Verticillium dahliae is a serious fungal disease that kills many important crops like cotton and tomato by clogging their water-conducting vessels. Scientists discovered a protein called VdKeR1 that helps this fungus grow and cause disease by controlling how it makes ergosterol, a crucial component of fungal cell membranes. When researchers removed this protein, the fungus grew poorly, couldn’t form survival structures, and was much less dangerous to plants.