Conserved regions upstream of BRC1B regulate bud dormancy in tomato

Area of Science:

• Plant Biology
• Genetics
• Molecular Biology

Background:

• Plant architecture is significantly influenced by shoot branching, regulated by axillary meristems.
• BRANCHED1 (BRC1) is a key transcription factor controlling bud dormancy by integrating various signals.
• The precise regulation of BRC1 expression, particularly its cis- and trans-regulation, is not well understood.

Purpose of the Study:

• To explore how modifications in the SlBRC1B promoter impact bud outgrowth in tomato.
• To identify regulatory elements within the SlBRC1B promoter that control bud dormancy.

Main Methods:

• Phylogenetic footprinting to identify conserved regions (CRs) in the SlBRC1B promoter.
• CRISPR/Cas9 gene editing to create promoter mutants targeting each CR.
• Bud outgrowth characterization of CR mutants.
• Yeast one-hybrid assay to identify transcription factors binding to CR4.

Main Results:

• Mutations in conserved regions (CR1-CR4) of the SlBRC1B promoter consistently led to decreased bud outgrowth.
• This suggests SlBRC1B expression is tightly controlled by transcriptional repressors.
• Several transcription factor families (MYB, GRF, NAC, MADS, zinc finger) were identified as potential regulators binding to the CR4 region.

Conclusions:

• The identified conserved regions (CRs) are critical for regulating SlBRC1B expression and thus bud dormancy.
• These CRs represent potential targets for manipulating shoot branching in plants.