Nuclear localization and target genes analysis of an ABA and drought-responsive transcription factor (RDA1) in rice

Apetala2/Ethylene Responsive Factor (AP2/ERF) family transcription factors (TFs) play an important role in controlling cellular processes and regulating important functions of plant growth and development as well as responses to environmental stimuli. AP2/ERF transcription factor responsive to drought and ABA (RDA1) from rice genotype N22 was chosen for this study. Transient expression revealed that RDA1 was localized in the nucleus. Quantitative expression studies of RDA1 under three different treatments namely drought, ABA and drought + ABA at three different stress levels showed maximum expression (3.92 fold) under drought +ABA treatment. Further, higher expression was found in N22 (drought tolerant) compared to IR 64 (susceptible) at different stress levels. Temporal expression revealed higher relative expression in leaf tissue compared to root tissue in both cultivars. RDA1 acts as a cytokinin primary response gene as per in silico characterization and many of its target genes are involved in transcriptional, post-transcriptional and translational regulation of protein biosynthesis. Relative co-expression studies for target genes revealed positive co-expression of GAMYB-binding protein, leucyl tRNA synthetase and negative co-expression of ribosomal protein L7, crooked neck (CRN) protein and XPA-binding protein with RDA1. Differential co-expression of WD40 and DUF382 domain protein was observed in root and leaf tissue with RDA1.