Branched1

branched1 is the name used for a family of plant genes that regulate shoot branching. The best characterized member is BRANCHED1 (BRC1) in the model plant Arabidopsis thaliana, a TCP transcription factor that acts as a central suppressor of axillary bud outgrowth and thereby shapes branching patterns.

BRANCHED1 is expressed in axillary buds and adjacent stem tissue. When active, it promotes a dormant bud state and limits outgrowth. The gene sits downstream of strigolactone signaling and is modulated by hormonal and environmental cues: strigolactones tend to upregulate BRC1, while cytokinins and favorable sugar status counteract its action to promote bud growth. Auxin export from the main shoot apex indirectly influences BRANCHED1 by regulating strigolactone production.

Loss-of-function brc1 mutants show increased branching, whereas overexpression of BRANCHED1 reduces branching and can suppress bud outgrowth even under conditions that normally promote it.

Branched1 has several homologs across angiosperms, including Teosinte Branched1 (TB1) in maize and OsTB1 in rice, which regulate tillering and panicle architecture respectively. Across species, branched1 family members contribute to domestication and diversity of plant architecture by affecting the balance between active and dormant buds.

Molecularly, branched1 encodes a TCP transcription factor of class II. TCP proteins are plant-specific DNA-binding regulators; BRANCHED1 localizes to the nucleus and interacts with other regulators to control transcription in shoot–bud tissue.