On May 15, Beijing time, the team of Wang Ertao, Zhang Yu and Academician He Zuhua of the Center for Excellence in Molecular Plant Science of the Chinese Academy of Sciences made a major breakthrough in the study of rice immune mechanism. The results were published in the top international academic journal Nature with the title of "Release of a ubiquitin brake activates OsCERK1-triggered immunity in rice", laying a theoretical foundation for a deeper understanding of how plants skillfully use the double-edged sword of the immune system to coordinate the balance of disease resistance, symbiosis and growth.
Research background
Background:
Rice is the main food crop in the mainland, and the main challenges in its production include: 1. Rice is often infested by pathogenic fungi such as rice blast fungus during the growth process, and over-reliance on chemical pesticides, thus posing a serious threat to the environment and food safety. Second, rice has a huge demand for nutrients such as phosphorus and nitrogen, which leads to excessive fertilization and serious environmental pollution. Therefore, it is one of the important directions of crop breeding to explore the mechanism of rice immunity and symbiosis, and improve crop disease resistance and nutrient absorption.
It is worth noting that arbuscular mycorrhizal fungi, which promote nutrient absorption and growth in rice, and rice blast fungus, which causes devastating diseases to rice, are both fungi. Their cell surfaces are covered with a polysaccharide called chitin. So how do plants distinguish between 'beneficial' and 'harmful' microbes? It turns out that 'long and short are different': short-chain chitin can act as a symbiotic signal, while long-chain chitin triggers the plant's disease-fighting immune response. When establishing a mutually beneficial symbiotic relationship, the symbiotic mycorrhizal fungus releases a large amount of short-chain chitin as a signal to inform the plant to prepare for the establishment of a symbiotic relationship. Pathogenic bacteria, on the other hand, try to avoid the "leakage" of chitin molecules, especially long-chain chitin, so as not to be recognized by plants and activate the immune response. OsCERK1, a key receptor protein on the surface of rice cells, can distinguish immune signals or symbiotic signals, and specifically mediate plant immune or symbiotic responses. However, this also requires some regulation, as if the immune response triggered by the receptor OsCERK1 is out of control, it will trigger an excessive immune response, which will increase resistance to pathogens but also hinder plant growth and the establishment of symbiosis with reciprocal mycorrhizae. How to effectively regulate this potentially overactivated immune response in rice has long been a mystery to be uncovered by the scientific community.
Plants are able to recognize the length of polymerization of chitin polysaccharides in fungal cell walls, thus distinguishing pathogenic bacteria from beneficial bacteria
Research content
Outline of Research
A regulatory protein called OsCIE1 was found to bind OsCERK1 kinase activity. In the absence of pathogen infection, OsCIE1 can act like a "brake" to attach a small protein molecule called ubiquitin to the surface of OsCERK1 protein, inhibiting the kinase activity of OsCERK1 and preventing immune overactivation. However, when rice is faced with pathogenic fungal invasion, long-chain chitin on the fungal cell wall rapidly induces kinase activity of OsCERK1. This kinase adds a phosphate molecule to a key region on the surface of the OsCIE1 protein, inhibiting OsCIE1's ability to restrain OsCERK1, thereby releasing the "brake". At this time, the immune signaling pathway is successfully activated by OsCERK1, which initiates the plant immune response and resists the infection of pathogenic bacteria.
Through the collaborative use of structural biology methods, the researchers accurately identified Ser237, the key site that controls the tightening of the OsCIE1 "brake". When Ser237 is phosphorylated by OsCERK1, OsCERK1 can show its power and actively defend against external enemies, just like the failure of the brake brake. Once Ser237 is not phosphorylated, the brake brake works again and OsCERK1 returns to calm.
Ser237是OsCIE1的活性开关
While resisting foreign enemies, OsCERK1 controls the establishment of mycorrhizal symbiosis in rice, allowing arbuscular mycorrhizal fungi to enter the plant root system, and using its developed mycorrhizal network to assist rice in absorbing key nutrients such as phosphorus and nitrogen more efficiently, and promoting the growth and development of rice. Therefore, this study revealed the role of OsCIE1 in plant immunity and symbiosis, which not only clarified the molecular mechanism of plant synergistic regulation of immunity, symbiosis, growth and development, but also provided genetic resources for future green agricultural production.
Schematic diagram of the mechanism by which the ubiquitin protein "brake" mediated by OsCIE1 regulates OsCERK1 co-production/immune homeostasis
Related information
Related information
Prof. Wang Ertao, Prof. Zhang Yu and Academician He Zuhua of the Center of Excellence for Molecular Plants are the co-corresponding authors of the article, and Wang Gang, a postdoctoral fellow in Wang Ertao's research group, Chen Xi, a doctoral student, and Yu Chengzhi, a graduate doctoral student in Zhang Yu's research group, are the co-first authors. Ertao Wang's research team has been committed to innovative research on the symbiosis and application of plants and microorganisms for many years, and has achieved fruitful research results in this field. Their research work not only revealed the molecular mechanism of plant recognition to distinguish symbiotic bacteria from pathogenic bacteria, but also laid a solid foundation for crops to efficiently obtain nutrients through microorganisms.
At the forefront of plant science, focusing on the frontier progress of plant science, the release of information, recruitment information and method software sharing. For submission and recruitment, please reply to "Submission" in the background, which are free of charge; For business cooperation, please contact WeChat ID: zwkxqy;