Plants also trigger an 'autoimmune response' by mistaking their own protein structures for pathogens and attacking themselves. This is exemplified by the 'hybrid necrosis' phenomenon, where plants die on their own after crossbreeding between different varieties. An international collaborative research team, including Korea, revealed the cause and proposed strategies to predict and avoid this issue.
The Korea Advanced Institute of Science and Technology (KAIST), led by Professor Song Ji-jun, announced on the 21st that they have identified the structure and function of the protein complex 'DM3' that induces autoimmune responses in plants in collaboration with the National University of Singapore (NUS) and the University of Oxford.
The research team utilized cryo-electron microscopy (Cryo-EM). The significance of this study lies in identifying the cause of hybrid necrosis during crossbreeding between plant hybrids as 'defects in protein structure' due to abnormal responses of immune receptors.
The protein DM3 is originally an enzyme involved in the plant's immune response, but when it is part of a specific protein combination known as 'DANGEROUS MIX (DM),' the structure of DM3 protein is altered, causing issues. Notably, one variant of DM3, called 'DM3Col-0,' has six proteins that bind stably and are recognized as normal, thus not inducing an immune response.
In contrast, another variant, 'DM3Hh-0,' fails to properly bind the six proteins, causing the plant to recognize it as an abnormal state, triggering an immune alarm and inducing autoimmunity.
The research team observed the structure at atomic resolution using cryo-electron microscopy, revealing that the immune induction ability is due to differences in protein binding strength rather than the enzymatic function of DM3. This shows that plants can trigger an immune response not only when encountering 'external pathogens' but also when 'internal protein structures' change abnormally.
The research team explained that the results demonstrate how sensitive the plant immune system can be in response to changes in gene mixing and protein structure during crossbreeding of different plant varieties, leading to autoimmune reactions.
Dr. Kim Gi-jeong, the first author of the paper, said, 'Through international research cooperation, this high-quality study encompassing structural biochemistry, genetics, and cell biological experiments presents a new perspective on understanding plant immune systems.'
Professor Song Ji-jun, who led the research at KAIST's Department of Life Sciences, stated, 'The fact that the immune system can detect not only external pathogens but also structural abnormalities in its own proteins will set a new standard for plant biotechnology and crop breeding strategies.' He added, 'Cryo-electron microscopy-based structural analysis will become an important tool in understanding the nature of gene interactions.'
This research was published on the 17th in 'Molecular Cell,' a sister journal of the international academic journal 'Cell.'
References
Molecular Cell (2025), DOI: https://doi.org/10.1016/j.molcel.2025.06.021