A rice bZIP transcription factor, OsbZIP16, regulates abiotic stress tolerance when over-expressed in Arabidopsis

Plants exposed to adverse environmental conditions are invariably compromised in their growth and development. The bZIP class of transcription factors (TF) form a large group among stress signalling components that regulate plant responses towards stress. We identified bZIP TF encoding genes that are expressed differentially in indica rice under stress and here we functionally characterize one such gene, OsbZIP16. Although, OsbZIP16 forms a clade with its orthologous monocot protein sequences, we find in our study that it can impart tolerance to abiotic stress in Arabidopsis. OsbZIP16 is expressed strongly upon dehydration, salt and ABA treatment in Oryza sativa cv. IR64 seedlings. It localizes in the cell nucleus and the gene product is capable of transcriptional activation, thus providing evidence for its capability as a functional TF. Upon overexpression in Arabidopsis, OsbZIP16ox plants show wild type morphology, however, these plants showed tolerance when subjected to drought stress at vegetative stage and set healthy seeds on recovery. The OsbZIP16ox seedlings showed reduced sensitivity to mannitol, ABA and sodium chloride during germination and also reduced ROS accumulation upon H2O2 exposure. Thus, OsbZIP16 regulates abiotic stress responses and is also a good candidate gene that can be utilised to impart tolerance in plants under water deficit conditions.