A domestic research team has discovered a "molecular switch" that determines when plant leaves begin to age.
Researchers led by Professors Im Pyeong-ok, Lee Jong-chan, and Kim Min-sik in the Department of New Biology at Daegu Gyeongbuk Institute of Science and Technology (DGIST) said on the 27th that they "identified for the first time in the world a new operating principle in which RNA produced in the nucleus (the center of the cell) moves to the chloroplast to control leaf aging."
Chloroplasts in plants are organelles that generate energy needed for growth through photosynthesis. However, once leaves begin to age, chloroplasts break down on their own, and the resources within move to seeds, stems, or roots. These transferred resources become nutrients for the next generation or are used to prepare for growth in the next season.
This transition in which chloroplasts change from an "energy factory" to a "resource warehouse" is directly tied to plants' survival strategies, but the molecular signal that determines the timing has not been clearly identified.
Using Arabidopsis as a model plant, the research team discovered a new genetic signal that controls the aging of chloroplasts within leaves. In the process, they identified a molecule called "Chlorella RNA (CHLORELLA RNA)."
Instead of producing proteins, this RNA acts as a "regulatory RNA" that turns genes on or off. The research team confirmed that Chlorella RNA is produced in the nucleus and then moves to the chloroplast via the cytoplasm.
Once in the chloroplast, Chlorella RNA binds to the protein complex (PEP complex) that regulates gene expression within the chloroplast. Simply put, it serves as a switch that decides whether the chloroplast will "continue photosynthesis" or "self-degrade."
In other words, when there is a lot of Chlorella RNA, chloroplasts are active and maintain photosynthesis, and when the amount decreases, chloroplasts stop functioning and begin to break down.
The research team also identified the upstream regulator that controls the amount of Chlorella RNA, the "conductor," a GLK transcription factor. During the growth phase, GLK is highly active and produces a large amount of Chlorella RNA, resulting in green leaves and active photosynthesis. But once aging begins, GLK activity declines, Chlorella RNA decreases, chloroplasts degrade, and leaves turn yellow.
Im said, "This study is significant in that it identified when, where, and how RNA functions in a spatiotemporal manner," and added, "This approach not only forms the basis for understanding various life phenomena, but could also lead to research that controls leaf aging to improve photosynthetic efficiency and crop productivity."
The findings were published on the 10th in the international journal "Nature Plants."
References
Nat. Plants (2025), DOI: https://doi.org/10.1038/s41477-025-02129-z