Intragenic suppressors unravel the role of the SCREAM ACT-like domain for bHLH partner selectivity in stomatal development
Hyemin Seo, Krishna Mohan Sepuru, Aarthi Putarjunan, Lyndsey Aguirre, Benjamin Burrows, Keiko U. Torii
Abstract
Significance Whether animal neurons or plant cellular valves (called stomata), specialized cell-type differentiation is directed by the lineage-specific basic helix–loop–helix (bHLH) transcription factors that typically form heterodimers with ubiquitous bHLH proteins. How does a broadly expressed bHLH protein switch its lineage-specific heterodimeric partners? Here we identify a structural module, called the ACT-like domain, in the plant bHLH protein SCREAM. This domain plays a role in partner bHLH selectivity and is critical for the proliferation-to-differentiation switch within the cell lineages to make stomata, plant cellular valves for gas exchange and water control. Our work provides mechanistic insight into how plant transcription factors control cell-fate specification through an unanticipated heterodimeric partner selectivity interface.