Isolation and characterization of a novel GRAS gene that regulates meiosis-associated gene expression.

GRAS protein is a family of plant-specific proteins that plays a role in various developmental processes. Here we report a novel GRAS protein from lily, designated LlSCL (Lilium longiflorum Scarecrow-like), dominantly expressed at the premeiotic phase within anthers. The LlSCL protein has two highly basic regions, and transient expression analyses of dissected GFP-LlSCL fusion proteins showed that both basic regions are important for the nuclear localization. A series of transcriptional activation experiments of truncated LlSCL proteins fused to the yeast GAL4 DNA-binding domain clearly demonstrated that the amino terminus of the LlSCL protein has a strong activity of transcriptional activation in the yeast as well as in the plant cell. Further investigation on the effect of the LlSCL protein on the transcriptional activity of the meiosis-associated promoter revealed that in pollen mother cells of the lily, the activity of the meiosis-associated promoter is specifically enhanced by LlSCL protein co-expression. These results suggest that LlSCL is involved in transcriptional regulation during microsporogenesis within the lily anther.