In wartime, factories shift gears to meet urgent need. Assembly lines repurpose from making car parts to machine guns or from washing machines to airplane engines. Yet, as Duke University professor Xinnian Dong notes, vegetables can also disrupt daily life when conflicts erupt, placing them in harm’s way.
Crops and other plants frequently face attacks by bacteria, viruses, and other pathogens. When a plant senses an invasion, it rewrites the chemical balance inside its cells by altering a vast network of proteins—the molecular workhorses of life.
In recent years, Dong and his team have explored this remarkable response. In a study published in Cell, Dong and first author Jinlong Wang identify key components in plant cells that reprogram the maker of proteins to battle disease.
About 15 percent of crop yields vanish each year due to bacterial and fungal diseases, costing the global economy roughly 220 billion euros. Dong emphasizes that plants rely on an intrinsic immune system to defend themselves.
Unlike animals, plants lack mobile immune cells that travel to an infection site. Every cell must mount a defense, quickly shifting into combat mode when danger arrives.
When plants face a threat, growth is deprioritized in favor of defense. Cells begin producing new proteins while suppressing others. In many cases normal activity resumes within a few hours, as Dong explains.
Thousands of proteins perform duties such as catalysis, signaling, recognition of foreign material, and transport. The genetic blueprint stored in DNA is copied into messenger RNA, which carries the instruction to ribosomes in the cytoplasm. There, the ribosome translates the message into a protein.
In a 2017 study, Dong and colleagues showed that when a plant is infected, certain messenger RNAs are translated into proteins more rapidly than others. They found a common feature among these messenger RNAs: a region at the front end of the RNA sequence with repeating letters in its code.
In the current work, the team demonstrates how this region cooperates with other cellular structures to trigger a wartime mode of protein production.
They show that pathogen detection disrupts the usual signals that recruit ribosomes to start translating messenger RNA, preventing the typical set of “peaceful” proteins from being produced.
Instead, ribosomes bypass the standard starting point and begin reading from an alternative site, using the repeating A and G segments within the RNA. They are effectively using a shortcut, according to Dong.
a risky venture
Fighting infection in plants comes at a cost. Allocating more resources to defense reduces energy available for photosynthesis and growth. Pushing defense responses too far can backfire, leading to stunted development if the immune system stays hyperactive for too long.
Plants face a delicate balancing act: defending against invaders while maintaining growth and productivity. The researchers note that a more aggressive immune state may cause unintended damage, underscoring the need to optimize defense without sacrificing performance.
Understanding how plants strike this balance could enable the development of crops that resist disease without compromising yield or vigor.
Most experiments in this line of inquiry have used mustard-family species, including Arabidopsis thaliana, as a model. Yet the same RNA motifs appear in a variety of organisms, suggesting these mechanisms may influence protein synthesis beyond the plant kingdom and could have parallels in animals as well.
Reference work: a study published in Cell detailing the reprogramming of cellular machinery in plant defense. [Attribution: Dong et al., 2017; Cell]
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