Previous Northern blotting analyses of rice seedlings have screened several WRKY genes among the transcripts that are differentially regulated in the following treatments: high salinity, cold stress, polyethylene glycol (PEG) and heat shock. Here, we report characterization of a WRKY gene, OsWRKY08, in rice, which was found to be inducible by PEG, NaCl, Abscisic acid (ABA), and naphthalene acetic acid (NAA) as its ortholog AtWRKY28 in Arabidopsis. To determine whether overexpression of OsWRKY08 alters abiotic stress tolerance, 35S::OsWRKY08 recombinant was generated and transformed into Arabidopsis. Physiological tests indicated that 35S::OsWRKY08 transgenic Arabidopsis displayed increased tolerance to mannitol stress through increasing the lateral root number and primary root length during seeding root development. Further, semi-quantitative RT-PCR showed that AtCOR47 and AtRD21, two ABA-independent abiotic stress responded genes, were induced in 35S::OsWRKY08 transgenic plants. These results suggest OsWRKY08 improves the osmotic stress tolerance of transgenic Arabidopsis through an ABA-independent signaling pathway.
Rice is a model plant for genomic study of grass species. Functional identification and definition of rice genes becomes the object of its functional genomics research. WRKY gene superfamily, one of the transcription factor gene families, was recently suggested to play important roles in plant development and stress response. In rice, the results of analyses of expression pattern and ectopic overexpressor lines also support this viewpoint, and the evidences implicate rice WRKY proteins in transcriptional reprogramming during biotic or abiotic stresses, senescence, sugar metabolites, and morphological architecture. In this paper, we review the advance in study of rice WRKY gene family and also propose unified nomenclature for rice WRKY factors to eliminate confusion.
