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Plant roots are essential “mouths” through which they take in water and nutrients, attach themselves, grow, and resist environmental challenges.
However, the complex mechanisms behind the formation of plant roots have long remained enigmatic. This mystery has now been solved by an important study, which has shown an unexpected connection between the development of plant roots and biological processes that people are familiar with.
Autophagy is the hero of plant root growth
Led by Assistant Professor Elizar Rodríguez, biologists from the University of Copenhagen’s Department of Biology have shown that autophagy – a useful cleaning mechanism – is essential for the development and strengthening of plant roots.
During times when food is scarce, autophagy – which is also observed in humans – helps cells get rid of various waste products. It is becoming more and more popular as a health fad.
“Fasting has become popular because of its health-promoting effects in humans, as periods without food activate the body’s cleaning processes to dispose of various waste products in cells,” says Assistant Professor Elizar Rodriguez.
“In our study, we have proven that the same mechanism, which also exists in the plant kingdom, plays a vital role in the ability of plant roots to grow and absorb water and nutrients for the rest of the plant,” Rodriguez said.
Understanding autophagy
As a kind of internal recycling mechanism, autophagy breaks down and regenerates unused, damaged or expired parts of the cell.
By doing so, autophagy supports survival under stressful conditions, maintains cellular health, and is essential for many physiological functions.
Three types of autophagy
There are three primary pathways used by cells to carry out autophagy:
- Macroautophagy: The most well-known form of autophagy is macroautophagy, sometimes referred to simply as “autophagy”. During this process, cellular components are engulfed in double-membrane vesicles known as autophagosomes, which then fuse with lysosomes to degrade its contents.
- Microautophagy: During this process, the lysosome invades its membrane to absorb proteins and organelles directly into the cytoplasm within minutes.
- Chaperone-mediated autophagy (CMA): It is a highly selective mechanism that targets specific proteins with specific amino acid sequences. Chaperone proteins recognize these proteins and transport them directly to lysosomes where they are degraded.
Benefits of autophagy
Autophagy provides numerous benefits to cells and organisms:
- Cellular Cleanup: Autophagy helps maintain cellular health by removing defective or damaged components and stopping the accumulation of toxins that can cause disease.
- Nutrient recycling: Autophagy breaks down cellular components to provide energy and building blocks for vital functions during times of stress or starvation.
- Immune defense: By focusing on their breakdown, autophagy helps protect cells from invasive diseases such as bacteria and viruses.
- Longevity: Because autophagy plays an important role in maintaining cellular health and preventing age-related disorders, it has been linked to longevity in various species, including mammals and yeast.
With ongoing investigations into the complex function and broad implications of autophagy, it is becoming increasingly clear that this process of cellular self-purification is essential.
Root growth has a heartbeat
Auxin, a plant hormone, is widely known to regulate plant development, particularly root growth. The root tip of every plant has a heartbeat that is powered by auxin.
Auxin levels and the heartbeat of the plant’s roots increase every four to six hours, prompting the emergence of new roots.
“Observing the movement of the root is like a snake crawling through the earth in search of moisture and food. Elizar Rodríguez explains, “and we can see that every time the root comes out, the heartbeat is the strongest.”
Role of autophagy in plant root growth
In their experiments, the researchers blocked the clean-up system to better understand the role of autophagy in root development. The results were remarkable.
To determine the importance of the cleaning process, we stopped it in our study. Rodríguez observes that if every garbage collector in Copenhagen goes on strike, it won’t take long for garbage to spread to the streets.
The heartbeats that drive root growth were significantly weakened and out of rhythm, and the scientists observed the exact same thing happening in plant cells.
This led the researchers to conclude that autophagy contributes to the maintenance of an ideal balance between various biochemical factors, which facilitates the most efficient root development.
Implications for climate change
An increased understanding of plant roots can have a significant impact on the fight against climate change. Prolonged droughts and frequent floods threaten food security. Crops with roots that can withstand these severe conditions must be planted.
It is now possible to alter the genetic makeup of plants using a variety of techniques. This can be used to encourage trees to grow roots more quickly, making them more resilient to floods and droughts,” says study co-author and Ph.D. candidate Jeppe Ansboll.
“One technique uses bacteria that live in symbiosis with the plant and have the ability to alter the plant’s growth pattern. Currently, several Danish businesses are working on this.
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