The Role of the BELL1-2 Transcription Factor in the Development of Legume-rhizobial Symbiosis

Nodule development is a process that is tightly regulated by phytohormones, mainly gibberellins and cytokinins. During nodule development gibberellins and cytokinins play an important role in the infection development and organogenesis. However, the interaction between these phytohormones is not yet clear. In our research we first demonstrated that the BELL1-2 transcription factor can influence gibberellin and cytokinin biosynthesis genes during nodule development. It was also found that BELL1-2 can regulate SHY2-like gene which is specifically involved in the control of meristem maintenance and organogenesis. Localisation of the expression of the pMtBELL1-2::GUS promoter showed that the gene is expressed in the primordia, as well as in the infection zone and the nitrogen-fixing zone of mature nodules. Furthermore, we detected an increase in the infection zone in M. truncatula nodules with BELL1-2 RNAi due to the modified growth of the infection threads. In summary, we conclude that BELL1-2 plays an important role in the control of infection and organogenesis in legume plants.