Functional Analysis of Lotus japonicus Transcription Factors Identified in Transcriptome Analyses of the Nodulation Process

Abstract

Transcriptome analyses of the model legume Lotus japonicus by cDNA array (Kouchi et al. 2004) and SAGE (Asamizu et al. 2005) have led us to identify twenty transcription factors (TFs) whose expression is up regulated in the nodulation process. Expression profile of the TFs was analyzed quantitatively by realtime RT-PCR. We found expression of seven TFs was induced as initially as 3 hrs after the Mesorhizobium loti inoculation. We observed expression of three of the early responding TFs was affected in symRK but not in nin plant, indicating a possibility that induction of these TFs takes place prior to the NIN activation. We obtained nodulation-defective mutants for one ERF gene by screening the Lotus TILLING line. Overexprssion of this gene in transformed hairyroots resulted in significant increase of nodule number compared to non-overexpressed vector control. We are focusing on this gene to elucidate its function using the erf mutated plant.