By Diana Horvath
In the case of SARS-Cov-2, virus particles highjack human cells and trick them into becoming virus factories, establishing an infection (leading to Coronavirus Disease 2019, COVID-19) before the human host mounts an immune response.
Plants are also sickened by viruses and other pathogens, with fungi and oomycetes (also known as water molds) being the most damaging.
When attacked by pathogens, the host usually detects the intrusion and activates its defenses to fight off the invaders. In people, a cornerstone of this system of immunity are antibodies that can adapt to identify new pathogen threats and mark them so other parts of the immune system can attack.
Sometimes a person’s immune reaction is not quick or strong enough after becoming infected, and they get sick and may die. In some cases, scientists have developed drug therapies that can bolster the immune response and help the host win the battle—like the anti-retroviral cocktail (a mix of anti-viral drugs) used to fight HIV. This approach effectively and durably prevents the virus from reproducing itself by three distinct mechanisms, making it far less likely that the virus that can overcome the drugs.
If a plant can’t recognize a predator it might not fight back
Plants don’t make antibodies but do have an immune system of pathogen detectors that activate strong cellular defenses against known threats. But there are new and existing pathogens for which they have no detector, and they don’t have the same adaptive immune system that people have. If a plant can’t recognize a predator, it may not know it’s in danger—and might not fight back quickly or strongly enough, if at all.
But scientists can bolster plant immunity too. Scientists can identify the detectors that recognize pathogens—also known as receptors or resistance proteins—and combine them to trigger robust protection from disease, much like a vaccination.
And there are now multiple tools to find more plant pathogen resistance proteins—by looking in nature within the genomes of crops like corn, wheat, or potatoes and their domesticated and wild relatives. Scientists can then introduce the genes for these resistance proteins into a crop to protect it from its worst unmanaged diseases. Combining multiple mechanisms like a therapeutic cocktail, this approach supplements the plant’s own immune system for long-lasting protection.
A new safe and effective pathway to protect our food crops
The 2Blades Foundation and its collaborators have shown that providing additional resistance proteins to plants leads to strong reductions in the amount of pathogen in the plant, without using any chemical pesticides.
Because these receptors are introduced directly into a host genome, the intervention is like a vaccination and the crop is potentially protected from that disease for the rest of its life. Yet it is better than a vaccination since this protection is passed on to future generations of crops.
Pathogens do evolve and change, but by studying the races of pathogens in existence and combining multiple receptors together, it is possible to build resistance that can last through many generations of crops over many years.
Still fighting the same wheat diseases that the Romans battled
Protecting plants in this way is not new. It’s the same process that nature uses to adapt to new diseases—but in nature it’s a brutal process of selecting only those individuals that survive and thrive. Farmers and breeders have expanded on this process of selection to produce our modern crops while combining the best traits for productivity, taste, drought tolerance, etc.
Wheat stem rust (a type of fungus), is among the world’s most devastating plant diseases—dating back to the Roman Empire—and resistant varieties are the most effective and environmentally benign means to control it. This recurring threat to wheat had been managed through the development of stem rust-resistant varieties developed by conventional breeding and grown widely during the Green Revolution of the 1960s. However, recently evolved strains of the stem rust pathogen can attack these wheat varieties and again threaten harvests.
Starting about 100 years ago, Sir Rowland Biffen began the process of conventional breeding and selection to produce rust-resistant wheat, and that process is still used by breeders to combine or “pyramid” multiple genes in a crop—to produce a built-in “cocktail” of resistance. However, conventionally bred pyramids draw on genes spread throughout the plant’s genome. These can become separated from each other when bred for new traits, making it challenging to maintain rust resistance in new wheat varieties.
“Vaccinating” our food crops to protect future generations from food insecurity
Recently, Nature Biotechnology published new 2Blades-coordinated research through which wheat varieties were developed that are durably resistant to devastating rust diseases costing farmers and consumers nearly $3 billion each year.
The research team, led by Australia’s national science agency CSIRO, used novel genetic technologies to insert a “stack” of five rust resistance genes into a single location in the genome of a common wheat variety. This new wheat variety has been shown to be much more resistant to rust fungal pathogens which rapidly evolve to overcome the plant’s defenses. It could also save years of effort and ensure this desirable trait will not be lost in subsequent breeding generations.
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