In times of conflict, factories reorganize to support the war effort. Assembly lines change course from turning auto parts into machine guns or from building washing machines to airplane engines.
Plants are often attacked by bacteria, viruses and other pathogens, similar to what happens in a real war. When a plant senses a microbial invasion, it makes radical changes in the “chemical soup” of proteins inside its cells.
In recent years, Xinnian Dong, a professor at Duke University, United States, and his team have learned the secrets of this process. In a new study published in Cell magazineDong and first author Jinlong Wang reveal the key components in plant cells that reprogram their protein factories to fight disease.
How do plants adapt?
Every year, about 15% of the crop is lost to bacterial and fungal diseases, costing the global economy about $220 billion. Plants rely on their immune system to help them fight, Dong said.
Unlike animals, plants do not have specialized immune cells that can travel through the bloodstream to the site of infection. Every cell in the plant must be able to stand up and fight to defend itself, quickly going into battle mode. When attacked, plants change their priorities from growth to defense, so the cells begin to synthesize new proteins and suppress the production of others. Then “within two to three hours things are back to normal,” Dong said.
What happens when plants are infected?
The tens of thousands of proteins produced in cells perform many tasks: catalyzing reactions, serving as chemical messengers, recognizing foreign substances, moving materials in and out. To build a specific protein, the genetic instructions in the DNA packaged in the cell’s nucleus are transcribed into a messenger molecule called mRNA. This strand of mRNA then moves into the cytoplasm, where a structure called a ribosome “reads” the message and translates it into a protein, indicates Eurek Alert.
In a 2017 study, Dong and her team found that when a plant is infected, certain mRNA molecules are converted into proteins faster than others. What these mRNA molecules have in common, the researchers found, is a region at the front end of the RNA strand with recurring letters in its genetic code, where the nucleotide bases adenine and guanine repeat over and over. In the new study, Dong, Wang and their colleagues show how this region interacts with other structures inside the cell to activate the production of “wartime” proteins.
The “offensive system” of plants
The team showed that when plants detect a pathogen attack, the molecular cues that signal the usual starting point for ribosomes to land and read mRNA are removed, preventing the cell from making its typical “peacetime” proteins. “. Instead, ribosomes bypass the usual starting point. “I’m basically taking a shortcut,” Dong said.
For plants, fighting infection is a balancing act, Dong said. Allocating more resources to defense means less is available for photosynthesis and other activities.
Producing too many defense proteins can create collateral damage: plants with an overactive immune system experience stunted growth. By understanding how plants achieve this balance, Dong said, scientists hope to find new ways to create disease-resistant crops without compromising yield.