Every seed starts with a simple goal: to reach water, collect nutrients, and stay upright. Below the surface, root tips probe the soil, extending into branches that keep the plant alive. Researchers have now traced the moment those branches appear to autophagy, the recycling pathway many associate with the health benefits of fasting.
Scientists at the University of Copenhagen mapped the pathway in living seedlings. They observed the transcription factor ARF7 disappear and return in predictable waves, each linked to a surge in the growth hormone auxin. "Fasting has become popular, as it appears to have a variety of health-promoting effects in humans, as periods without food cause the body to activate cleaning processes to get rid of various waste products in the cells," explains Assistant Professor Eleazar Rodriguez.
The process relies on NBR1, a tag that guides used proteins toward a vacuole for breakdown. Each ARF7 removal resets the signaling circuit so it can fire again a few hours later. When autophagy slows, ARF7 accumulates, messages run long, and the root loses its usual rhythm. The pattern resembles circadian rhythms that guide leaf opening but focuses solely on building the plant's hidden half.
The group disabled key autophagy genes to test the pathway's limits. Mutant seedlings produced fewer lateral roots and soaked up less water. "When we disrupted the plant's autophagy, there was waste everywhere, and we could detect the ARF7 protein among the waste," says Rodriguez. Microscopy revealed swollen vacuoles full of debris, resulting in a sparse and inefficient root system.
Because the recycling toolkit is shared among flowering plants, the findings open new options for breeders and companies developing microbial soil additives. Tuning autophagy or adjusting NBR1 tags could allow roots to pursue moisture deeper in the soil and capture fertilizer before it washes away, improving harvests without extra inputs. Pilot plots in Denmark are already testing these ideas under changing rain patterns.