv.abm0660) reveals the molecular mechanism of broad-spectrum virus resistance in rice mediated by the important trace element copper.
Rice is one of the most important food crops in China and the staple food of more than half of the world’s population. Rice virus disease transmitted by vector insects is one of the main diseases causing serious yield reduction of rice. Among them, rice stripe leaf blight caused by rice stripe virus (RSV) and rice dwarf virus (RDV) have repeatedly erupted in China, South Korea and Japan, seriously affecting the quality and safety of rice production. However, at present, the molecular response mechanism of rice after being infected by virus needs to be further studied, and there is also a lack of effective control methods in actual production.
Li Yi’s research group has focused on the interaction between viruses, host rice and vector insects for many years. Previous studies of the research group found that after RSV infects rice, virus coat protein (CP) can induce significant accumulation of jasmonic acid (Ja) content in plants, and jamyb, the key transcription factor of JA pathway, can bind and activate the promoter of ago18, the core factor of RNA silencing pathway, thereby inducing the expression of ago18 (Yang et al., 2020, cell host & microbe). On the one hand, ago18 can bind mir168 to inhibit its cleavage effect on ago1, so that ago1 can mediate antiviral immunity by binding viral siRNA (Wu et al., 2015, eLife); On the other hand, ago18 can also competitively bind mir528 with ago1, release ascorbic acid oxidase (AO), the target gene of mir528, regulate redox homeostasis in plants, promote the accumulation of reactive oxygen species (ROS), and thus enhance the antiviral immunity of rice (Wu et al., 2017, nature plants). In addition, the research group also found that the protein content of the transcription factor spl9 of mir528 decreased significantly after virus infection, so the accumulation of mir528 regulated by spl9 transcription activation decreased, which increased the expression of target gene AO and enhanced the antiviral ability of rice (Yao et al., 2019, molecular plant).
Recently, based on the above anti viral immunity of rice, Li Yi’s research group reported that the important trace element copper can enhance the anti viral ability of rice by inhibiting spl9. Copper ion is an important trace element for plants to grow normally and respond to adversity. Bordeaux liquid with copper ion as the main component is also widely used in agricultural production, but whether copper ion affects the antiviral ability of plants is still lack of research. Li Yi’s research team found that the genes encoding copper ion transport and copper ion binding protein were significantly induced or inhibited after the virus infected rice, and the copper ion transport mutants were more sensitive to the virus infection. In addition, the content and distribution of copper ions will change after the virus infects rice, and the virus infection can promote the accumulation of copper ions in the aboveground part of rice. Interestingly, although the total copper content of leaves increases after the virus infection, the copper content is measured by transmission electron microscopy energy dispersive spectroscopy and the structure of isolated sub cells. It is found that the virus infection will lead to the reduction of copper content in the intercellular space of rice, That is, more copper ions will enter the cell to play a role. Further research found that the anti-virus function of copper ion depends on the spl9-mir528-ao-ros pathway previously found by the research group. On the one hand, copper ion can inhibit the protein accumulation level of spl9 and the ability of spl9 to bind to mir528 promoter, so as to reduce the expression of mir528, and then enhance the accumulation of Ao and ROS level; On the other hand, copper ion can directly affect the enzyme activity of Ao. When the copper ion binding site of Ao is mutated, the anti-virus ability mediated by AO will also be inhibited. The study found that by directly exogenous application of copper ion or by gene editing technology to knock out the copper ion transport gene (copt7) in rice, the resistance of rice to virus can be enhanced by increasing the accumulation of copper ion and then regulating the spl9-mir528-ao pathway, which provides a potential idea for the practical application of copper ion antiviral. Importantly, the above anti-virus pathway mediated by copper ion has broad-spectrum resistance to different rice viruses (RSV and RDV), suggesting a broad application prospect of copper ion.
Dr. yaoshengze, a postdoctoral student of Peking University, and Kang Jinrui, a doctoral student, are the co first authors of the paper, and Li Yi is the corresponding author of the paper. Academician Xu Zhihong of Peking University and researcher Zhou Tong of Jiangsu Academy of agricultural sciences are the co authors of this paper. This research has been strongly supported by major projects of the National Natural Science Foundation of China, national key research and development plan and national rice industry system project.