Scientists are trying to engineer non-legume crop plants, such as corn, wheat, and rice, to form symbiotic relationships similar to the legume-Rhizobium relationship. But this has proven to be a very difficult task. At each step of nodule formation, plant genes must be expressed that enable the plant to respond appropriately to the bacteria. For a non-legume plant to form a symbiotic relationship with rhizobia, it would need to be engineered with the right genes and then express those genes at exactly the right time. In this activity, you will identify the steps of nodule formation in the legume-Rhizobium relationship. In addition, you will indicate what the products of genes added to a non-legume plant would need to do in order to carry out each step.