Differential Regulatory Mechanisms of CBF Regulon Between Nipponbare (Japonica) and 93-11 (Indica) During Cold Acclimation

Nine CBF/DREB1 homologous genes in rice were obtained by BLAST search in the NCBI database, which share conserved amino acid sequences with DREB1 protein in Arabidopsis. Three CBF genes organized in tandem, named OsCBF1, OsCBF2 and OsCBF3, showed a transient induction in the process of cold acclimation, much stronger in indica rice 93-11 compared with japonica rice Nipponbare. The candidate downstream genes OsLIP5 and OsLIP9 were induced in 93-11 but not in Nipponbare. The differential expression of CBF regulon might be caused by polymorphisms within promoter sequences between these two rice varieties. These results could be useful for utilization of CBF/DREB1 genes and illustration of differences in chilling tolerance between indica and japonica rice varieties.