Abstract
Rice transcription factor WRKY45 plays a central role in chemical-induced resistance through salicylic-acid pathway. Transgenic rice plants overexpressing WRKY45 driven by maize ubiquitin promoter exhibited strong multi-diseases resistance to blast and leaf-blight diseases. However, they showed growth retardation and yield decrease, which hampers their practical application. To optimize WRKY45 expression in regard to disease resistance and agricultural traits, we generated several rice lines overexpressing WRKY45 driven by various promoters.
We isolated 2-kb upstream sequences of 22 genes with various expression characteristics, fused them upstream of WRKY45 cDNA, and introduced the constructs into rice. Among transformants, those that express WRKY45 under the control of OsUbi1, EF1α, OsUbi7 (POsUbi7) promoters exhibited enhanced resistance to both blast and leaf-blight diseases, as well as improved agricultural traits. Especially, POsUbi7:WRKY45 lines exhibited agricultural traits roughly comparable to those of non-transgenic line in a greenhouse whose conditions follow external ones. These results make them promising candidates for practical application.
