Plants may control their own microbiomes

Plant leaves may seem unassuming, but beneath their glossy surfaces lies a surprising discovery: they are coated with a diverse array of RNA (ribonucleic acid) molecules.

This finding has the potential to reshape our understanding of plant biology and the interactions between plants and the environment.

The study was led by Lucía Borniego and Meenu Singla-Rastogi, postdoctoral fellows at Indiana University Bloomington, alongside Roger Innes, a professor of biology.

The research offers a fresh perspective on the complex relationships between plants and microbes.

“What excites us most about this discovery is that it indicates plants may control their microbiomes, in part, by regulating gene expression in microbes using cross-kingdom RNA interference, also known as RNAi,” said Innes.

But what does this mean, and why is it significant?

Revolutionary discovery: Plant RNAs on leaf surfaces

RNA, a fragile molecule, typically degrades quickly outside a cell unless protected. However, this study reveals that plants secrete viable RNA onto their leaf surfaces, where it remains surprisingly stable.

This discovery suggests that plant-derived RNA could directly influence microbial communities on leaf surfaces by engaging in cross-kingdom RNAi – a process whereby RNA from one organism affects gene expression in another.

Cross-kingdom RNAi is not new in biology. Scientists have known that organisms can exchange RNA to regulate genes. What’s remarkable here is the idea that plants may use this mechanism to interact with microbes that are colonizing their surfaces.

“Only recently has it been shown that RNAs produced by one organism can be taken up by another organism and then base pair with RNAs in the recipient organism,” Innes explained. RNA interference appears to occur in just about all living organisms.

Role of RNA and polysaccharides in plants

The research team found abundant RNAs on the leaf surfaces of Arabidopsis thaliana, a model plant widely used in scientific studies.

These RNAs were stable, likely because they formed condensates with polysaccharides, such as pectin.

As a component of the plant cell wall, pectin appears to play a protective role, ensuring that RNA molecules can persist outside plant cells.

The implications are profound. Stable RNA on leaf surfaces means that microbes colonizing these areas are exposed to plant RNA. This exposure could influence microbial gene expression, potentially determining which microbial species can thrive on leaf surfaces.

This ability to “curate” microbial communities could impact plant health, disease resistance, and overall growth.

Why does this matter? The bigger picture

The implications of this research extend far beyond plants.

“The manipulation of microbial communities by environmental RNA is likely taking place in our own guts as well, with RNA being secreted by our intestinal epithelial cells,” noted Innes.

This means that understanding plant-microbe interactions could shed light on similar processes in humans and other animals.

The connection doesn’t end there. Think about the salad you had for lunch. The RNA on the surface of those leafy greens could interact with your gut microbiome, influencing its composition and, potentially, your health.

While this hypothesis requires further research, it opens up fascinating possibilities about how our diets could impact our microbial ecosystems directly .

Potential applications in agriculture and medicine

This discovery isn’t just a scientific curiosity; it could have real-world applications. If plants can use RNA to influence microbial communities, farmers might one day harness this ability to enhance crop health.

For example, plants could be genetically engineered to secrete specific RNAs that discourage harmful microbes or promote beneficial ones.

In medicine, understanding how RNA influences microbial ecosystems could lead to new therapies. Imagine using RNA-based treatments to modulate the gut microbiome in patients with digestive disorders or metabolic diseases.

While these applications are speculative, the groundwork laid by this study provides a roadmap for possible future exploration.

Call for further research on plant RNA

While this study provides valuable insights, it also raises new questions.

How do specific RNAs influence microbial gene expression? Are there particular microbes that are more susceptible to RNA interference? And what environmental factors affect RNA stability on plant surfaces?

Additionally, the potential interaction between plant RNAs and the human microbiome deserves closer examination. Could consuming RNA-coated plants have measurable effects on human health?

Future research will need to address these questions to unlock the full potential of these findings.

A window into nature’s complexity

This discovery reminds us of nature’s intricate complexity. From the stability of RNA on plant surfaces to its potential to shape microbial communities, the study offers a glimpse into the complexity of hidden genetic mechanisms.

The research also highlights the interconnectedness of life on Earth – how plants, microbes, and even humans are linked by molecular interactions that transcend species boundaries.

“It is quite possible that RNA on leaf surfaces, like salad, could influence our own gut microbiomes,” said Innes.

This idea challenges us to rethink our relationship with plants, not just as sources of food or oxygen, but as active participants in a dynamic, interconnected biosphere.

The research was a collaborative effort. In addition to the Indiana University team, contributors included Patricia Baldrich and Blake C. Meyers from the University of California Davis, and Madison McGregor from the Donald Danforth Plant Science Center.

The interdisciplinary nature of this research makes it even more noteworthy. By combining biology, chemistry, and molecular genetics, the team uncovered a layer of plant-microbe interaction that had remained hidden until now.

The study is published in the journal Proceedings of the National Academy of Sciences.

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