Regulates tillering and panicle branching by modulating SPL14/IPA1 transcriptional activity on the downstream TB1 and DEP1 target genes (PubMed:30914468). Binds directly to the 5'-T/GCTCTAC-3' DNA motif found in the promoter regions of both TB1 and DEP1 (PubMed:30914468). Represses the DNA binding activity of SPL14/IPA1 toward the promoters of both TB1 and DEP1 (PubMed:30914468). Exhibits weak transcriptional activation activity in yeast cells (PubMed:30914468). Forms homodimers (via C-terminus) (PubMed:30914468). Interacts with SPL14/IPA1 (via C-terminus) (PubMed:30914468). Predominantly expressed in axillary buds and young panicles. Significant reduced tiller number, enhanced culm strength, increased panicle branch numbers and reduced grain size. Belongs to the SHI protein family.