In the mutualistic relationship between legumes and rhizobial bacteria, excessive rhizobia infection inhibits the growth of host plants. Therefore, legumes possess rhizobial inhibition systems in parallel with the system for receiving rhizobia. In Lotus japonicus, the Autoregulation of Nodulation (AON) system via the aboveground parts of the host plant has been shown to play an essential role in suppressing rhizobial infection. In this study, Dr. Akamatsu and his colleagues focused on PITP-like protein (PLP), which encodes a transport protein for phosphatidylinositol whose expression is up-regulated during rhizobial infection. This suggests that the PLP may be involved in the rhizobial suppression system. However, gene expression analysis and double mutant analysis showed that the function of PLP is AON-independent. On the other hand, gene expression analysis suggested that PLP is involved in the local suppression system through the transcription factor NIN, which has been recently revealed. They will clarify the detailed functions of PI and the reasons why rhizobial symbiosis was established with legumes, focusing on PI.