A fungus that infects corn is finally giving up its secrets. Despite being a long-used tool for studying how plants and microbes interact, researchers had never identified the proteins or other factors that allow the fungal pathogen Ustilago maydis to infect its host. In this week's Nature a group reports it has sequenced the Ustilago genome and found 6,902 genes, including 12 clusters of genes for small proteins that nobody had isolated before. When mutated, five of these clusters turned out to affect the fungus's ability to grow on corn, making them the microbe's first known infection factors.