Is it possible to engineer nitrogen fixing nodule symbiosis?

Nitrogen is one of the most important nutrients for plants. However, the availability of nitrogen sources in the soil is often a limiting factor for growth. Some plants, such as legumes, can establish a nitrogen fixing nodule symbiosis with certain bacteria. This allows them to use nitrogen from the air to make ammonium that can be used for their growth. Since the discovery of the nitrogen fixing process at the end of the 19th century, there has been contemplation regarding the possibility of transferring the property of nitrogen fixing root nodule formation to crops that do not have this ability. Currently, our knowledge concerning its evolution and molecular mechanism that control nodulation has markedly increased. In this review, we summarized recent advances in these areas and discussed possibilities to engineer nodulation in crops.