Fungal Proteins: The Double Agents in Plant Infections

In the world of plant diseases, some proteins are like secret agents. They have a double life. They help the fungus cause disease. But they also wake up the plant's defense system. Scientists found six such proteins in a fungus called Verticillium dahliae. These proteins belong to a family known as GH7. First, the scientists removed each GH7 protein from the fungus. They saw that the fungus became less harmful. But it grew just fine. This showed that these proteins help the fungus cause disease. But they are not needed for the fungus to grow. Next, the scientists wanted to see where these proteins go. They used special tools to watch the proteins in action. They saw that the proteins move into the plant cells. They end up in the cytoplasm. This is the fluid part of the cell. Once there, they trigger the plant's defense system. The plant's defense system is like an alarm. It causes a few things to happen. First, some plant cells die quickly. This is called hypersensitive cell death. Second, the plant makes special molecules. These molecules help fight off the fungus. Third, the plant makes a substance called callose. This helps block the fungus from spreading. The scientists also wanted to know how the plant knows to turn on its defense system. They found that two special proteins in the plant are important. These are called SGT1 and NDR1. If these proteins are not working, the plant does not react to the GH7 proteins. This shows that the GH7 proteins trick the plant into turning on its defenses. This is a big deal. It shows that some proteins can have two jobs. They can help the fungus cause disease. But they can also help the plant fight back. It's like a game of chess. The fungus and the plant are always trying to outsmart each other. This discovery gives us a new piece of the puzzle. It helps us understand how plants and fungi have evolved together.