Abstract
Starting from an Arabidopsis transgenic line sGsL harboring LUC reporter gene under the control of sugar-inducible promoter (Spomin:LUC), we have previously isolated many mutants exhibiting altered patterns of sucrose-inducible LUC expression. The hsi2 mutant displaying significantly elevated expression of LUC was due to a mutation in a gene encoding a novel transcriptional repressor with the B3-DNA binding domain and EAR repression motif. Co-expression of HSI2 in protoplast transient expression of Spomin:LUC resulted in significantly reduced expression of LUC, and mutation of the EAR motif abolished the trans-repression activity of HSI2. These results suggest that HSI2 binds to Spomin by the B3 domain and repress the transcription initiation via the EAR motif. We are analyzing the DNA binding activity and target site sequence of HSI2 recombinant protein.
