Science finally learns what makes plant roots grow faster and stronger

In the vast kingdom of plants, roots serve as the vital “mouths” through which they absorb water and nutrients, anchor themselves, grow, and thrive in the face of environmental challenges.

Yet, the intricate mechanisms behind plant root growth have long remained a mystery. Now, an important study has solved this puzzle, revealing a surprising connection between plant root growth and a biological process familiar to those who practice fasting.

Autophagy is the hero of plant root growth

Researchers from the University of Copenhagen’s Department of Biology, led by Assistant Professor Eleazar Rodriguez, have discovered that a beneficial clean-up mechanism called autophagy plays a crucial role in the growth and strength of plant roots.

Autophagy, which is also present in humans and has gained popularity as part of a health trend, helps cells dispose of various waste products during periods without food.

“Fasting has become popular as it seems to have a range of health-promoting effects in humans, as periods without food cause the body to activate a clean-up processes to dispose of various waste products in cells,” explains Assistant Professor Eleazar 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 continued.

Understanding autophagy

The process of autophagy acts as a cellular recycling system, breaking down and repurposing old, damaged, or unnecessary components within the cell.

By doing so, autophagy maintains cellular health, promotes survival during stress, and plays a crucial role in various physiological processes.

Three types of autophagy

Cells carry out autophagy through three main pathways:

1. Macroautophagy: This is the most well-known form of autophagy, often referred to simply as “autophagy.” In this process, a double-membraned vesicle called an autophagosome engulfs cellular components and fuses with a lysosome, where the contents are degraded.
2. Microautophagy: In this process, the lysosome directly engulfs small portions of the cytoplasm, including proteins and organelles, through invaginations in its membrane.
3. Chaperone-mediated autophagy (CMA): This highly selective process targets specific proteins that contain a particular amino acid sequence. These proteins are recognized by chaperone proteins and directly transported into the lysosome for degradation.

Benefits of autophagy

Autophagy provides numerous benefits to cells and organisms:

• Cellular clean-up: By removing damaged or dysfunctional components, autophagy helps maintain cellular health and prevents the accumulation of toxic substances that can lead to disease.
• Nutrient recycling: During periods of starvation or stress, autophagy breaks down cellular components to generate energy and building blocks for essential processes.
• Immune defense: Autophagy plays a role in defending cells against invading pathogens, such as bacteria and viruses, by targeting them for degradation.
• Longevity: Increased autophagy has been linked to increased lifespan in various organisms, from yeast to mammals, likely due to its role in maintaining cellular health and preventing age-related diseases.

As research continues to uncover the complex mechanisms and far-reaching implications of autophagy, it becomes increasingly clear that this cellular self-cleaning process plays a vital role in maintaining health and preventing disease across various living organisms, from plants to humans.

Root growth has a heartbeat

It is well-known that auxin, a plant hormone, controls plant growth, including root growth. Auxin acts as a fuel for a kind of heartbeat that pulsates in each root tip of a plant.

Every four to six hours, auxin levels and the heartbeat in a plant’s roots reach a maximum, triggering the growth of new roots.

“The movement of a root is almost like watching a snake slithering forward in search of water and nourishment in the soil. And we can see that the heartbeat is strongest every time the root meanders forth,” says Eleazar Rodriguez.

Role of autophagy in plant root growth

To understand the significance of autophagy in root growth, the researchers disabled the clean-up mechanism in their experiments. The results were striking.

“In our experiments, we disabled the clean-up mechanism to understand its significance. Imagine if every garbage collector in Copenhagen went on strike –- it wouldn’t be long before trash filled the streets,” notes Rodriguez.

The scientists observed the exact same thing happening in the plant cells, as the heartbeats that drive root growth became much weaker and went out of sync.

This allowed the researchers to conclude that autophagy helps maintain the perfect balance of different biochemical components, enabling the most efficient root growth.

Implications for climate change

The new knowledge about plant roots could have significant implications in the fight against climate change. As extended periods of drought and floods become more common, food security is increasingly threatened. Crops with roots that can grow even in these harsh conditions are crucial.

“Numerous methods to change the genetic characteristics of plants are available today. These can be used to get plants to develop longer roots, faster, and in doing so, become more resistant to droughts or floods,” explains Ph.D. student Jeppe Ansbøl, a co-author of the study.

“One of the methods enlists the help of bacteria that live in symbiosis with the plant and can cause the plant to change its growth pattern. Several companies in Denmark are working on this right now,” noted Ansbøl.

The researchers believe that this new knowledge applies to all flowering plants and potentially more. In principle, crops like tomatoes, potatoes, rice, wheat, and corn could be altered to grow more and denser roots, thanks to this newfound understanding of how plants get their roots to grow.

Impact of plant root growth autophagy discovery

The discovery of the role of autophagy in plant root growth represents a significant step forward in our understanding of plants.

“The more roots the plants have the more water and nutrients they can take, so the plants grow better faster. We’re heavily dependent on plants because they feed us, extract CO2 from the atmosphere and produce the oxygen we breathe. As such, it is extremely important to understand them fully, to which end we have just taken a big step forward,” concluded Rodriguez.

In summary, by harnessing this new knowledge and applying innovative techniques, such as genetic modification and bacterial symbiosis, we can develop plants with more extensive and efficient root systems, better equipped to absorb water and nutrients in challenging environmental conditions.

As we continue to unravel the mysteries of plant biology, we move closer to ensuring food security and sustainability in an ever-changing world, reminding us of the vital importance of understanding the complex mechanisms that sustain life on our planet.

The full study was published in the journal EMBO Reports.

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