The secret to disarming plant pathogens revealed

Unravelling the role of bacterial proteins in plant diseases! Disarming plant diseases one protein at a time! Scientists may have found a means to neutralise them, saving farmers $220 billion in yearly crop losses.

The impact of plant diseases on global food production

Bacteria have long been known to wreak havoc on crops, threatening our food supply and causing substantial economic losses. For over two decades, biologist Sheng-Yang He and his dedicated team have been delving into the mysterious world of bacterial proteins, seeking to unravel their role in plant diseases that plague countless crops worldwide.

Finally, a breakthrough has been achieved after years of tireless research and collaboration. In a groundbreaking study published in the esteemed journal Nature, he and his colleagues have uncovered the mechanisms by which these proteins induce disease in plants and devised a method to neutralise their harmful effects.

Understanding the mechanism of harmful proteins

Their investigation focused on a group of injected proteins called AvrE/DspE, responsible for causing diseases ranging from brown spots in beans to fire blight in fruit trees. Despite their significance, the exact workings of these proteins have long remained elusive.

The researchers discovered that these proteins adopt a unique 3D structure resembling a tiny mushroom with a cylindrical stem through cutting-edge advancements in artificial intelligence and innovative experimental techniques. Intriguingly, this structure resembled a straw, leading the team to hypothesise that the proteins create channels in plant cells, enabling the bacteria to extract water from the host during infection.

Further investigation into the 3D model of the fire blight protein revealed that its hollow inner core contains many proteins from the AvrE/DspE family. These proteins were found to suppress the plant's immune system and induce dark water-soaked spots on leaves, the telltale signs of infection.

However, armed with this newfound knowledge, the researchers sought to develop a strategy to disarm these proteins and halt their destructive effects. They turned to poly(amidoamine) dendrimers (PAMAM), tiny spherical nanoparticles with precise diameters that can be tailored in the lab. By experimenting with different sizes, they identified a nanoparticle that effectively blocked the water channels formed by the bacterial proteins.

Application of nanoparticles in blocking water channels

In a remarkable series of experiments, the researchers treated frog eggs engineered to produce the water channel protein with these channel-blocking nanoparticles. The results were astounding—the eggs no longer swelled with water and remained unaffected. Similarly, infected Arabidopsis plants treated with the nanoparticles significantly reduced pathogen concentrations, effectively preventing disease development.

This breakthrough discovery offers a glimmer of hope in the battle against plant diseases, which cause immense losses in global food production. Plants are responsible for 80% of the world's food supply, and protecting them from pathogens and pests is crucial for ensuring food security.

The team's groundbreaking research on plant pathogens and their harmful proteins opens up new possibilities for combating various plant diseases. The implications of their findings extend far beyond a single crop or disease, offering novel approaches to address a wide range of plant diseases. By understanding the mechanism by which bacterial proteins, such as AvrE and DspE, cause diseases in plants, researchers can now explore strategies to disarm these proteins and prevent their harmful effects.

The team discovered that these proteins act as water channels, allowing bacteria to invade plant cells and create a saturated environment that promotes their growth. This insight led to the development of channel-blocking nanoparticles, effectively preventing bacteria from infecting plants and causing disease symptoms. Using precise nanoparticles, such as PAMAM dendrimers, to block plant pathogens' water channels represents a promising avenue for crop protection.

Figure 1: this figure shows that PAMAM are very branched polymers that are very small, have a low polydispersity index, and have a lot of active amine functional groups. They have multiple modifiable surface functionalities, facilitating the conjugation of ligands for cancer targeting, imaging, and therapy. PAMAM dendrimers also have solubilisation, high drug encapsulation, and passive targeting ability, contributing to their therapeutic success. Cancer researchers are excited about their potential as drug carriers and non-viral gene vectors, with a focus on diagnostic imaging applications.

These nanoparticles can be tailored to specific diameters, allowing for targeted disruption of the bacterial proteins' channels. The nanoparticles effectively render the bacteria harmless by interfering with the proteins' ability to create a moist environment within plant cells. This innovative approach has shown success in combating diseases caused by pathogens like Pseudomonas syringae and Erwinia amylovora.

Implications for global food production and food security

The potential impact of this research on global food production is immense. Plant diseases result in significant crop losses, amounting to over 10% of global food production annually. This translates to a staggering $220 billion economic loss worldwide. Developing strategies to disarm harmful proteins and protect crops from diseases can mitigate these losses and enhance food security.

Furthermore, the team's findings highlight the critical role of plant biology research in addressing global challenges. Plants provide 80% of our food, making their health and protection crucial for sustaining our growing population. By understanding how pathogens infect plants and developing innovative solutions, we can safeguard our food supply and reduce the economic impact of crop diseases.

Experimental results and a promising outlook

The researchers aim to further investigate the interaction between channel-blocking nanoparticles and bacterial proteins. By visualising the structures and mechanisms involved, they hope to refine their designs and develop even more effective strategies for crop protection.

Additionally, artificial intelligence, such as the AlphaFold2 programme, has proven instrumental in predicting the 3D structures of complex proteins. Continued advancements in AI technology will undoubtedly contribute to further breakthroughs in understanding and combating plant diseases.

By unravelling the mechanisms by which harmful proteins cause diseases in plants and developing innovative strategies to disarm them, we can protect global food production and enhance food security. The implications of this research extend beyond a single crop or disease, paving the way for novel approaches to combat a wide range of plant diseases and safeguard our agricultural systems.

Conclusion

The groundbreaking research conducted by biologist Sheng-Yang He and his team offer hope in the fight against plant diseases. By revealing the mechanisms by which harmful proteins cause diseases in plants and developing innovative strategies to disarm them, they have paved the way for novel approaches to combat various plant diseases. This enhances food security and protects global food production, reducing economic losses and ensuring a sustainable future.

With continued advancements in artificial intelligence and the development of precise nanoparticles, the possibilities for further breakthroughs in understanding and combating plant diseases are endless. By safeguarding our agricultural systems, we can secure the health of our crops and, ultimately, the well-being of our growing population. The implications of this research extend far beyond agriculture, offering new avenues for addressing global challenges and paving the way for a brighter and more resilient future.

Figure 2: this figure shows a working model for the molecular actions of AvrE-family effectors in plants. AvrE-family effectors are water- and solute-permeable channels that change the osmotic and water potential and make an apoplast that is rich in water and nutrients for bacteria to grow in plant tissues that are infected. They can also engage host proteins to modulate AvrE-family channel properties or optimise pathogenic outcomes.

Written by Sara Maria Majernikova

Related articles: Digital innovation in rural farming / Nanomedicine / Mechanisms of pathogen evasion

REFERENCE

Kinya Nomura, Felipe Andreazza, Jie Cheng, Ke Dong, Pei Zhou, Sheng Yang He. Bacterial pathogens deliver water- and solute-permeable channels to plant cells. Nature, 2023; DOI: 10.1038/s41586-023-06531-5